Mastering audio

[Light Dependant Resistor]

What is mastering audio, and how does it relate to audiophiles ? In this brief tour you will find me praising the use of companding that should IMO be commonplace for audiophiles as means to achieve higher performance from audio equipment. Companders can be used real time if two stereo channels are available, one switched for compression and the other for expansion. Or can be
used with a recording device where recordings are compressed then expanded upon playback.

You may have seen remastered copies of your favourite recordings, or like the work of a particular mastering engineer. But what do they do , and how do they do it?

A mastering engineer is not usually a person who mixes recordings, ( although it would probably help a lot if they did ) rather they strive to source untouched best editions of recordings, and try to understand the intention of the musician, and consult with the musician if he or she is available how the pieces or pieces were to sound, to attempt subtle or higher improvement.

Just what is a good recording ? If you own a copy of Ron Carters Picolo you will appreciate
how good a recording can get, here the microphones in 1977 must have been in all the right places, and the musicians were really enjoying what they were doing. All analog and simply amazing !

Whilst some engineers today are comfortable with computer plugins others prefer dedicated hardware such as products made by Dbx, TC , Apogee, Neve, Waves, to name a few.

Common terminology is attack, hold, release, compression, expansion/gate, compression and expansion ratio's, sidechain eq and limiting and de essing. Each of these is well understood by
the mastering engineer, and when to use and more importantly when not to use. Whilst just
reading these suggests that these would alter the sound wrongly the opposite is actually true,
if used carefully and knowing when to stop.

Where a mix of a recording has individual channels for say bass guitar, drums, and vocals a mastering engineer may find a better balance of how those instruments should sound, or
where a recording is provided complete, improvement in how it sounds.
The engineer may for example make small changes to the hold and release times that greatly benefits the perceived sound, as though the music now has much greater freedom.

Here is a article about a tour of ECM Rainbow studios, and its engineer Jan Erik Kongshaug
http://www.allaboutjazz.com/norwegian-road-trip-part-4-oslo-and-an-interview-with-jan-erik-kongshaug-by-john-kelman.php

Jan has certainly had a very fortunate working life, proudly engineering some of the best recordings ever made.

Gathering some knowledge of how mastering occurs can greatly assist audiophiles, if they too want
to delve into daily minor remastering of their own LP or CD collection, or just to appreciate what the mastering or recording engineer achieved.

The findings and life long work of Davd Blackmer steer toward exploring extended frequency response from equipment, and analysis of distortions occurring as a result of spatial time not being
properly adjusted or allowed for properly in high fidelity equipment. Some good examples of
excellent attempts at improving spatial time with speakers are the Quad ESL 57 and 63 , and in conventional speakers alignment of drivers like the B & W 801,802 and others.

David Blackmers invention of the DBX noise reduction system can easily be shown to extend the dynamic range of recordings, and suggests that a lot of what DBX does with products, also attempts to correct time distortions. Using companding that is having settings for compression and opposite but not necessarily exactly opposite settings for expansion the recording device is unburdoned from handling peaks. This allows recordings when then expanded on playback to to seemingly and sometimes dramatically improve perceived sound. But Why ? Removing the dynamics by compression but then restoring by expansion has foundation in work done by Murray Crosby where it was shown great benefit in signal to noise ratio is achieved with pre and post networks when added to a signal namely emphasis and de-emphasis for FM radio. Similarly Dolby was/ is another type of circuit using frequency addition during recording and deduction during playback

Although analog companding is exceptional and is usually the single best investment you can make to a audio system, it has promise to be better still where companding is done in the digital domain, and here a recording device like a flac or wav dedicated audio recorder can be the medium where storage of compressed digital is done.

Many on the forum would know of my work with Light Dependant Resistors, and these show
subtle characteristics of expansion with the series ldr and compression with the shunt, possibly
why they breathe new life into recordings

Companding generally has great benefit for audio reproduction, particularly where a recording device
is utilized to hold compressed audio and hardware or software releases that audio captured in a expanded state.

Cheers / Chris

[awkwardbydesign]

IIRC, DBX companders were available in the 80s. Didn't they suffer from "breathing"? ie. the noise floor rising and falling? Especially if multitracking was involved?

[Lodgesound]

IIRC, DBX companders were available in the 80s. Didn't they suffer from "breathing"? ie. the noise floor rising and falling? Especially if multitracking was involved?

Yes they did indeed - Dolby was a far superior system which utilised "null frequencies" for type A and "masking" for type SR.

Properly aligned Dolby A or SR chains carry no audible artifacts in their operation.

[PaulStewart]

As someone who has been a recording engineer, producer and some time mastering engineer, I have to disagree, DBX used as a noise reduction system sucked, the domestic version used on JVC cassette decks in conduction with their version of Dolby B, Super ANRS, sucked worse. DBX have however made some fine compressors. Dolby A was OKish for things like chamber music, but as they said in Spinal Tap "Everyone knows you can't record Rock in Dobly".

My experience was that a good tape, my fav was Agfa PEM 468, which was capable of a high signal level well above the noise floor and that did not exhibit too much tape compression was way, way better. However Dolby SR was/is, if properly aligned, etherial, the thing that still blows me away about it, is fade endings and decay. Where DBX would pump, Dolby A would crunch and digital would alias, SR just faded away. Pity that digi came in and blew it away.

[Lodgesound]

As someone who has been a recording engineer, producer and some time mastering engineer, I have to disagree, DBX used as a noise reduction system sucked, the domestic version used on JVC cassette decks in conduction with their version of Dolby B, Super ANRS, sucked worse. DBX have however made some fine compressors. Dolby A was OKish for things like chamber music, but as they said in Spinal Tap "Everyone knows you can't record Rock in Dobly".

My experience was that a good tape, my fav was Agfa PEM 468, which was capable of a high signal level well above the noise floor and that did not exhibit too much tape compression was way, way better. However Dolby SR was/is, if properly aligned, etherial, the thing that still blows me away about it, is fade endings and decay. Where DBX would pump, Dolby A would crunch and digital would alias, SR just faded away. Pity that digi came in and blew it away.


Hi Paul;

I love SR personally also - so clean and smooth.

Which open reel machines did you master to for supply to the cutting houses?

[Light Dependant Resistor]

As someone who has been a recording engineer, producer and some time mastering engineer, I have to disagree, DBX used as a noise reduction system sucked, the domestic version used on JVC cassette decks in conduction with their version of Dolby B, Super ANRS, sucked worse. DBX have however made some fine compressors. Dolby A was OKish for things like chamber music, but as they said in Spinal Tap "Everyone knows you can't record Rock in Dobly".

My experience was that a good tape, my fav was Agfa PEM 468, which was capable of a high signal level well above the noise floor and that did not exhibit too much tape compression was way, way better. However Dolby SR was/is, if properly aligned, etherial, the thing that still blows me away about it, is fade endings and decay. Where DBX would pump, Dolby A would crunch and digital would alias, SR just faded away. Pity that digi came in and blew it away.

The domestic version Type 2 you describe was designed for cassette and cartridge machines where it no doubt did a good job. Like holding the banner for Dolby with Type B as their best, its unfair to similarly think Type 2 as being the be all and end all of DBX. Given sound as we know it can be said to contain signal noise and distortion. Type 1 DBX noise reduction as seen in many products including the 150x 155, 180a offered more noise reduction than anything Dolby could do in companding, including Dolby A.

Can a type 1 DBX noise reduction unit designed in the latter years of 15 ips and 30 ips tapes, be applicable to say improving playback of CD or LP today ?. I already know the answer, and it is a unreserved Yes
I know of 3 persons other than me doing exactly this with a 150x and will kindly ask them to submit their comments.

I am investigating digital companding, with review of a DBX DDP, and Quantum which show much promise in tandem with a yamaha CDR HD1500, but the 150x has a very analog sound to it, that is hard to beat.

Cheers / Chris

[PaulStewart]

Hi Paul;

I love SR personally also - so clean and smooth.

Which open reel machines did you master to for supply to the cutting houses?

Studer A80 and an Otari I forget the model number of now :) getting old I guess :lol: As I posted on here recently, I just bought a couple of PR99s for my new "Analogue Blues Project" This involves an old analogue mixer, some mics and straight to stereo. Should be wild.

[petrat]

This is all very interesting.
I'm afraid I have no knowledge about anything being discussed, but just wanted to ask if anyone knew of a book/article/web-page where I could learn more about the whole recording process, particularly the history aspect?
Sorry for the hi-jack, but it's threads like this, and the knowledge of contributors, that make this place so useful IMO. :clap:

[Rothchild]

This is all very interesting.
I'm afraid I have no knowledge about anything being discussed, but just wanted to ask if anyone knew of a book/article/web-page where I could learn more about the whole recording process, particularly the history aspect?
Sorry for the hi-jack, but it's threads like this, and the knowledge of contributors, that make this place so useful IMO. :clap:

Sound on Sound have a good series on classic recordings with the engineers, good for an overview of how various artists and studios have worked over the years: http://www.soundonsound.com/search?Keyword=classic+tracks

I think an understanding of loudness standards (eg LUFS / EBU ) is also now a crucial part of understanding the role of a mastering engineer lots of countries now have rules and standards about loudness so getting this stuff right is important (as would have been understanding how to manipulate an RIAA curve when pressing to vinyl 'back in the day')

[PaulStewart]

This is all very interesting.
I'm afraid I have no knowledge about anything being discussed, but just wanted to ask if anyone knew of a book/article/web-page where I could learn more about the whole recording process, particularly the history aspect?
Sorry for the hi-jack, but it's threads like this, and the knowledge of contributors, that make this place so useful IMO. :clap:

The late John Borwick wrote a book in conjunction with the Association of Professional Recording Studios, called Sound Recording Practice. It's a bit of a tome, but gives a very good insight. I believe it is still available, but I've seen second hand copies.

[Audio Advent]

For modern studio engineer talk (and some top names on there) you could look at the gearslutz forum. Obviously a lot of amateurs in there too but lots of discussion of techniques of yesteryear so people can recreate the past.

I followed a link on that forum to a page giving real world frequency responses of some of the best regarded tape machines as measured by an experienced producer/mastering engineer and was very surprised at how bad they were, some supposedly after alignment. Obviously more to the sound than flat frequency responses.

[petrat]

Thanks for the suggestions fellas ... I'll certainly be checking those out soon :christmas:

[PaulStewart]

For modern studio engineer talk (and some top names on there) you could look at the gearslutz forum. Obviously a lot of amateurs in there too but lots of discussion of techniques of yesteryear so people can recreate the past.

I followed a link on that forum to a page giving real world frequency responses of some of the best regarded tape machines as measured by an experienced producer/mastering engineer and was very surprised at how bad they were, some supposedly after alignment. Obviously more to the sound than flat frequency responses.

Gearslutz can be really interesting. The chap who bought our custom built Midas desk from Tin Pan Alley Studios is on there. He is restoring it in a barn in Essex. I'm hoping touse it again when he's finished it :)

[Light Dependant Resistor]

For modern studio engineer talk (and some top names on there) you could look at the gearslutz forum. Obviously a lot of amateurs in there too but lots of discussion of techniques of yesteryear so people can recreate the past.

I followed a link on that forum to a page giving real world frequency responses of some of the best regarded tape machines as measured by an experienced producer/mastering engineer and was very surprised at how bad they were, some supposedly after alignment. Obviously more to the sound than flat frequency responses.

The basics of recording are wanted signal, and to make minimal noise and distortion which is why most mastering today tries to source the best possible recording. The essence being that the quietest signal remains above the noise, and the loudest signal remains below where distortion occurs. Whilst analog tape 15 ips or 30ips is forgiving with peaks, digital is not.

In both analog and digital recording and mastering their is much advantage in companding, which improves signal to noise ratio.

[PaulStewart]

In both analog and digital recording and mastering their is much advantage in companding, which improves signal to noise ratio.

Only if the companding doesn't introduce more audible artefacts than it covers, analogue companding such as dbx is pants. It pumps and breathes like an asthmatic whose lost his inhaler, which is why when both were available Dolby A kicked it's arse in the recording/mastering world. To be honest Dolby A was bad for different reasons too, in most studios I used that had Dolby I switched it out, espesially on drums and rhthym sections if I used it at all. I never used Dolby A on the stereo master ever. SR on the other hand was great, but too late in the game.

With digital mastering the dynamic range is already way above the noise floor so to get full range punchy, quiet recordings, you just adhere to the convention that digital zero = -7db, it ain't rocket science and you need neither plug ins or, out of date hardware that was rubbish when new to get good mastering.

[Light Dependant Resistor]

Only if the companding doesn't introduce more audible artefacts than it covers, analogue companding such as dbx is pants. It pumps and breathes like an asthmatic whose lost his inhaler, which is why when both were available Dolby A kicked it's arse in the recording/mastering world. To be honest Dolby A was bad for different reasons too, in most studios I used that had Dolby I switched it out, espesially on drums and rhthym sections if I used it at all. I never used Dolby A on the stereo master ever. SR on the other hand was great, but too late in the game.

With digital mastering the dynamic range is already way above the noise floor so to get full range punchy, quiet recordings, you just adhere to the convention that digital zero = -7db, it ain't rocket science and you need neither plug ins or, out of date hardware that was rubbish when new to get good mastering.

Sadly you appear to have never owned a type 1 DBX as none of these problems occur with it, and it is extremely good at improving playback. whilst designed for the latter days of analog tape recording, its a great sounding device to improve today's CD playback, as it can be used real time without a recording device.

With digital recording holding level back yes has to be done, which as nice as digital recording can be, it compromises signal to noise ratio ( with having less signal ) and thankfully is exactly where a good digital interface compatible compander can assist to all but remove noise.

[PaulStewart]

Chris, my experience with dbx goes back to the 70s, when I was at JVC we looked at various types of noise reduction, even experimenting with dbx encoded LPs, which were rubbish BTW. We ended up as I have said before with Super ANRS, this was JVC's proprietory system the combined their version of Dolby with their version of dbx. It was passable but was always bettered by using a good tape such as TDK SA or even better MA or other pure metal tape, turning all N/R off and the wick up.

As for type 1 dbx at Village Way Recorders, we had a complete set of K9 cards for the Dolby frame. The last time I saw them, they were in a cardboard box slung in a cupboard, because, they were crap and we tried to sell them and nobody was interested in thevpro market for the same reason. The fact is mate, dbx had to re invent themselves as an outboard compressor maker because their N/R system was a failiure. Believe me if it had of worked without wheezing we would have used it.

[Macca]

Using DBX screwed up Steely Dan's 1975 album 'Katy Lied':

http://en.wikipedia.org/wiki/Katy_Lied

[PaulStewart]

Using DBX screwed up Steely Dan's 1975 album 'Katy Lied':

http://en.wikipedia.org/wiki/Katy_Lied

Yes and a lot of other recordings from that time :( just had a listen to Katy Lied and yes you can still hear it breathing away. From a technical point of view, it's just not fast enough to be inaudible, the only one that did work(ish) was NICAM and that had other problems of it's own.

[Light Dependant Resistor]

Chris, my experience with dbx goes back to the 70s, when I was at JVC we looked at various types of noise reduction, even experimenting with dbx encoded LPs, which were rubbish BTW. We ended up as I have said before with Super ANRS, this was JVC's proprietory system the combined their version of Dolby with their version of dbx. It was passable but was always bettered by using a good tape such as TDK SA or even better MA or other pure metal tape, turning all N/R off and the wick up.

As for type 1 dbx at Village Way Recorders, we had a complete set of K9 cards for the Dolby frame. The last time I saw them, they were in a cardboard box slung in a cupboard, because, they were crap and we tried to sell them and nobody was interested in thevpro market for the same reason. The fact is mate, dbx had to re invent themselves as an outboard compressor maker because their N/R system was a failiure. Believe me if it had of worked without wheezing we would have used it.

Hi Paul
Some notes from a recording of the Grateful Dead about using the K9 cards,
http://userpages.umbc.edu/~hamilton/Sources/gd770508eaton.txt

I recently re-decoded 5/5/77 and 5/8/77. I went into Right Track Studios in NYC (my home base studio ) set up in studio B (which is the premier state of the art Digital Music Studio in world). I had clean dat copies (provided by Tim Daulton) that were NOT decoded. I set up a chain consisting of: Panasonic Sv4100 AES out-->DB Technologies 924AD (24bit/96k capability)-->Dolby 361 Modules w/DBX K9-22 cards-->Neve Capricorn 32bit point processing/full 24bit Digital Console-->DB Technologies 122s 24bit/16bit conversion and 44.1k/48k sample rate conversion-->Panasonic Sv4100 Dat AES in. This is State of the Art Tchnology, getting as much of the music that was on the tapes as possible. The thing about DBX that nobody else got is that in order to decode it properly the volume into the decoder has to be exact, otherwise the tapes can be to bass heavy or to bright and compressed. These tapes are absoultly the best possible reproductions of the dig tapes made from the masters (I only wish I had the actual reels so I could do a proper azimuth adjustment on them).

[PaulStewart]

Hi Paul
Some notes from a recording of the Grateful Dead about using the K9 cards,
http://userpages.umbc.edu/~hamilton/Sources/gd770508eaton.txt

I recently re-decoded 5/5/77 and 5/8/77. I went into Right Track Studios in NYC (my home base studio ) set up in studio B (which is the premier state of the art Digital Music Studio in world). I had clean dat copies (provided by Tim Daulton) that were NOT decoded. I set up a chain consisting of: Panasonic Sv4100 AES out-->DB Technologies 924AD (24bit/96k capability)-->Dolby 361 Modules w/DBX K9-22 cards-->Neve Capricorn 32bit point processing/full 24bit Digital Console-->DB Technologies 122s 24bit/16bit conversion and 44.1k/48k sample rate conversion-->Panasonic Sv4100 Dat AES in. This is State of the Art Tchnology, getting as much of the music that was on the tapes as possible. The thing about DBX that nobody else got is that in order to decode it properly the volume into the decoder has to be exact, otherwise the tapes can be to bass heavy or to bright and compressed. These tapes are absoultly the best possible reproductions of the dig tapes made from the masters (I only wish I had the actual reels so I could do a proper azimuth adjustment on them).



Sorry Chris,

I fail to see the relevance of this to the discussion. If you have a db x encoded tape you have to decode with db x. Why anybody would record to dat and have the resulting quality loss caused by the digitisation process and then decode bewilders me, surely working from the original analogue tape is way better, that's certainly my preferred option, even if we have to bake the tape.

The notes are correct in stating that signal levels were absolutely critical with db x, however even if you were bang on, in many cases you could/can still hear the "breathing" and with recording engineers who were used to turning up the wick, with db x you were on a hiding to nothing with this inflexible technology. The fact that studios like Abbey Road, Decca and the BBC, where engineers were expected to keep the level down and not distort, did not adopt db x speaks volumes. It was and still is rubbish technology in comparison to both the alternative ie Dolby and in fact, it was inferior to using no N/R at all.

[Light Dependant Resistor]

Here is a interesting article about Vangelis and his London Nemo studio. It reveals he as the artist and composer also tailored the sound he wanted. http://www.nemostudios.co.uk/nemo/tour/recording/recording_br.htm

[Lodgesound]

I have all 3 systems - DBX ( for reverse compatibility ) and Dolby A / SR in my studio for use in mastering - Dolby A wipes the floor with DBX and Dolby SR wipes the floor with Dolby A...

[PaulStewart]

I have all 3 systems - DBX ( for reverse compatibility ) and Dolby A / SR in my studio for use in mastering - Dolby A wipes the floor with DBX and Dolby SR wipes the floor with Dolby A...

+1 to the first bit and +1 to the second bit so a total of +2 to that :lol:

As for the interesting article about Vangelis and his London Nemo studio to quote the piece.....

"On the other hand, dbx noise reduction remained in use for the Lyrec TR-532 multitrack tape machine, but it proved to be a tricky system to use. As Nemo Studios was the only professional recording studio in London with dbx, repairs were difficult to arrange. It also meant that if Vangelis ever needed to go to another studio in Paris, New York or Los Angeles, logistics became a problem, as there were no other studios that used the dbx system, as they all used Dolby systems".

The reason for this is dbx N/R is pants and if I'm hionest Chris if your LDR passive pres really to exhibit companding asyou state in the original post. I would not go near them with a barge pole. For me the purpose of a high fidelity system is to remain faithful to the original signal. The clue is in the term high fidelity FFS. I'd give it a rest if I were you, you've dug a big enough hole, time to stop before you reach London :lol:

[Ali Tait]

Interesting thread here with some LDR measurements-

http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=5720&highlight=ldr

[PaulStewart]

Yes Ali I've seen that. I'm sorry for the thread drift as this thread is about mastering, it's just the OP mentioned LDRs in his first post, while trying to sell us on the idea that a dead and buried technology that was crap when new, is a good way to master. Don't get me wrong LDRs have their place, I use an optical compressor a la Joe Meek if I want that Tornados/Telstar suck and blow compression on a track, but that's all there any good for in audio in my opinion, no place in a HiFi set up.

[Ali Tait]

Well measurements aside, the LDR pre sounded very good in my system.

[SPS]

Well measurements aside, the LDR pre sounded very good in my system.

But not in mine Ali, myself and scott were not impressed at all..?

[Ali Tait]

Sounded very good at Owston too, as many agreed..

[awkwardbydesign]

Well measurements aside, the LDR pre sounded very good in my system.


But not in mine Ali, myself and scott were not impressed at all..?


Sounded very good at Owston too, as many agreed..

System dependent, like other passive pres? I like mine, but then I'm not exactly "high end"!

[Ali Tait]

Yes, like most stuff, system dependent. As Nick commented though, you may like the sound, but this pre isn't linear.

[SPS]

System dependent, like other passive pres? I like mine, but then I'm not exactly "high end"!

Yes but they are are not passive, they both add and taketh in unusual ways... The effect on the music was easy to hear... very unlike a normal passive vs powered pre comparision in my view

[awkwardbydesign]

Yes but they are are not passive, they both add and taketh in unusual ways... The effect on the music was easy to hear... very unlike a normal passive vs powered pre comparision in my view
What's a "normal" passive? TVC? Resistors?

[SPS]

Thats a fair point....

Resistive it what i was refering to..
Cheers

[awkwardbydesign]

Thats a fair point....

Resistive it what i was refering to..
Cheers
Ah. I am used to a TVC, not resistive. And they all have a varying output impedance, don't they? And my TVC had a +6db option (which I bypassed when I went to passive speakers, as I no longer needed the gain).
The one thing I have found with my passive pres (inc LDR) is the very low noise floor, which makes late night listening easier. But that's nothing to do with companders, though, AFAIK!

[Stratmangler]

Yes and a lot of other recordings from that time :( just had a listen to Katy Lied and yes you can still hear it breathing away. From a technical point of view, it's just not fast enough to be inaudible, the only one that did work(ish) was NICAM and that had other problems of it's own.

It's a real shame that Katy Lied came out the way it did - there's a subdued sound throughout, caused in no small part by the dBx units utilised during the recording and mixdown.
The material on the album is killer, and had it not been recorded with dBx it would have been regarded as a landmark album.
The album is still chock full of great performances!

[Audio Advent]

Ah. I am used to a TVC, not resistive. And they all have a varying output impedance, don't they? And my TVC had a +6db option (which I bypassed when I went to passive speakers, as I no longer needed the gain).
The one thing I have found with my passive pres (inc LDR) is the very low noise floor, which makes late night listening easier. But that's nothing to do with companders, though, AFAIK!

Looking at the graphs in that link above, it looked like the LDR thing was doing some odd things by increasing the levels of some of the testing rig distortion whilst reducing the level of the main signal - the distortion harmonics look like they increase for some attenuation levels. Maybe that's why companders and LDRs are being mentioned in the same thread, although looks more like just a compressor without the expander part.

Mild compression will be increasing the low level detail, making it more prominent and therefore could easily be interpretted as "more detail" or that the detail can be heard due to less noise, more "transparent". Not saying that is a feature of LDR passives as I've no idea if that one person's LDR passive test and results are valid or not. Something we all have to be aware of when assessing the sonics of any bit of equipment I guess! Is it really more detailed or is there mild compression? Nothing necessarily wrong with compression if the music then gives the listener more pleasure - that's what I say anyway - just not compatable with many audiophile's ideologies of playback systems.

[Light Dependant Resistor]

It's a real shame that Katy Lied came out the way it did - there's a subdued sound throughout, caused in no small part by the dBx units utilised during the recording and mixdown.
The material on the album is killer, and had it not been recorded with dBx it would have been regarded as a landmark album.
The album is still chock full of great performances!

Its hard to know what buttons were or were not pushed in 1975, but my guess is it was not the fault of the equipment rather how it was used and they have blamed DBX ever since for the mistakes they made.
This starts to sound likely as the DBX gear was newly installed. Possibly they were trying to expand the sound prior to going on tape and then re expand on playback. Readers would know as comparison who are used to tape decks failing to press Dolby B when recording, then going on to play back with Dolby it would not sound right.

Whether there is an audience still for Steely Dan is hard to say, but given they also had a Dolby tape as well and didn't want to remix it, says there is more to this story than we are being told, and will probably never hear.

Given many really good re mastering pieces of equipment exist today, one might start by having adequate hold time and digitally increase the release time in effect compensate for prior error.

[hifimerlin]

I am a new member, and forums are new to me. I would like to inform you of my experience with the DBX 150X unit, which I have had in my system for the past 2-3 years. I have been a friend of Chris for the past 20 years, we have built systems together, and are both passionate about good sound. We have listening sessions, and compare components which have had modifications done to them ( by Chris). I am no sound engineer, and have no great education on audio, but I feel I have a good ear for what is an improvement and what is rubbish.
When Chris came to me about 3 years ago, and told me of this improvement he was looking at, I was sceptical and did not believe that placing of an ageing DBX 150X in the signal path between the CD player and the preamp could actually improve the sound. We set up a listening session at my house and I was amazed with the improvement. The improvements were in soundstage, bass, definition, it really sounds a shit load better. The sound is not coloured in any way at all, it is natural and improved. I have always preferred the quality audio of record over cd, and with the addition of the DBX into the system, the frequency range sounds to be improved comparable to record. I know a lot will say that is rubbish, that is what I said before listening. All I ask is to try it, PS I do not own Shares in DBX :)
There was a time when I had the DBX unit was out of my system, during that time I really looked forward to having it back in the system, as the system lacked life. I now have a supply of DBX 150X's as they really are that good, just try one in your system you will be pleasantly surprised. It is low cost improvement for a big Gain. People run out and spend thousands on improvements, buying interconnects etc. I have bought some of my DBX's for less than $50.

[Audio Advent]

Whilst not a compander, I might try putting my compressor between pre and power on a low setting to see what happens for a subjective assessment. I'm a purist though and so will remove it after regardless of a positive effect (I'll leave the compression to the mastering or recording process). Of course many will also say how much better over-compressed CD sounds on their equipment, hence the "Loudness Wars" has had some sucess, whilst being demonised by audiophiles (rightly in my opinion) - they wouldn't use it if it didn't have a benefit in some area for some music.

[awkwardbydesign]

Looking at the graphs in that link above, it looked like the LDR thing was doing some odd things by increasing the levels of some of the testing rig distortion whilst reducing the level of the main signal - the distortion harmonics look like they increase for some attenuation levels. Maybe that's why companders and LDRs are being mentioned in the same thread, although looks more like just a compressor without the expander part.

Mild compression will be increasing the low level detail, making it more prominent and therefore could easily be interpretted as "more detail" or that the detail can be heard due to less noise, more "transparent". Not saying that is a feature of LDR passives as I've no idea if that one person's LDR passive test and results are valid or not. Something we all have to be aware of when assessing the sonics of any bit of equipment I guess! Is it really more detailed or is there mild compression? Nothing necessarily wrong with compression if the music then gives the listener more pleasure - that's what I say anyway - just not compatable with many audiophile's ideologies of playback systems.

Would the TVC compress? That had even better low level performance.
EDIT:
Just re-read the Audio Talk thread. I read it a while back, but hadn't had experience of the LDR pre then. Chris send has sent me an updated control board, and when I have got used to the new iteration I will try putting the TVC back in. I have to confess that although I appreciate the value of measurements, I am not clever enough to understand most of them!

[lurcher]

Looking at the graphs in that link above, it looked like the LDR thing was doing some odd things by increasing the levels of some of the testing rig distortion whilst reducing the level of the main signal - the distortion harmonics look like they increase for some attenuation levels.

Well, with respect, thats just a complex way of saying its non linear. gain is not equal for all signal levels. The distortion terms of the test rig itself put 2nd at -105dB and 3rd at -100dB. The equivalent input and 20dB attenuation for a resistive attenuator put all the distortion products below the noise floor.

[Macca]

Its hard to know what buttons were or were not pushed in 1975, but my guess is it was not the fault of the equipment rather how it was used and they have blamed DBX ever since for the mistakes they made.
This starts to sound likely as the DBX gear was newly installed. Possibly they were trying to expand the sound prior to going on tape and then re expand on playback. Readers would know as comparison who are used to tape decks failing to press Dolby B when recording, then going on to play back with Dolby it would not sound right.

Whether there is an audience still for Steely Dan is hard to say, but given they also had a Dolby tape as well and didn't want to remix it, says there is more to this story than we are being told, and will probably never hear.

.

They blamed the studio but as you say the full story will probably never be told. They did take the tapes to the DBX factory in Boston and they had a fiddle with them but could not recover the sound.

I suppose using DBX to play back existing recordings is not the same as actually recording with it. Like anything in this game it's wise not to knock it until you've tried it.

Is there still an audience for Steely Dan? Err.....yes. Yes there is.

[Stratmangler]

Is there still an audience for Steely Dan? Err.....yes. Yes there is.

I've been in the Steely Dan audience for nearly 40 years.

With regard to the problems with the recording of Katy Lied http://www.steelydan.com/dennys3.html

[Lodgesound]

I am a new member, and forums are new to me. I would like to inform you of my experience with the DBX 150X unit, which I have had in my system for the past 2-3 years. I have been a friend of Chris for the past 20 years, we have built systems together, and are both passionate about good sound. We have listening sessions, and compare components which have had modifications done to them ( by Chris). I am no sound engineer, and have no great education on audio, but I feel I have a good ear for what is an improvement and what is rubbish.
When Chris came to me about 3 years ago, and told me of this improvement he was looking at, I was sceptical and did not believe that placing of an ageing DBX 150X in the signal path between the CD player and the preamp could actually improve the sound. We set up a listening session at my house and I was amazed with the improvement. The improvements were in soundstage, bass, definition, it really sounds a shit load better. The sound is not coloured in any way at all, it is natural and improved. I have always preferred the quality audio of record over cd, and with the addition of the DBX into the system, the frequency range sounds to be improved comparable to record. I know a lot will say that is rubbish, that is what I said before listening. All I ask is to try it, PS I do not own Shares in DBX :)
There was a time when I had the DBX unit was out of my system, during that time I really looked forward to having it back in the system, as the system lacked life. I now have a supply of DBX 150X's as they really are that good, just try one in your system you will be pleasantly surprised. It is low cost improvement for a big Gain. People run out and spend thousands on improvements, buying interconnects etc. I have bought some of my DBX's for less than $50.

Hi there;

I find your experience interesting most noteably as you are using a compander for single-ended operation ie. you are "decoding" recordings that have not been encoded in the first place.

I am amazed that the artifacts that this process will generate do not adversely affect your listening experience.

[PaulStewart]

Hi there;

I find your experience interesting most noteably as you are using a compander for single-ended operation ie. you are "decoding" recordings that have not been encoded in the first place.

I am amazed that the artifacts that this process will generate do not adversely affect your listening experience.

+1 Single ended expansion will be as far from "High Fidelity" as one can get IMO. I did use a dbx expander in this mode once however in the mid 80s I was a senior sound tech at Theatre Sound and Light. When West Side Story returned to the Her Majesty'sTheatre in Haymarket the director needed a sound effect to magnify the sound of a door slamming we used a contact mic into the desk then into the expander and out to the PA. We used this system precisely because it would exaggerate the slam un-naturally . Worked a treat but play music back through it, err Nah! :laugh:

[Light Dependant Resistor]

+1 Single ended expansion will be as far from "High Fidelity" as one can get IMO. I did use a dbx expander in this mode once however in the mid 80s I was a senior sound tech at Theatre Sound and Light. When West Side Story returned to the Her Majesty'sTheatre in Haymarket the director needed a sound effect to magnify the sound of a door slamming we used a contact mic into the desk then into the expander and out to the PA. We used this system precisely because it would exaggerate the slam un-naturally . Worked a treat but play music back through it, err Nah! :laugh:

No, the 150x Jamie describes is being used real time, as explained in post 1, and on page 9 of the 150x manual.http://dbxpro.com/en/products/150x
Cabling is shown in this image: 13709

To quote the manual " Each channels encoder and decoder can be used independently at the same time, so full decoded monitoring is possible....... This dynamic range exceeds 16 bit PCM system and all other analog noise reduction systems even the new Dolby SR compander ".

So connecting up you also need to refer to Page 8 of the 150x manual , where because the 150x can be used with balanced or unbalanced equipment care needs to be taken with outputs with unbal equipment that a stereo phone plug is used and the ring is unconnected. Connections are 8 phone jacks ( *observing unbal use outputs are stereo type ring unconnected ) From source typically a CD player this is Console in L and R, Tape Out* is linked L out to Left tape In and R Tape Out* is linked to Right Tape In. Finally Left Console Out*, connects to Left of your pre amps line level input and same for Right Out *

Whilst using a 150x real time, is very good it can also be used with a recording device like a yamaha CDRHD1500 if like me you do not like CD's and their covers where Console In comes from a CD player or other source, Tape Out feeds the input of the Yamaha for recording, the output on playback of the Yamaha feeds tape In of the 150x and the Console Out feeds the stereo coffee ldr attenuator.

Cheers / Chris

[Lodgesound]

I underdstand your process chain now.

What you are doing effectively is companding the audio signal (encoding then decoding) simultaneously with no tape machine in the chain.

A similar process can be applied by linking 2 Dolby units (A or SR) together with one unit switched to encode and the other switched to decode.

The theory is quite sound and indeed does add a certain "warmth". Experiments were even done using such chains when mastering DAT tapes believe it or not.

The problem with such a system lies with what DBX and Dolby were both designed to reduce in the first place - analogue tape noise floors.

By using such a chain on what is basically a very low noise floor source (in theory system noise in a well setup analogue system being fed with a high quality digital source) this "floor" at the start can be as low as around -78 dB.

If you apply this into such a compander network the system acts on the residual noise floor which results in unnatural processing of very low level signals. These low level signals in a high quality recording done on machinery with a very low inherent noise floor - much lower than that of analogue magnetic tape - will be seated perfectly within the range and capability of that system.

If you then apply a companding network this balance is offset and whilst the initial effect one hears is extremely warm and punchy sounding subleties at low levels within the recording become severely distorted and in some cases almost eliminated.

If one introduces an analogue tape recorder into the chain and applies the same process what you end up with is a well balanced extremely low noise high quality recording which can exhibit much of the allure that analogue mastering used to provide in days gone by.

In short both DBX and Dolby units need real tape noise to work correctly within their respective design parameters.

[PaulStewart]

Chris I'm sure you're a nice bloke, but this is all nonsense you can't reduce noise that is already there and if you synthesise dynamic range it is just artifact not real. When you compress in mastering the compressed signal is what the creators ie musicians, producers and engineers expect you to hear. If you add false dynamic range it's not hi fi end of story. Sorry but I'm out of this thread the whole premise is total nonsense.

[Audio Advent]

It might not be hifi but some people might prefer the sound.. I guess that's up to them.

I only know the basics of studio stuff but remember the feeling of wanting an expander after reading about a good one in sound on sound (TC electronics 1210 sounds about right after a quick google - http://www.soundonsound.com/sos/1997_articles/feb97/tcelectronic1210.html ) to make everything sound good; depth, richness (copying that from the above article). Then people love the sound and want to put it on everything they mix..

Same would be the case with just playback n'est pas?

I'm a purist at heart these days and so wouldn't do that kind of thing as I think it's better to find natural richness and depth by better mics, mic pres or simply technique. Wouldn't do it to my playback system either.. well could put it on a tape loop to switch in and out just when I want something more comforting, like indulging yourself in whatever floats your boat; ice-cream, sitting watching rom-coms wrapped in a duvet etc. But then there comes a point where everything sounds the same and you want reality back!

[Audio Advent]

Well, with respect, thats just a complex way of saying its non linear. gain is not equal for all signal levels. The distortion terms of the test rig itself put 2nd at -105dB and 3rd at -100dB. The equivalent input and 20dB attenuation for a resistive attenuator put all the distortion products below the noise floor.

There's no need for the respect! :D I'm never sure what is meant by non-linear, whether it's about non-linear regarding freqency or amplitude (everything attenuated by a percentage of their level rather than a fixed dB amount). Hard to say with those graphs which is happening. Hence the long-winded description.

[lurcher]

With respect to amplitude. The frequency response was nice and flat. The added harmonics was the result of a non linear (amplitude) transfer function.

[Light Dependant Resistor]

It might not be hifi but some people might prefer the sound.. I guess that's up to them.

I only know the basics of studio stuff but remember the feeling of wanting an expander after reading about a good one in sound on sound (TC electronics 1210 sounds about right after a quick google - http://www.soundonsound.com/sos/1997_articles/feb97/tcelectronic1210.html ) to make everything sound good; depth, richness (copying that from the above article). Then people love the sound and want to put it on everything they mix..

Same would be the case with just playback n'est pas?

I'm a purist at heart these days and so wouldn't do that kind of thing as I think it's better to find natural richness and depth by better mics, mic pres or simply technique. Wouldn't do it to my playback system either.. well could put it on a tape loop to switch in and out just when I want something more comforting, like indulging yourself in whatever floats your boat; ice-cream, sitting watching rom-coms wrapped in a duvet etc. But then there comes a point where everything sounds the same and you want reality back!

Companding whether it be Dolby or DBX are both methods to capture the original sound on mediums that in the case of tape cannot possibly fit the dynamics that the source material is providing.
If you choose not to use any form of companding with analog methods then very good tape and fast speed is required. It is healthy to view the recorder as a medium of loss, not of capture
and to minimize that loss where ever possible.

In the case of digital recording companding may be helpful to lessen the restriction imposed by -7db attenuation. In both cases on the other side of the door patiently waiting is noise.

In the case of using a type 1 DBX, DBX DDP Quantum or Dolby A ( I do have one of these ) or Dolby SR in your audio system. Type 1 DBX is by far the least expensive to try as it
provides full decoded monitoring without a recording medium . It is quite apparent (and I think I can unanimously speak for two other friends who are yet to contribute to this forum)
that it effortlessly improves CD playback without taking anything away . As Jamie simply said, try it.

Cheers / Chris

[Audio Advent]

If you're worried about the -7db level standard wouldn't you therefore have to apply compression before digitisation and then expanding after the d/a? Applying companding with no process in between should, in a perfect world, be absolutely transparent. That it makes a difference means that the process being used is not perfect and what you are hearing is the effects of the non-perfect application changing the signal. Or indeed it is only supposed to be perfectly transparent when used in conjuction with tape and without that tape in between, there is a mis-match between the compression and expansion. (I'm purposely disregarding the opinions of the "breathing" etc - never heard one myself).

The review of the TC Electonics 1210 expander says how it makes everything sound richer and gives more depth - this is an effect. The reviewer then says how thin and lacking his final stereo mixes sound in comparison if he doesn't use it and so uses it on everything. Compression alone will also make the source sound more dynamic, again an effect.

If effect boxes make your system sound better to your ears then people should feel free to adjust their system to suit their own tastes. It does go against most audiophile's philosophies though - and some audiophiles get around that philosophy by choosing audiophile equipment which colours the sound to their tastes instead whilst insisting they are purists too..

But hey, that's the caveat of working subjectively - you never know whether something sounds more real or realistic because of some un-natural effect of the equipment rather than being absolutely true to the source. But better to be subjective and get that bit wrong in my opinon than stick with ultra-objectivity and insist that a boring sound is "correct" .
With digital though, isn't the answer simply to use higher bit rates so that the dynamic range is higher? Even with -7dB on 44.1/16, the dynamic range available is theoretically higher than any analogue medium. Add recording at higher than 20bits and the right noiseshaping/dithering, and a DAC of 20+bits then you can achieve about 120dB of perceived dynamic range on a 16-bit medium and the -7db part becomes even less of an issue if it ever was one in the first place. 20bit A/D has been the equipment standard for the last 20 years or so. Have you ever tried adding something like the Meridian 518 digital processor between transport and DAC? You can apply noise-shaping dither on the fly whilst re-sampling up to 24 bit for replay on a 24bit dac. Maybe it will improve things too?

[Light Dependant Resistor]

If you're worried about the -7db level standard wouldn't you therefore have to apply compression before digitisation and then expanding after the d/a? Applying companding with no process in between should, in a perfect world, be absolutely transparent. That it makes a difference means that the process being used is not perfect and what you are hearing is the effects of the non-perfect application changing the signal. Or indeed it is only supposed to be perfectly transparent when used in conjuction with tape and without that tape in between, there is a mis-match between the compression and expansion. (I'm purposely disregarding the opinions of the "breathing" etc - never heard one myself).

The review of the TC Electonics 1210 expander says how it makes everything sound richer and gives more depth - this is an effect. The reviewer then says how thin and lacking his final stereo mixes sound in comparison if he doesn't use it and so uses it on everything. Compression alone will also make the source sound more dynamic, again an effect.

If effect boxes make your system sound better to your ears then people should feel free to adjust their system to suit their own tastes. It does go against most audiophile's philosophies though - and some audiophiles get around that philosophy by choosing audiophile equipment which colours the sound to their tastes instead whilst insisting they are purists too..

But hey, that's the caveat of working subjectively - you never know whether something sounds more real or realistic because of some un-natural effect of the equipment rather than being absolutely true to the source. But better to be subjective and get that bit wrong in my opinon than stick with ultra-objectivity and insist that a boring sound is "correct" .
With digital though, isn't the answer simply to use higher bit rates so that the dynamic range is higher? Even with -7dB on 44.1/16, the dynamic range available is theoretically higher than any analogue medium. Add recording at higher than 20bits and the right noiseshaping/dithering, and a DAC of 20+bits then you can achieve about 120dB of perceived dynamic range on a 16-bit medium and the -7db part becomes even less of an issue if it ever was one in the first place. 20bit A/D has been the equipment standard for the last 20 years or so. Have you ever tried adding something like the Meridian 518 digital processor between transport and DAC? You can apply noise-shaping dither on the fly whilst re-sampling up to 24 bit for replay on a 24bit dac. Maybe it will improve things too?

Well written, yes higher bit rates and doing very clever things described in DBX's white paper on their Type 4 noise reduction, that gives recognition to Type 1 . ftp://ftp.dbxpro.com/pub/pdfs/WhitePapers/Type%20IV.pdf
Basically when sound starts to get so accurate that musicians instruments or voices are life like is where one scrambles for a computer or piece of paper to write down how it is achieved is where I head.

The purpose of this thread is to open audiophiles appreciation of recording and mastering sound, discuss some of the many products that do it, and invite some of those techniques to be more commonplace in audio systems shared used and commented upon. It would be lovely to come back here in a few months and find .. I had really good experience with a Dolby or a DBX. Paul has already let us know Dolby SR has nice result, so where can one find a Dolby SR ?
.
Also to hear of amazing recordings that did not use companding. This morning I was reading some of the craft of Prof Keith O Johnson, and his use of a 3Mhz bias into a recording head http://www.goodwinshighend.com/library/keith_johnson.htm as I have and appreciate the Michael Garson recording Serendipity

Upstairs at the moment I am doing a comparison of Type 1 DBX vs DBX quantum with a Yamaha hard disk CDRHD1500 as the medium holding both, The Quantum I have programmed to compress, given it about 50msec of
Transient Capture Mode and set hold and release, then settings on Program 2 to expand, through this exercise I am trying to learn what are the better settings for companding by looking at each characteristic.
I am yet to find better settings than in the 150x, but I am sure they are there. At this rate I will have to dust off the Dolby A :) which I also know has very good sound.

Cheers / Chris

[Lodgesound]

Can I ask - do you own a professional open reel analogue recorder (by that I mean a studio machine) and also wondered which type of studio monitor speakers you are running (ATC's, Tannoys, JBL's, Urei etc..).

To get benefit from DBX, Dolby SR or A you must use an analogue tape mastering stage - that is what these systems are for - to reduce (not eliminate) analogue tape noise floors.

As has been stated by Paul you cannot remove or reduce noise that was present at the point of the original recording.

I would be interested to know your tape formulations along with bias/eq settings on your studio machine.

[Light Dependant Resistor]

Hi Stewart
The 150x specifies that it may be used for linear transmission media with 20hz-20khz +-1db response, whilst this principally means 15ips tape,

DBX go on to say " Some recordists may wish to investigate using their 150x with a 16 bit or a 14 bit PCM digital recorder. In effect the 150x will adequately dither ( Dither is routinely used in processing of both digital audio and digital video data, and is often one of the last analog stages of audio production to compact disc ) such a machine, as well as increase its usable dynamic range some 20db, and thereby change any digital sound its noise floor has
In such a combination there will be no mistracking and no possibility of audible noise modulation"

I use a Yamaha CDRHD1500 which is a 44.1 Khz 16bit recorder, and speakers are Quad ESL57 stacked driven by 2x Quad 306 , alternatively I use Gale GS401a or JR149, and AKG701 headphones.

The use of a 150x without a recorder being connected for full decoded monitoring by this advice DBX provide is correcting digital sound noise floor, no wonder it sounds so good !

Cheers / Chris

[PaulStewart]

The use of a 150x without a recorder being connected for full decoded monitoring by this advice DBX provide is correcting digital sound noise floor, no wonder it sounds so good !

Cheers / Chris

:laugh: :laugh: :laugh:

Chris, we tried this years ago at JVC and it simply does not work, it may sound punchy, but it breathes and masks low end detail.

[SPS]

:laugh: :laugh: :laugh:

Chris, we tried this years ago at JVC and it simply does not work, it may sound punchy, but it breathes and masks low end detail.

That describes the Ldr preamp nicely too, when i tried one

[Light Dependant Resistor]

Hi Paul
But when you were at JVC working on Super ANRS was this 1976 ? a Type 1 DBX 150x had not even been designed, its design years being between 1979 and 1986

JVC's super ANRS was a system designed for cassette and as I gather trying to better Dolby B but introduced a lot of incompatibility for end users. It was not compatible with any DBX product.

Adding this up Paul's suggestion of Dolby SR is worthwhile hearing, There is a lot of misinformation about DBX products particularly Type 1, and some voicing opinions without even hearing it, basing those opinions
strangely on products that were not made by DBX. Yet others who have heard Type 1 DBX , greatly appreciate what it does, Is that a fair summary ?

Cheers / Chris

[PaulStewart]

We were constanyly looking at both our own kit and other peoples, as was every other manufacturer, this was around 79!or perhaps 1980 when we did this. I had DBX in the studio I set up on the Rainbow theatre in 81. IIRC and certainly we had cards for the Dolby rack at Village Way recorders in 82 (the ones we slung in the cupboard).

As Steve (SPS) says above this also describes what LDR pres do to the sound in my opinion, now I know some people like this form of presentation, but it's neither natural or neutral and is about as far as one can get from the ideal "straight eire with gain" that HiFi is about. FWIW, I never speak from a point of view of commenting unless I've had direct experience of something. After around 50 years of experience of playing around with dound kit, most of these as a professional, I know that a linear approach to sound reproduction, is the right one.

[Light Dependant Resistor]

We were constanyly looking at both our own kit and other peoples, as was every other manufacturer, this was around 79!or perhaps 1980 when we did this. I had DBX in the studio I set up on the Rainbow theatre in 81. IIRC and certainly we had cards for the Dolby rack at Village Way recorders in 82 (the ones we slung in the cupboard).

As Steve (SPS) says above this also describes what LDR pres do to the sound in my opinion, now I know some people like this form of presentation, but it's neither natural or neutral and is about as far as one can get from the ideal "straight eire with gain" that HiFi is about. FWIW, I never speak from a point of view of commenting unless I've had direct experience of something. After around 50 years of experience of playing around with dound kit, most of these as a professional, I know that a linear approach to sound reproduction, is the right one.

Hi Paul
I think Steve's comments were vague and crude to say the least, he did not inform which LDR preamp he had heard. More is the point, I am still unclear if despite your assertion of commenting when you have direct experience that on this occasion you are just relying on Steve's assessment and not your own. So tables up, have your heard a good LDR pre ? and have you heard what a DBX 150x does in a domestic audio system, no hiding under the table guessing and no I don't want to please, just a straight NO i have not heard either, or Yes i have heard both, which is it ?

Cheers / Chris

[SPS]

Yes i suppose my comments were crude, my appologies, but it was not crude in the way it was done by myself and scott lyngren aka scottmoose, a well known and respected speaker designer, with better ears than me in my view

My system is an extremely revealing. its used the best amplifing devices i know, uses high quality interstage and output transformers, (tribute), and i would say is close to reproducing accurately
I make a point of trying out and listening to other gear , and if i know of another type of set up that was better i would be using it... Within reason cost wise
The speakers are open baffles using beyma amt, fostex tweeters, vitavox and fane mid/ bass drivers1x12/15/18 per side around 102 dbs,
At the last wigwam show quite a few who visited my room commented that it was like the singer was in the room. My speakers have been substantially updated since then

The LDR was the one that did the rounds via mark achman, and was the one nick measured,

It was plugged in to warm up for a while before it was tested, it used in directly between a 16 chip terradac, which is in my view very clean and transparent, and my px25 amp.

After a hours listening that night i swapped the LDR in, the leading edges to the transients where clearly muffled, taking away the life to the sound , it was easily noticable to us both, there was also an unusual effect on the sound of the music a brightening effect, it muffled the music but gave the music an artificial edge .. Its difficult to describe but it was a subutle but real difference. It left me feeling that the music was confused, it was unusual.

After 3-4 tracks ( tracks that we had played just before ) scott could stand it no longer , its was taken out of the system.
I normally use stepped attenuators but this amp has a panasonic pot in the grid leak position, it was turned to full volume to provide a 'straight through ' route for the signal
We have no measurements but we both discribed the same effects on the music being reproduced.

I would also be happy for any one to bring one to the next wigwam show and i would gladly demonstrate.
Thanks..
Steve shiels

[Light Dependant Resistor]

Yes i suppose my comments was crude, but it was not crude as it was done.
Myself and scott lyngren aka scottmoose, a well known and respected speaker designer, with better ears than me in my view

My system is an extremely revealing. its used the best amplifing devices i know, uses high quality interstage and output transformers, (tribute), and i would say is close to reproducing accurately
I make o point of trying and listening to other gear , and if i know of another type of set up that was better i would be using it.
The speakers are open baffles using beyma amt, fostex tweeters, vitavox and fane mid/ bass drivers1x12/15/18 per side around 102 dbs,
At the last wigwam show quite a few who visited my room commented that it was like the singer was in the room. My speakers have been substantially updated since then

The LDR was the one that did the rounds via mark achman, and was the one nick measured,

It was plugged in to warm up for a while before it was tested, it used in directly between a 16 chip terradac, which is in my view very clean and transparent, and my px25 amp.

After a hours listening that night i swapped the LDR in, the leading edges to the transients where clearly muffled, taking away the life to the sound , it was easily noticable to us both, there was also an unusual effect on the sound of the music a brightening effect, it muffled the music but gave the music an artificial edge .. Its difficult to describe but it was a subutle but real difference. It left me feeling that the music was confused, it was unusual.

After 3-4 tracks ( tracks that we had played just before ) scott could stand it no longer , its was taken out of the system.
I normally us stepped attenuators but this amp has a panasonic pot in the grid leak position, it was turned to full volume to provide a 'straight through ' route for the signal
We have no measurements but we both discribed the same effects on the music being reproduced.

I would also be happy for any one to bring one to the next wigwam show and i would gladly demonstrate.
Thanks..
Steve shiels

Hi Steve
Apologies accepted , Thanks for your assessment, the setup of using another pot even though straight through is not ideal, even coupling LDR's in series let alone a conventional pot following is a big no no to how they should be connected. I know quite a few members on AOS and on audio talk forums have had lots of pleasant listening with the loaner when it is connected as intended. So to have a sound that you described as muffled is not what it does.

I would be glad to send you a built kit ( and a 150x ) so you can properly assess what we are hearing here and in Australia. for the purpose of the Wigwam show.

Cheers / Chris

[PaulStewart]

Oh FFS Chris, forgive me but I was using this kit, probably before you were a twinkle in your daddys eye. I built LDR circuits in the 60s when I was a kid. They make great "suck and blow" compressors and lousy pre amps, see Steve's comments above, with which I concour. I have, while working on a passive pre project for a client, tried LDRs and concluded that a good stepped attenuator was better. I heard at that time a couple of commercially available units too. I have heard dbx type 1 (not perhaps 150x) and other compandres used in domestic audio systems and I have heard dbx type 1 used in studios in both similtaneous monitoring and on tape replay. In EVERY case, they reproduction was better without these units than it was with them.

[SPS]

I am a little confused, as i thought with just a 100k resistor on the grid made the amp in to the eqiverlent of a power amp, if that makes sense, or at least the same configeration as a standard power amp

I use the pot in place of the grid leak, so there is only one input to ground connection, not in addition to it

Im more than happy to assess your kit.. If you really want me to,
but i know it can make some systems the impression of a better sound.
it may be better suited to those systems
Steve


Hi Steve
Apologies accepted , Thanks for your assessment, the setup of using another pot even though straight through is not ideal, even coupling LDR's in series let alone a conventional pot following is a big no no to how they should be connected. I know quite a few members on AOS and on audio talk forums have had lots of pleasant listening with the loaner when it is connected as intended. So to have a sound that you described as muffled is not what it does.

I would be glad to send you a built kit ( and a 150x ) so you can properly assess what we are hearing here and in Australia. for the purpose of the Wigwam show.

Cheers / Chris

[Audio Advent]

DBX go on to say " Some recordists may wish to investigate using their 150x with a 16 bit or a 14 bit PCM digital recorder. In effect the 150x will adequately dither ( Dither is routinely used in processing of both digital audio and digital video data, and is often one of the last analog stages of audio production to compact disc ) such a machine, as well as increase its usable dynamic range some 20db, and thereby change any digital sound its noise floor has
In such a combination there will be no mistracking and no possibility of audible noise modulation"

I use a Yamaha CDRHD1500 which is a 44.1 Khz 16bit recorder, and speakers are Quad ESL57 stacked driven by 2x Quad 306 , alternatively I use Gale GS401a or JR149, and AKG701 headphones.

The use of a 150x without a recorder being connected for full decoded monitoring by this advice DBX provide is correcting digital sound noise floor, no wonder it sounds so good !

Cheers / Chris

Do they mean "home recordists" in that snipet, and the idea of using encoding before and decoding after the recording just as you would with tape?

The early 90s brought studio quality digital dither boxes that were cheap enough to use in the home, e.g. Meridian's 618. In the studio world we also would have had UV22HR dither, HDCD as another kind of dynamic processing and JVC's K2 business. Nowadays you can get great noise-shaping dither algos as plug-ins and are standard on digital audio workstations, many digital products offer dithering, noise-shaping before output etc etc..

The beauty of most of all that (apart from HDCD) is that you don't need any special equipment for decoding on playback as it is all done in the ditigal domain, not the analogue domain. So unless you have some particular CDs produced without dither (any early CDs or probably a many before the mid-90s?) I don't see that there will be any dynamic/noise floor issues which could be solved by the dbx process as this has effectively already been carried out.

I can't help but feel you're enjoying the effects of compression or expansion rather than any noise-floor reduction. Try getting hold of a straight expander or compressor and try it out too.

[Light Dependant Resistor]

Do they mean "home recordists" in that snipet, and the idea of using encoding before and decoding after the recording just as you would with tape?

The early 90s brought studio quality digital dither boxes that were cheap enough to use in the home, e.g. Meridian's 618. In the studio world we also would have had UV22HR dither, HDCD as another kind of dynamic processing and JVC's K2 business. Nowadays you can get great noise-shaping dither algos as plug-ins and are standard on digital audio workstations, many digital products offer dithering, noise-shaping before output etc etc..

The beauty of most of all that (apart from HDCD) is that you don't need any special equipment for decoding on playback as it is all done in the ditigal domain, not the analogue domain. So unless you have some particular CDs produced without dither (any early CDs or probably a many before the mid-90s?) I don't see that there will be any dynamic/noise floor issues which could be solved by the dbx process as this has effectively already been carried out.

I can't help but feel you're enjoying the effects of compression or expansion rather than any noise-floor reduction. Try getting hold of a straight expander or compressor and try it out too.

Hi
The recommendation that DBX make is particularly for systems that have lower bit rate, and explained in terms of noise floor here: http://www.homestudiocorner.com/24-bit-vs-16-bit/
The use of outboard DACs that couple digital via SPDIF would appear to have cumulative noise from many sources see Chris Dunn. Malcolm Hawksford http://audioworkshop.org/downloads/AES_EBU_SPDIF_DIGITAL_INTERFACEaes93.pdf

My own exploration of this in 1996 brought good result from bypassing SPDIF altogether http://www.enjoythemusic.com/magazine/viewpoint/0401/deficienciesofspdif.htm

I recall the improvement with a good Digital to Analog converter Ultra analog D20400 using flip flops clocking at transmission of bitclock data and word upon transmission and reception, have similar attributes
in better stereo separation and bass reproduction, as a DBX 150x achieves. It is interesting to note the use of outboard word clocks using a BNC connector in mastering equipment, are providing the same advantage on one of the word lengths.

So recommending a DBX as an addition to digital based audio systems, would appear to be quite valid either from using lower bit CD players, or in systems with higher bit capability where cumulative noise from
outboard D/A conversion has raised noise level.

I am currently trying a DBX DDP and DBX Quantum to see if either as using them as psuedo noise reduction units ( compression during recording and expanding on playback ), can rival what the 150x does
presently the 150x is better.I am also carefully listening to standard replay without DBX

Cheers / Chris