Pre-amps are they worth it?

[Covenant]

For a couple of years I have used my Beresford Caiman as a pre-amp and been happy with what it does. Recently I have tried a couple of tube pre's and have not been overwhelmed by the difference. One was, admittedly a cheap Far East one but the other was worth about £400.
Obviously synergy comes into the equation but I would be interested to hear about pre's that have transformed a system, tube or solid state.

[julesd68]

Although only their "budget" pre, my Audio Note M-Zero certainly transformed my system. Just seems to have an amazing synergy with my 405-2. I tried three or four other pre's before giving this a go. The funny thing was that the dealer I bought it from did his best to talk me out of it - he didn't think the valve / solid-state combo would likely work! Gives me a much bigger soundstage with masses of grip and authority. The remote control is rather nice too .... :D

[Puffin]

Jerry, didn't I make you a Lightspeed....errr Lightspeed years ago?

I am still using the first one I ever made and I have to say that IMO it is the most transparent pre I have heard. I have used an Alps Blue passive pre, Valve Pre, Exposure Pre (very good, but one channel decided to die and I cannot be bothered to fix it!) Oh and an Audiolab 8000A as a pre.

My L/S is teamed with a Pass B1 buffer and I think that for the money (DIY of course) I would have to spend a lot of dosh to beat it.

I have tried my Modded Marantz CD63 straight into the power amps. Not bad, but a good pre seems to do the business

[hoopsontoast]

I would say there is a massive difference IME.
I went from a Big integrated (Sony TA-F670ES) to the 670ES running into ASL monoblocks (using the pre out) and there was a difference (as you would expect) but did not stand out.
I then got my LA3, and that into the ASL's was simply staggering. Soundstage/imaging to die for and better controlled bass, and generally 'bigger' sound. Really cant get over why I never tried a seperate pre amp before.
Obviously YMMV but I would say as long as your power amp can drive the speakers to the levels you need, then the biggest change you may hear will be in a better pre-amp.

[Covenant]

Jerry, didn't I make you a Lightspeed....errr Lightspeed years ago?

I am still using the first one I ever made and I have to say that IMO it is the most transparent pre I have heard. I have used an Alps Blue passive pre, Valve Pre, Exposure Pre (very good, but one channel decided to die and I cannot be bothered to fix it!) Oh and an Audiolab 8000A as a pre.

My L/S is teamed with a Pass B1 buffer and I think that for the money (DIY of course) I would have to spend a lot of dosh to beat it.

I have tried my Modded Marantz CD63 straight into the power amps. Not bad, but a good pre seems to do the business

You did indeed Rob. I will dig it out and try it again, this time with my Croft power amp. What does the Pass buffer add?

[hifinutt]

i have tried loads of pre amps in recent years , bel canto pre 3 , bel canto pre 3 vbs, mfa calssic silver mark 1 and mark 2, belles vt-01, vtl 5.5 , tom evans vibe /groove and currently the arc ref5se

certainly all of them were brilliant with notable exception being the mfa mark 2 which had incredible dynamics and transpency and the ref 5 has amazing holographics fra better than using a dac as pre

[Puffin]

You did indeed Rob. I will dig it out and try it again, this time with my Croft power amp. What does the Pass buffer add?

From the review by Enjoy The Music.

http://www.enjoythemusic.com/magazine/equipment/0708/first_watt_b1_preamplifier.htm

[1st Watt's latest DIY offering, the B1 buffer stage, is described by Nelson Pass as "a no-feedback JFET buffer that offers ultra low distortion and noise with ultra wide bandwidth." If you are unfamiliar with First Watt's product spectrum and with the underlying philosophy of its progenitor, Nelson Pass, I strongly suggest that you visit the First Watt website for an orientation. In a nutshell, Nelson believes that simple elegant designs are the most worthy of his time and your money.

The speed limit metaphor refers to the fact that the buffer has no voltage gain and thus the system's overall gain is limited to the gain of the front-end source component plus that of the power amp. Well, that brings up the question of just how much gain is needed? Obviously, a CD player with a nominal 2V line signal presents no problems at all for the buffer preamp. Most power amps feature an input sensitivity between 1 and 2 V, which mean that a typical CD player needs no additional gain in order to redline most power amps. But take a look at the line inputs on most line stages and preamplifiers. The signal is forced to undergo 12 to 18 dB or more of amplification. That's very likely a throwback to the days when line inputs were nominally 0.2 V (tuners and tape decks, for example), which require a gain of 1.5/0.2 (assuming a power amp sensitivity of 1.5 V) or a factor of 7.5. Now, that's about 18 dB of gain. I am certain that no CD player, whatever its pedigree, would sound its best when fed into a high-gain line-level input. Imagine the sonic indignity of first throwing away most of the signal at the volume control and then forcing it through an active gain stage to build it up again — hardly an optimal situation. [/I]

[electric beach]

My preamp experience is very limited, I've only ever had one and that's the lesser known Mapletree Audio Line 2A SE.
http://hollowstate.netfirms.com/#Preamplifiers

Without it, paired with either 35w KT88 P/P or 2.5w SET or Amptastic T-amp, I can get more transparency,detail and definition, tighter bass, more extended high frequencies and more punchy dynamics. :doh:

With it I invariably get a deep soundstage with tangible and realistic 3D impression of the performers and their instruments playing. I get instrument timbre. I get performance emotion and musical connection. :smoking:

[Butuz]

If your using the Caiman as a pre amp then there is plenty more good stuff to come on your hifi journey when you start trying out pre amps. The Caiman one is not bad at all - considering it comes free built in to the DAC.

Like Puffin I also use a DIY nelson pass B1 buffer only mine is an "as cheap as possible" design and only has a cheap alps blue pot for the volume. Put simply it monsters the £200 Caiman. It also monsters the pre amp built into my Quad CDP-2 CD player and that's a £1000 part new.

Here is a thread I made about my Pass B1: http://theartofsound.net/forum/showthread.php?t=19674

Butuz

[MartinT]

I would say a good preamp is essential and can define the structure of the system since it is so central to successful sound quality. The single most important attribute is its ability to properly drive the power amplifier. No passive system I've ever heard really lays on the foundations and dynamics the way a good preamp does.

I discovered preamps with my first one: a Pass Labs X2. Then I upgraded to an X1. Now I have an XP-20.

[Marco]

The single most important attribute is its ability to properly drive the power amplifier.

+1. Virtually all passive preamps I've heard make for a soft sound, lacking in drive and dynamics, compared with the best active designs. However, it can be different when a passive preamp and power amp have been designed to work together by the same manufacturer.

In any case, a good dedicated preamp is an essential addition to any top-notch system, but good ones often don't come cheap. Think in the region of £1000+, or buy a Croft! :)

Marco.

[Covenant]

As I have a Croft power amp the Micro is the obvious choice. However it's nice to try a few alternatives before settling with one of Glenn's offerings!

[StanleyB]

+1. Virtually all passive preamps I've heard make for a soft sound, lacking in drive and dynamics, compared with the best active designs. However, it can be different when a passive preamp and power amp have been designed to work together by the same manufacturer.

Same here. I use a passive preamp circuit in the TC-7520 and Caiman, but I have never been happy with the slight softness of the output.

[Covenant]

Same here. I use a passive preamp circuit in the TC-7520 and Caiman, but I have never been happy with the slight softness of the output.

At least it doesn't cause the Croft fuse to blow which is what seems to happen with most preamps I have tried. :(

[StanleyB]

Yeah, but then again I did use Croft gear in most cases during the development ;).

[Covenant]

Yeah, but then again I did use Croft gear in most cases during the development ;).

Well that explains things!:)

[walpurgis]

Pre-amplifiers should be regarded as a necessary evil.

You need one, even if its just the pre-amp stage in your integrated amp, as you have to select inputs and control levels, but its still another link in the chain.

The best sounding pre-amp of course, is the one with the least impact on the signal passing through it.

Currently TVC stages are finding favour and I've just ordered one to see what the fuss is about.

I have four very good pre-amps but they each sound different and which power amplification I feel happy using with them is different in each case.

I have made several passive pre's as well and they also have their place, although as somebody pointed out they can sound lacking in body, but that depends more on what power amp you match them with.

[Covenant]

I am thinking about trying the Lighter Note preamp. I have read reports that it is superior to TVC's.

[Puffin]

Jerry, ....on a Lighter Note....:) you already have one. The LN is an LDR pre as is the Lightspeed.

[Covenant]

This is from another AOS thread Rob (but feel free to tell me if I am wasting my money!)

In theory the Lighter Note is the ultimate passive attenuator as it only has a single component in the signal patch (one LDR per channel, it has adjustable impedance, adjustable volume range, adjustable channel balance, and a low noise power supply that incorporates a current source for the LDR's. It also incorporates a novel solution for preventing high frequency roll-off caused by the capacitance of input signal cables. All of this should mean that the Lighter Note has the minimum possible negative effect on the audio signal while allowing a great deal of flexibility in the way the circuit can be tuned to allow it to be used with a much wider range of sources and amplifiers than the standard Lightspeed Attenuator.

[synsei]

I've owned two pre-amps in recent years, an Audiolab 8000c and the Classe DR5 mk2 I have now. I've used both to drive the Hafler with very different results. The 8000c had its good points, it sported a very fine Class A headphone amp which employed discreet components throughout and the phono stage was pretty good too, however this was marred by a veiled and grainy presentation from the pre-amp circuits. Facilities and build quality were excellent. It was only when, out of curiosity, I switched to using my Caiman as a pre-amp that I discovered just how much the 8000c was hobbling my system.

Compared to the 8000c and other pre-amps I've heard the Classe is in a league of its own. Designed by Classe Audio founder Dave Reich, it lets the music breath without imparting any character of its own, which is the sign of a good pre so I am told. Since acquiring an Amptastic Mini-T the whole system has really come to life. I could wax lyrical about the DR5 for a very long time but I won't, I'm too busy enjoying the music. If you ever find yourself in north Northamptonshire why not pop in for a listen, you won't be dissapointed? ;)

[julesd68]

+1. Virtually all passive preamps I've heard make for a soft sound, lacking in drive and dynamics, compared with the best active designs. However, it can be different when a passive preamp and power amp have been designed to work together by the same manufacturer.


Indeed - the Icon Audio passive pre I tried was as flat as a pancake and this well and truly put me off trying any more ... :(

Saying that, the one passive pre I would like to listen to is the Music First which whilst fairly expensive has a small army of admirers and looks beautifully constructed ...

http://www.mfaudio.co.uk/classic.htm

Then of course there are the NVA passive pre's which by all accounts work very well with NVA power amps.

[Covenant]

I've owned two pre-amps in recent years, an Audiolab 8000c and the Classe DR5 mk2 I have now. I've used both to drive the Hafler with very different results. The 8000c had its good points, it sported a very fine Class A headphone amp which employed discreet components throughout and the phono stage was pretty good too, however this was marred by a veiled and grainy presentation from the pre-amp circuits. Facilities and build quality were excellent. It was only when, out of curiosity, I switched to using my Caiman as a pre-amp that I discovered just how much the 8000c was hobbling my system.

Compared to the 8000c and other pre-amps I've heard the Classe is in a league of its own. Designed by Classe Audio founder Dave Reich, it lets the music breath without imparting any character of its own, which is the sign of a good pre so I am told. Since acquiring an Amptastic Mini-T the whole system has really come to life. I could wax lyrical about the DR5 for a very long time but I won't, I'm too busy enjoying the music. If you ever find yourself in north Northamptonshire why not pop in for a listen, you won't be dissapointed? ;)

Thanks Dave,
Your comments on the Audiolab indicate that the preamp in the Caiman is more than passable, which confirms what I thought. Stan deserves more credit than he gives himself! So it looks like I will have to follow Marco's suggestion to better it. Either spend £1K+ or buy a Croft.

[synsei]

Thanks Dave,
Your comments on the Audiolab indicate that the preamp in the Caiman is more than passable, which confirms what I thought. Stan deserves more credit than he gives himself! So it looks like I will have to follow Marco's suggestion to better it. Either spend £1K+ or buy a Croft.

Indeed Jerry, Stan has designed an excellent pre circuit for the Caiman. It too is very transparent however within my system it just lacks a little weightiness to the bass, and of course it has no input to hang a phonostage on, which is how I ended up with the DR5 ;)

[MartinT]

At least it doesn't cause the Croft fuse to blow which is what seems to happen with most preamps I have tried. :(

That confirms that the preamps are putting more drive into your Croft and you are simply demanding too much of it. You need a more powerful amp.

[Covenant]

That confirms that the preamps are putting more drive into your Croft and you are simply demanding too much of it. You need a more powerful amp.

I am confused by this. My system is in a small room, I dont play music very loud and the speakers are efficient. The fuse blows when the amp is switched on but doesn't if the power amp is powered up last of all. :mental:

[MartinT]

Oh - new information. You didn't say that! So really what is happening is the switch-on thump from the preamp is blowing the power amp's fuse? That's quite common, which is why you always turn a power amp on last of all, and off first.

EDIT: I even have my Power Plant programmed to switch my Chord on after a 3s delay, and off first.

[synsei]

I had the same problem with the Hafler Jerry which is why I use the procedure described above by Martin. The Mini-T seems to be immune to it (discovered this during a short power outage) although I don't take any chances...

[Covenant]

Sorry, I should have explained better. Luckily you don't have to open the case to replace a fuse in the Croft.

[louie3]

I have a TVC (Stereo Knight), an Audio Research LS 7, and an Audible Illusions 2D.

The TVC has only one input, so I built an input selector box I connect to the TVC with a very short interconnect.

If I get bored for a change, I put one of the active preamps into the system, but it never seems to last long.

After listening to the TVC, either active preamp seems to add a slight layer of noise or grit to the signal, and, despite what I would have thought, the TVC seems to have deeper, better defined bass.

I am phono only (with two tuners)....but....my tube amps require less than .5 volts to full chat, and the Classe' DR8s I use now and then require less than .8 volts. So there is a direct relationship to the input sensitivity of the amps and the suitability of any kind of preamp that does not add gain.

In my experience, a TVC, even a relatively inexpensive one, sounds better than either of the active preamps I have...maybe a newer active would be better than the TVC, but I doubt I will know.

[Puffin]

This is from another AOS thread Rob (but feel free to tell me if I am wasting my money!)

In theory the Lighter Note is the ultimate passive attenuator as it only has a single component in the signal patch (one LDR per channel, it has adjustable impedance, adjustable volume range, adjustable channel balance, and a low noise power supply that incorporates a current source for the LDR's. It also incorporates a novel solution for preventing high frequency roll-off caused by the capacitance of input signal cables. All of this should mean that the Lighter Note has the minimum possible negative effect on the audio signal while allowing a great deal of flexibility in the way the circuit can be tuned to allow it to be used with a much wider range of sources and amplifiers than the standard Lightspeed Attenuator.

OK, the LN has some bells and whistles that your LS doesn't have. But the principle is the same, no moving parts in the signal path, only Light Dependant Resistors.

[wee tee cee]

Jerry,
I found an active pre made a sizeable improvement on my set up.It brought everything alive and opened up the sound giving it texture and granular quality to voices.I had a caiman in situ for a short while and felt it quelled dynamics quite noticeably.my tuppence worth.....

[Covenant]

Jerry,
I found an active pre made a sizeable improvement on my set up.It brought everything alive and opened up the sound giving it texture and granular quality to voices.I had a caiman in situ for a short while and felt it quelled dynamics quite noticeably.my tuppence worth.....

Which one do you use Tony? The more ideas the merrier!

[sq225917]

In the past three years I've variously owned and used.

Naim Nac 72
Naim Na 72 with NJ boards and local regs
NA NJ mini motherboard with quad rail for the NJ boards
A very high spec Pass B1
XTC Pre-1 (modded)
A krell KSP-7b
Shalco based stepped attenuator unit.

and I also had a load of a Puresound L10 from Guy.

They all sounded different, the stepped-pot and B1 being the clearest sounding, but the others having more bite and drive.

[jaym481]

I am phono only (with two tuners)....but....my tube amps require less than .5 volts to full chat, and the Classe' DR8s I use now and then require less than .8 volts. So there is a direct relationship to the input sensitivity of the amps and the suitability of any kind of preamp that does not add gain.

In my experience, a TVC, even a relatively inexpensive one, sounds better than either of the active preamps I have...maybe a newer active would be better than the TVC, but I doubt I will know.

I`m with you here. My 300B SET is .8V and my Leak is .125. On either the majority of active preamps I`ve tried (SS and valve) have been unsatisfactory. I`ve used a Rothwell passive and now a McCormack, which has a built in buffer (though I haven`t tried it), so it can drive long cable runs.

A well designed passive can be a real eye opener, but it needs to be paired with the right amp, and cabling is more important than other applications.

[Bluedroog]

Adding a Croft 25 was a significant upgrade in the context of my system. Previously I had tried a Caiman and AVR in direct mode as make-shift pre stages, both sounded flat, lifeless and just lacked sparkle. Introducing the Croft gave the sound much more punch and excitement, it improved in every audible area. Bass particularly gained a lot more authority.

[Covenant]

Adding a Croft 25 was a significant upgrade in the context of my system. Previously I had tried a Caiman and AVR in direct mode as make-shift pre stages, both sounded flat, lifeless and just lacked sparkle. Introducing the Croft gave the sound much more punch and excitement, it improved in every audible area. Bass particularly gained a lot more authority.

Thanks Christian,
Was your Caiman upgraded? Gator, Silmic 2's, linear power supply etc? Just wondering if the improvements make the benefit of the 25 less significant.

[wee tee cee]

Which one do you use Tony? The more ideas the merrier!I use a musical fidelity m1 hpa.It is a head amp but can be used as a single input pre. has a wee dac built in as well.

[kininigin]

I'll echo what most have said here,that a dedicated active pre can make a world of difference in improving your system.

I used to run a Beresford TC 7520 direct into some active monitors and it sounded great.When i put a micro basic inbetween there was a big step up in all areas,this was follwed by the micro 25 which again was a big step up.

The croft is so central to how my system works,that i wouldn't dream of going back.You have the power amp,would make sense to go with a croft,whether it be a basic or otherwise,you will not be dissapointed if you went this route,or with any well made pre,i would imagine.

[Bluedroog]

Thanks Christian,
Was your Caiman upgraded? Gator, Silmic 2's, linear power supply etc? Just wondering if the improvements make the benefit of the 25 less significant.

Standard Caiman, no mods or fancy power supplies.

To be honest the pre took things to another level all together, the kind when the Mrs walks in and says 'I can actually hear a difference this time'. As apposed to 'as long as it makes you happy...'

[StanleyB]

If you are using the TC-7520 or Caiman with a power amp you can plug the fixed output of the DAC into a preamp. If you are using an integrated amp you can plug the fixed output from the DAC into the AUX or CD input at the back of the integrated amp.
You don't need a preamp between the TC-7520 and Caiman if you are using an integrated amp.

The above is to clarify the situation for a few people who emailed me to ask for suggestions on suitable preamps for connection between the DAC and their integrated amp.

[Nevalti]

Surely ( if you start with 'surely' it must mean you don't know what you are talking about :wheniwasaboy:), surely, if you have chosen the right DAC and you have chosen the right power amp, you get the 'right' sound.

Having chosen those components and ended up dissatisfied, you need to modify it somehow. A pre-amp will obviously change the sound, as will cables and interconnects - but why do you want to change the sound?

Surely (there's that word again) if you need a pre-amp to get the sound you want, you haven't chosen the 'right' components in the first place. If 'simpler is better', and it usually is, why not choose your main components to avoid needing a pre-amp? I am of course assuming that you do not need multiple inputs - except maybe multiple digital inputs to the DAC.

The only analogue component I use now is an FM tuner but I get around that problem by feeding the analogue FM line into the back of my Sonos and then onto the Benchmark DAC 1. It MAY not sound quite as good but it is far better than the vast majority of internet radio and vastly better than DAB:spew:

[Covenant]

I am pleased with the SQ I get from my DAC and power amp Martin but I wouldn't be on this forum if I didn't believe there was something better. Achieving that may not be easy or cheap but that's half the fun I think.
With all the upgrading that's been done to my Beresford Caiman I am of the opinion that it will give many mid priced preamps a run for their money. No doubt I shall try a few before Stan launches his Bushmaster Plus on the unsuspecting public!

[Reid Malenfant]

A pre amp provides, or should, the impedance matching between the front end component & the power amplifier.

This isn't easy to achieve if you happen to be using some kind of DAC with a variable output, simply because the output impedance of the DAC is likely to be quite high as the volume control tends to be at the output of the DAC.

A good pre amp will not load the front end component unduly, letting it perform as it was designed to. It should also have a low output impedance, capable of driving a much lower impedance than a front end component would ever face.

So, if you like they provide impedance matching as well as a volume control, nearly forgot the switching :)

A good pre amp is invaluable imho.

[realysm42]

What's impedance matching?

[DSJR]

Wot Mark said!!!!!!!!!

Five pages? Just read the above post and take it in :respect:


As I understand it, the source device should ideally have around one hundredth the output impedance of the input device, although I believe you can just about get away with a tenth i.e output imp. of 1K on the source to 10K on the amp. If the ratio is taken to low, the frequency response suffers and I believe the sources ability to drive longer cables is compromised. This and absolute phase together can account for many "differences" we hear. I can "hear" a difference between my DCD1520 CD player analogue outputs compared to the ton-up twin supplied QED Digit DAC despite both units having 5532 op-amp outputs. This "difference" was actually more in the fact that one unit was anti-absolute phase to the other and correcting this crudely at the speaker connections to favour the other source reversed the "differences" I thought i heard - if that makes any sense to you chaps......

[Reid Malenfant]

What's impedance matching?
Ah... Good question :eyebrows:

By the way Dave, cheers for the thumbs up!


Ok, your typical bit of front end kit isn't engineered to drive a low impedance without some kind of frequency rolloff at the extremes. They'll happily drive a standard 47K Ohm load, but power amps are very rarely such a benign load.

You see all manufacturers of power amps tend to match their pre & power amps, but if you are going to mix & match different manufactured stuff it may not work out quite how you think ;)

An ideal pre amp would have a very high input impedance - so it doesn't load the front end component! It'll also have a very low output impedance - so it can drive any power amp!

These things aren't too hard to do, while a pre amp may need a certain amount of gain to bring low level sources up to the same level as a CD player output, the current gain needed to drive low impedance loads with a low output impedance should also be there...

Some pre amps will damn near drive speakers on there own, without a power amp as their output impedance is so low :eyebrows: They might sound like a valve amp doing it, but it's that high input & low output impedance that you need a pre amp for :cool:

[Ali Tait]

A pre amp provides, or should, the impedance matching between the front end component & the power amplifier.

This isn't easy to achieve if you happen to be using some kind of DAC with a variable output, simply because the output impedance of the DAC is likely to be quite high as the volume control tends to be at the output of the DAC.

A good pre amp will not load the front end component unduly, letting it perform as it was designed to. It should also have a low output impedance, capable of driving a much lower impedance than a front end component would ever face.

So, if you like they provide impedance matching as well as a volume control, nearly forgot the switching :)

A good pre amp is invaluable imho.

Yep, totally agree, also the reason why some don't get good results with a passive Pre, unless it has buffers on input and output.

[Ali Tait]

For instance, the WD Pre 3 I use is basically a valve amp in miniature, and provides loads of drive on it's outputs, so it'll pretty much match any source to any amp impedance wise.

[Reid Malenfant]

I should add that the low output impadance of a pre amp should drive just about any power amp, as I say, some will nearly drive speakers to a Watt or so :)

Some serious current delivery...

[Nevalti]

.....With all the upgrading that's been done to my Beresford Caiman I am of the opinion that it will give many mid priced preamps a run for their money........

That strikes me as a sensible approach (subject of course to using your ears) - avoid introducing extra components, if you can. I have little doubt that Stan is doing his best to avoid the need of a pre-amp. Stan?

On the subject of impedance matching, the answers so far are, understandably, 'short' answers and I am not criticising any of them - mainly because I have very limited electronic knowledge, but do read right to the end. It is interesting however to look at the specification of components which work well together. I intend shortly to audition a pair of Nuforce Ref 9V3s with a Nuforce DAC 9 (Using no intervening pre-amp). Every dealer I have spoken to, in the USA, Netherlands and UK assure me that this combination is truly high end without a pre-amp. Even bearing in mind that I am talking to salesmen, one would have thought that Nuforce, with currently an enviable reputation, would try to stop people using this combination and thereby spoiling their reputation IF they did not work well together. Instead of stopping people using that combination, they make it very easy. Now look at the Specs.....


Nuforce DAC 9: RCA output impedance 0.01 ohm. XLR output impedance 50 ohm.
Nuforce Ref 9 V3: Input impedance 22 K ohm.

So, if the Specs. on their web-site are right, the ratio is 22,000/0.01 = 2,200,000:1 via RCA and 22,000/50 = 440:1 via XLR. Note that neither ratio is anywhere near the 1,000:1 ratio that some advise as being ideal. For comparison, both of the high end Nuforce pre-amps (P9 & P20) have an output impedance of 100 ohm on both RCA & XLR giving a ratio of 220:1

Given my ignorance there may well be other factors involved but this very high reputation company has engineered two bits of equipment to work together at world level quality and have arranged two vastly different impedance matching ratios depending upon which connectors are used. My guess is that they do know what they are doing.

I will let you know what I think about the sound via both connectors if I end up buying this combination.:bag:

For comparison: The Musical Fidelity Primo pre-amp output impedance is quoted as 600 ohm. That is 60 million times higher than the quoted DAC 9 output impedance of 0.01 ohm! To confuse matters more, I tried to look up the output impedance of some other high end pre-amps and the figures are not even quoted - not on the web-site and not even in the manuals. How on earth do you do 'impedance matching' if the figures are not available?

PS I suspect that Nuforce have actually mis-quoted the output impedance of the DAC 9 but, whatever the figure is, it is very interesting that many manufacturers do not even quote the figure. In my ignorance, I suspect that other factors are of more relevance.

[nat8808]

0.01 to 600.00 is only 60,000 times higher..

Did you mean the output is 600 K ohm?

[Nevalti]

0.01 to 600.00 is only 60,000 times higher..

Did you mean the output is 600 K ohm?

:oops: Silly me!

MF quote the output impedance as 600 ohm so it is 'only' 60,000 times higher than the quoted Nuforce DAC 9 output impedance. Even at a 'paltry' 60,000 times higher, my observation remains the same. I am tempted to ask a similar question - what on earth is the importance of impedance matching? :scratch:

[Reid Malenfant]

It's not actually about getting the output impedance of one device to equal the input of the other, quite the opposite in fact :eyebrows:

What you need to make sure of is that the output impedance of your front end kit is low enough so that the input impedance of the pre amp will in no way load it too much & affect the sound.

Now assuming you have a device with an output impedance of say 100 ohms, & that's driving a pre amp with an input impedance of say 47K ohm or 47,000 ohms... There is no way on this earth that the pre amps input impedance is going to affect the signal from the front end, it has miles too high an impedance.

On the other hand, some valve kit may well have an output impedance of over 1K ohm & this won't be very happy driving a pre amp with a low input impedance of say 10k ohm. What will happen is that the audio frequency extremes will tend to roll off somewhat, this is due to filtering that is often used to block DC & avoid extremely high frequencies that may damage an amplifier (ultrasonics).

I'd suggest that as long as you have an output impedance to input impedance of 50:1 then you'll be fine, less than 10:1 & you may notice it ;)

[MartinT]

A pre-amp will obviously change the sound

No, a good preamp can be incredibly transparent. What it will do is provide more drive, dynamics and tonal shadings than a passive setup by correctly matching the inputs with the power amp.

[synsei]

+1 :)

[Nevalti]

No, a good preamp can be incredibly transparent. What it will do is provide more drive, dynamics and tonal shadings than a passive setup by correctly matching the inputs with the power amp.

So what does 'correctly matching' mean and why do I want even more dynamics IF I have chosen well in the first place? And where does the extra tonal shading come from?

I'm not saying you are wrong. I'm just trying to understand the logic of relying on yet another component rather than getting the sound right without it.

[MartinT]

Each to their own, Martin, but it's a matter of *preserving* the signal and not throwing away parts of it. A good preamp does exactly that, by matching impedances and providing proper drive to the power amp.

Dynamics in a hi-fi system are everything. They provide the cues that make the brain think the music is real and not a reproduction. Do EVERYTHING you can to preserve dynamics, they are the life-blood of a good system.

[Nevalti]

Each to their own, Martin, but it's a matter of *preserving* the signal and not throwing away parts of it. A good preamp does exactly that, by matching impedances and providing proper drive to the power amp.

Dynamics in a hi-fi system are everything. They provide the cues that make the brain think the music is real and not a reproduction. Do EVERYTHING you can to preserve dynamics, they are the life-blood of a good system.

Please don't misunderstand, I am not saying anyone is wrong, I am simply trying to understand why adding a component is a good thing.

Maybe it is just my ignorance but I don't understand how 'dynamics and shading' can be added AND be more faithful to the original signal. IF we know with certainty that something has been lost, maybe we can use an extra component to try to recover it. IF we don't KNOW something has been lost we are just manipulating to get the sound we desire. Nothing wrong with doing that but it strikes me as less than ideal.

Obviously I am ignoring phono stages and switching. My comments apply to the use of a good DAC/pre without introducing a separate pre-amp.

[MartinT]

Maybe it is just my ignorance but I don't understand how 'dynamics and shading' can be added AND be more faithful to the original signal.

You're still getting the sense of what I'm saying wrong. A preamp loses *less* than other means, is what I'm trying to get over. So it doesn't add anything, it preserves more.

[Covenant]

Another way of looking at it is that an integrated amp will be perfectly matched impedence-wise so why bother with a separate pre amp?

[Yomanze]

Another way of looking at it is that an integrated amp will be perfectly matched impedence-wise so why bother with a separate pre amp?

Pre / power combos offer a higher ceiling of performance than integrated amps.

[synsei]

Another way of looking at it is that an integrated amp will be perfectly matched impedence-wise so why bother with a separate pre amp?

It would take a very special integrated amp indeed to persuade me to give up the DR5 and such a beast would probably be way beyond my budget anyway so I'm more than happy with my current set up ;)

[Covenant]

Pre / power combos offer a higher ceiling of performance than integrated amps.

Why? (not disagreeing-I would just like to know):)

[Ali Tait]

Separation of Pre and power signals for one.

[MartinT]

And separation of completely different power supplies.

[bobbasrah]

And separation of completely different power supplies.

Sorry, a big assumption Martin. Some are entirely separate.;)

[MartinT]

Sorry, a big assumption Martin. Some are entirely separate.;)

Agreed, Bob, but they are in the minority. Most integrated amp power supplies share at least the transformer, if not the primary rectification and regulation.

[Reid Malenfant]

Agreed, Bob, but they are in the minority. Most integrated amp power supplies share at least the transformer, if not the primary rectification and regulation.
& I'm 100% damn sure that they share the same power lead :eyebrows:

Not a good thing imo...

[Nevalti]

You're still getting the sense of what I'm saying wrong. A preamp loses *less* than other means, is what I'm trying to get over. So it doesn't add anything, it preserves more.

That is in a sense very close to the old adage that 'an ideal amplifier is a straight wire with gain'. In the case of a pre-amp used with line level inputs, it should of course be changed to 'a straight wire with attenuation'. In which case, I guess you are saying that a good pre-amp preserves the signal accurately by attenuating it appropriately rather than just putting a simple resistor (variable or otherwise) in line?

I have no idea of the full effects of putting a simple resistor in line - does anyone here know the theory? I always imagined that it would have no effect on the 'tonal shading' or dynamics. There are numerous resistors in amplifiers, are we to assume that they all degrade the signal and that a pre-amp is there to recover what will be lost by the power-amp? Hardly likely as power amps differ dramatically in their dynamics.

IF then, ignoring switching, the purpose of a pre-amp is to provide attenuation, is it really necessary to spend thousands on one? Isn't it rather like spending thousands on interconnects etc to change the sound? The ideal wire adds nothing and loses nothing, surely a pre-amp should do the same; unless of course you actually want it to change the sound.

Manufacturers of some line level source components claim to tailor the signal so that an expensive pre-amp is unnecessary. They may or may not suceed very well but using an expensive pre-amp with such equipment should make the sound 'wrong' but maybe it is still more to some people's liking - and there is nothing wrong with that. Some of us prefer to sit in row 'M' and some of us prefer to sit right at the front.

[StanleyB]

I have no idea of the full effects of putting a simple resistor in line - does anyone here know the theory? I always imagined that it would have no effect on the 'tonal shading' or dynamics.
A simple example and common situation where a resistor is used in line to alter the dynamics of a circuit is in power supplies. The resistor can dramatically cut down the dB level of noise peaks. Unfortunately it also causes a voltage drop. So more advanced circuits might use an inductor instead since a the inductor is only supposed to work on the AC part of the signal if it is a DC power supply or specific parts of the AC frequency range if it is an AC power supply.

Since audio frequency is also AC, the above condition are also valid. Some headphones rely on an in-line resistor to reduce the dynamics for whatever reason. This in itself has generated various modification topics on forums on how to remove or bypass the resistor in order to improve the dynamics of the headphone. The MDR-F1 that I own is a typical example of where an in-line resistor has been used to alter the dynamics.

Obviously, if you alter the dynamics you also alter the tonal shading. The signal before and after the resistor will look different on a scope.

A passive preamp, which relies on a variable resistor, is another case in point. The sound before and after the preamp sounds different, primarily softer. No doubt this is as a result of a reduction in dynamics brought about by the resistive path introduced.

[Nevalti]

.......... Obviously, if you alter the dynamics you also alter the tonal shading. The signal before and after the resistor will look different on a scope.

A passive preamp, which relies on a variable resistor, is another case in point. The sound before and after the preamp sounds different, primarily softer. No doubt this is as a result of a reduction in dynamics brought about by the resistive path introduced.

Thanks Stanley, that is very useful.

So, for digital only listening, the question seems to be: Which combined DAC/pre-amps will spoil the sound in this way and which will perform well without a separate pre-amp? AND if the DAC/pre does not have a specific pre-amp by-pass, will it spoil the sound, when used with a separate pre-amp, even if the 'volume control' is set to maximum?

I have long assumed that a well designed combined DAC/pre-amp would not 'benefit' from a separate pre-amp although it will probably sound different if you use one. In the case of my Bryston, the pre-amp adds warmth and spoils imaging compared with using my Benchmark DAC1 and by-passing the pre-amp.

[falcoron]

As I have a Croft power amp the Micro is the obvious choice. However it's nice to try a few alternatives before settling with one of Glenn's offerings!

Jerry, you will go round and round the pre amp mulberry bush mate, save yourself the hassle and get the croft it will match and have synergy, Croft stuff is superb but fussy with others. My pre amp journey although short was WAD but that was emmm well forgetable! Glass house TVC which was brill and i was happy until i tried active, the whole thing just lifts and give a bigger better sound all round, then i bought an XTC pre 1 which is a great pre amp for the money, gotten the bug now and have just bought an AN M2 Special edition and it is gob smackingly good so much so im now saving for an M3 and i wont stop til i get a 5. Pre amps are they worth it difficult to say as they range from Feck all to 100's of 1000's, But in my opinion they are VITAL! if you want to get the best from your system do a bit of research get one that matches and you WILL get the best from your system.
Hope that helps
Ron

[Covenant]

I have long assumed that a well designed combined DAC/pre-amp would not 'benefit' from a separate pre-amp although it will probably sound different if you use one. In the case of my Bryston, the pre-amp adds warmth and spoils imaging compared with using my Benchmark DAC1 and by-passing the pre-amp.[/QUOTE]

In my case I find that a separate pre-amp widens the soundstage a little but does little to alter the dynamics. The cost does not seem to be justified.

[StanleyB]

Whether a separate preamp would be beneficial is a different kettle of fish. What is beneficial is a separate preamp section in a DAC.
As it so happens, whilst I type these lines I am also busy designing a separate preamp section for my own Bushmaster DAC. I tried the passive variable output as used on the Caiman etc. but the the more musical Bushmaster is showing up the disadvantages of that approach. I also tried converting the headphone amp circuit into dual use mode. But again, the circuit layout for a headphone is of no use as a preamp.
So I am having to bite the bullet and design a proper preamp circuit just to drive the variable output, and nothing else.
Why is that, some may wonder. Well, it turns out that preamps need to have a low output impedance in order to drive difficult loads presented by some interconnects (including varying length), and to also provide a proper fixed impedance matching ratio with the poweramp, irrespective of the volume control setting on the preamp. A passive volume control doesn't do that, and a headphone amp output is geared towards loads of say between 32 Ohms to 1200 Ohms. Power amps are anywhere between 2K to 100K. So different design rules apply. Separate preamps are designed to take this into account. Built in preamps in DACs do not as far as I can see from looking at circuit diagrams or layouts of commercially available DACs out there. Maybe there are a few, but I know of none. Which explains why so many people seem to benefit from a separate preamp with its low output impedance, and why I am trying to come up with an alternative solution after having tried the various design combinations possible.

[Covenant]

As it so happens, whilst I type these lines I am also busy designing a separate preamp section for my own Bushmaster DAC


Looking forward to this..........

[Nevalti]

............ I am also busy designing a separate preamp section for my own Bushmaster DAC. ................. Built in preamps in DACs do not as far as I can see from looking at circuit diagrams or layouts of commercially available DACs out there. Maybe there are a few, but I know of none. Which explains why so many people seem to benefit from a separate preamp with its low output impedance, and why I am trying to come up with an alternative solution after having tried the various design combinations possible.

That sounds exactly what I need! Thanks for the clarification Stanley.

I wonder if I can wait patiently enough or will I succumb to the Nuforce DAC9 that I intend to audition soon with the Nuforce Ref 9 amps:hmm:

[walpurgis]

Here's my current solution to the pre-amplifier question.

http://i49.tinypic.com/op1l00.jpg

http://i49.tinypic.com/2emcyl0.jpg

My recently aquired Mei Xing TVC passive pre-amp. It sounds very good, as transparent as my Class A Forte Model 2, which up to now was without doubt the most open sounding pre I'd used. It doesn't seem short on the bottom end as do many potentiometer based passives.

[MartinT]

I really dislike the term 'Passive Preamp'. They are nothing of the sort as they contain no active components. 'Volume Control' or 'Attenuator' are more appropriate phrases.

[Stratmangler]

I really dislike the term 'Passive Preamp'. They are nothing of the sort as they contain no active components. 'Volume Control' or 'Attenuator' are more appropriate phrases.

I quite agree with you.
I also get slightly niggled when I hear the term "vinyl rip", as there's no such thing.
Needledrop I'm fine with, but rip - no f**king way ;)

[walpurgis]

I do apologise Martin, consider me chastised. 'Passive pre-amp' seems to be a generic term these days for what you properly describe as a "volume control".

[MartinT]

I wasn't getting at you, Geoff. As you say, many people use the misnomer.

[Reid Malenfant]

Certain passive pre amps can sound rather good indeed :) The thing is though, they need to have a constant impedance & they need to be tailored to the impedance of the load that they'll be driving.

As long as these are met then it won't matter a fig what volume setting you are at, as the source will see a constant impedance over the whole volume range & will perform the same at any volume.

It'll still need to have a much lower output impedance than the volume control is designed for though. Assuming you are driving a 22K to 47K ohm load then an output impedance of less than 500 ohms should be ok.


You need to realise though that whatever is driving the power amp needs to be able to take it to full volume & some. While a CD output (2V) could do this with most power amplifiers, some kind of active gain would still be needed with just about any other front end kit like cassette decks or tuners etc, as these tend to output only 200mV :rolleyes:

So pre amps of the active variety still & always will have their place :)

[walpurgis]

I've got a rather nicely made 50k log, stepped, resistor dual attenuator which I keep meaning to try. Must get around to it.