Anyone interested in a DIY valve line stage?

[Arkless Electronics]

I have a design for a valve line stage, with gain, which I designed many years ago and which I'm willing to put into the public domain for AOS DIYers... if there is enough interest.

As some will be aware I don't personally use line stages and prefer a passive but there are many out there who swear by active line stages and so this is for them;)

I designed it as a project to get a close friend into a bit of audio diying and hence it is very simple.

[Arkless Electronics]

Ok no interest so forget it....

[Puffin]

Whoa Jez, don't be so hasty. I have just got back from holiday. I would be interested.

[Arkless Electronics]

Whoa Jez, don't be so hasty. I have just got back from holiday. I would be interested.

If it gets up to a dozen or so interested then I'll take it further;)

[Marco]

Quite frankly, I think you've giving folks WAY too much time to see the ad and make up their minds! :D :doh:

Posted yesterday at 18.24, withdrawn today at 19.23...

Marco.

[Arkless Electronics]

Quite frankly, I think you've giving folks way too much time to see the ad and make up their minds! :D :doh:

Marco.

Ha ha:D... and it's not an ad cos it's a freebie:) To be honest I just can't be arsed with the work I'll have to put into presenting it and giving build advice etc if only a few people are interested anyway...

[Marco]

Lol - you are a daftee.... Just a wee suggestion, you might've got more interest if you'd made the proposal in the DIY section ;)

You're not 'wedded' to your trade room, you know! :eyebrows:

Marco.

[Puffin]

If it gets up to a dozen or so interested then I'll take it further;)

Nice one.

[Arkless Electronics]

Lol - you are a daftee.... Just a wee suggestion, you might've got more interest if you'd made the proposal in the DIY section ;)

You're not 'wedded' to your trade room, you know! :eyebrows:

Marco.

AFAIK it is in the DIY section! Is this not what "The Drawing Board" area is?

[Barry]

I would be interested. :)

[smangus]

If it's completely numpty proof I'd give it a shot :eek:

Never tried anything electrical beyond fitting a light bulb (this would please the missus!)

[Sovereign]

I would also be interested.

[tubehunter]

..

[paulf-2007]

When you've retrieved your teddy from the corner maybe you could give us some info :)

[Arkless Electronics]

When you've retrieved your teddy from the corner maybe you could give us some info :)

:upyours:

[Greg2010]

One more to the list

[Arkless Electronics]

I'll post a brief circuit diagram for perusal shortly :)

[User211]

Did you ever make it?

[Arkless Electronics]

Did you ever make it?

I guided my pal through building one yes and made measurements on this example. It was at least 20 years ago.... Tempus fuckit etc...
It sounded good and AFAIK is probably still in use!
I made detailed notes at the time;) With hindsight and the passage of 20+ years + the fact that this is intended as a really simple project, I have made some amendments and simplifications intended to both improve performance further and ease construction. These changes have not been tried in practise but will work just fine. My CAD model for the ECC88 valve used is pretty accurate and so the computer simulation can be trusted to be very close to real life in this case.

I guess I'll knock up a working sample to have a listen to and double check the measured results etc. It will make things easier in helping others to make one... What have I gotten myself into:doh::)

[Puffin]

What have I gotten myself into:doh::)

Get away......you're lovin' all the attention :D

[Arkless Electronics]

Here it is:)

http://i1303.photobucket.com/albums/ag156/Jez1235/DIY%20pre%20for%20AOS%203-9-16_001_zpsebey8s6u.jpg (http://s1303.photobucket.com/user/Jez1235/media/DIY%20pre%20for%20AOS%203-9-16_001_zpsebey8s6u.jpg.html)

Obviously this shows just the meat of the thing and does not show the power supply detail or selector switch, phono sockets etc but it shows how nice and simple it is... but elegantly I think;) Now't new or "no one's done this before", just, I hope, sound engineering of the K.I.S.S type.

The valve is a dual triode so there is just the one valve.

[Arkless Electronics]

Get away......you're lovin' all the attention :D

:D Oh luvvies, dahlings:lol:

[Arkless Electronics]

Specifications:

Gain 10dB (x3)
Output Impedance 520R
THD <0.01% @ 2V RMS out into typical 47K load. <0.1% into 10K load
Frequency response <-1dB 5Hz-100KHz into 47K

Not half bad for a super simple one triode per channel pre amp I think you will agree:)

I should point out that this is not intended to be "ooh listen to that euphony and warm roses in me contact lenses valveyness" ;) More "straight wire with gain but with a hint of valve, sounds more like SS but without any SS grain/grit/greyness". If folks want more of the former I will show a few things to drag the poor thing more in that direction later:)

[tubehunter]

..

[Arkless Electronics]

Plenty of feedback

not much drive

how about a cathode follower




and a constant current

eg:
http://i514.photobucket.com/albums/t350/halx00/croft%20pre/IMG_6058_zps3chdeust.jpg (http://s514.photobucket.com/user/halx00/media/croft%20pre/IMG_6058_zps3chdeust.jpg.html)

Yours has roughly the same feedback, no constant current source, an input impedance of only 10K and actually has far less drive potential in practice than my suggestion;) It would work well though yes but I've no reason to believe it would be any better than my simpler offering and suspect that in practice it would be slightly less good.

1/ The main principle here is K.I.S.S. Yours is twice as complicated for a start and needs 2 valves.
2/ I'm doing this on some sort of strange whim which I haven't really analysed myself :doh:.. maybe to put something back for the site in appreciation of Marco's assistance in erm certain things:) It is NOT intended to be a "lets all uber analyse the circuitry and then suggest our own alternatives and design a horse by committee that turns out more of a camel that's no longer suitable for the DIY beginner"

3/ As someone who does this for a living I'm not going to design something unique, a new topology, patentable and then put it in the public domain! It is good sound non ground breaking engineering and several high end amps have used a similar topology in the past:)

[Arkless Electronics]

Here it is with power supply and both channels.

http://i1303.photobucket.com/albums/ag156/Jez1235/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_2_zpshtyzqgsc.jpg (http://s1303.photobucket.com/user/Jez1235/media/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_2_zpshtyzqgsc.jpg.html)


Nice and simple;) May be subject detail changes... but that's about it. Note that there is only one physical valve as it is a dual triode. U1 and U2 are actually left and right halves of the same valve. Same with vol control R6 and R12 if a dual gang control is used. They can of course be separate left and right vol controls or even a switched attenuator for even better results.

[Firebottle]

That's about as good as it is going to get for a KISS design line stage :thumbsup:

You could omit C1 and C3 if you are paranoid about having electrolytics in circuit, and expect a nads less gain.

Good one Jez :)

[Arkless Electronics]

That's about as good as it is going to get for a KISS design line stage :thumbsup:

You could omit C1 and C3 if you are paranoid about having electrolytics in circuit, and expect a nads less gain.

Good one Jez :)

Thanks Alan:) I think it will sound really nice too. The original did and this has a few detail improvements.

I spent a bit of thought on exactly that re the cathode caps but decided to keep the output impedance low and drive as good as possible. Yes it would work fine and is an option though.
A valve diode in line from the output from the SS rectifier would obviate the need for the two Zener diodes... a valve rectifier instead of the SS would do this just as well also. Both add to cost and complexity though...

[Arkless Electronics]

Oh and it's ideal for those wishing to experiment with "boutique" components as so few are needed! Seven per channel are all that's "in the signal path"...

[Arkless Electronics]

Some feedback from all the people who said "I'm interested " would be useful around this point in order to get to grips with how people would want a practical implementation to be, what help is needed to "make it so" and any other questions people have really:)

[Puffin]

Jez, I have built tons of SS stuff point to point and would propose to build this on perfboard. I have only built one valve based headphone amp and that was on a PCB. I follow all of your schematic apart from the power supply. The heater supply is 6.3v, but the supply to the rest of the circuit is not marked with voltages. Are all the resistors 1/4 Watt or should they be higher.

[Arkless Electronics]

Jez, I have built tons of SS stuff point to point and would propose to build this on perfboard. I have only built one valve based headphone amp and that was on a PCB. I follow all of your schematic apart from the power supply. The heater supply is 6.3v, but the supply to the rest of the circuit is not marked with voltages. Are all the resistors 1/4 Watt or should they be higher.

This is the kind of stuff I need to know from potential constructors:)

First of all I don't intend to do a PCB for it but others are welcome to design one if they want to do it that way. It will need to be two separate PCBs ideally, one for the PSU section and one for the main circuitry for mains hum etc reasons.
I guess it would make it easier for total novices if there was a PCB with all the socketry on it etc but I'm afraid I can't be arsed with such a long procedure for something that A/ I'm giving away free and B/ I have no need for a PCB myself... I welcome others contribution on these lines though. Please do let me approve any PCB design for correct layout from an electrical POV;)

Perfboard will do fine as will tag strip. I'll do one on tag strip as I have a suitable chassis with everything on it already which will make it dead easy for me to knock up a working sample.
I will add voltages as it will help in fault finding. The resistors are not all 1/4W and I will also add that info. Sorry for the misaligned script but the conversion process to PDF and then JPEG seems to knock some writing off grid!

Here's a nice transformer for it: http://www.ampmaker.com/store/240V-6.3V-toroid-power-transformer.html

[Arkless Electronics]

Here's the requested Voltages etc. Other channel identical.

http://i1303.photobucket.com/albums/ag156/Jez1235/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_001_zps8sehkbcc.jpg (http://s1303.photobucket.com/user/Jez1235/media/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_001_zps8sehkbcc.jpg.html)

Voltages in red, the other Voltages are of course the ratings of the capacitors. WW is wirewound. The anode resistors can be a variety of things "to taste" as long as capable of handling 2W. The other WW types are not in signal path. All other resistors are 1/4W

[Arkless Electronics]

Having checked the datasheet for the ECC88 it seems it's rated up to 550V cold so we can lose the Zener diodes:) here's the amended diagram.

http://i1303.photobucket.com/albums/ag156/Jez1235/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_001_zpsxoodajhb.jpg (http://s1303.photobucket.com/user/Jez1235/media/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_001_zpsxoodajhb.jpg.html)

I'd only put them in as safety precaution but as it's safe to get rid that is a good thing!

[Arkless Electronics]

Nearly finished building the prototype :eyebrows: hopefully up and running before the end of the night..

[topoxforddoc]

OK, Jez, many thanks for this. As a DIY noob, is this something manageable for a complete novice (although I can wield as ordering iron)? Is this a single input unit?

Cheers

Charlie

[struth]

easy enough to add more Charlie:)

[Arkless Electronics]

OK, Jez, many thanks for this. As a DIY noob, is this something manageable for a complete novice (although I can wield as ordering iron)? Is this a single input unit?

Cheers

Charlie

It's as simple as it gets for an active pre amp and is fairly unfussy about construction techniques so I guess it's suitable for a noob yes. My dread is if people need help down to the "take a length of red wire and cut to 3" long, bare 1/4" of each end..." type noob help:eek: But I'm sure we'll muddle through... I could need some help from others on explaining things for the noob as I've been doing this kind of thing for decades and it's like making a cup of tea to me... which probably makes me not the best teacher:rolleyes:

It's as many inputs as you like! I just haven't shown the selector switch and phono sockets as they are kind of "taken as read".... well.. to me.. see above...

[topoxforddoc]

It's as simple as it gets for an active pre amp and is fairly unfussy about construction techniques so I guess it's suitable for a noob yes. My dread is if people need help down to the "take a length of red wire and cut to 3" long, bare 1/4" of each end..." type noob help:eek: But I'm sure we'll muddle through... I could need some help from others on explaining things for the noob as I've been doing this kind of thing for decades and it's like making a cup of tea to me... which probably makes me not the best teacher:rolleyes:

It's as many inputs as you like! I just haven't shown the selector switch and phono sockets as they are kind of "taken as read".... well.. to me.. see above...


Thank for the rapid reply. Realistically what would you project the build/component cost to be approx (excl valves, which can vary enormously), assuming some decent, but not OTT components? It would be fun to have a go with something not too expensive.

Cheers

Charlie

[Arkless Electronics]

Jobs a gud 'n ;) Worked first time with all voltages within a couple of % of simulation results... Neighbour is in so can't audition it till tomorrow.

[Arkless Electronics]

Thank for the rapid reply. Realistically what would you project the build/component cost to be approx (excl valves, which can vary enormously), assuming some decent, but not OTT components? It would be fun to have a go with something not too expensive.

Cheers

Charlie

About £200. Its very much a "how long is a piece of string?" sort of thing... It could be done for less than that but a nice looking case is always the expensive bit.... Phono sockets vary from 40P to tens of pounds each... cheapo vol pot? A quid. Replace it with a switched attenuator and it's over a £100 for just that...
Resistors? 1p each for 1/4W or £12 each if bulk foil type etc etc
There is only one valve. An improved version could be made with two valves using one per channel with both halves of each valve in parallel to give twice the current drive and half the output impedance. Just need the extra valve and socket and one more resistor plus changing the value of a few resistors... Would it sound better? No idea unless I try it;)

[Arkless Electronics]

Points arising.... record out and tape monitor can be easily added as can "listen and record", it's all just switches.. Like many pres and integrateds it would be unbuffered tape out and so for ultimate sound quality it would be best not to have tape recorder or ADC connected unless you need to use them.. This applies to probably over half the amps in existence but... they don't tell you that! A switch can of course be added to switch the record out sockets on or off;) I stress again that most amps have this issue anyway....

I may put the Zeners back yet as it limits the max voltage the output capacitors have to see and therefore allows lower voltage rated caps to be used at much lower price and physical size... I'll have to see if their presence is audible due to modulation of junction capacitance.

Switch on thump could be an issue but I'm hoping I can keep it low enough without having to add a muting relay. You wouldn't want to make the mistake of switching on the power amp first though! If this aspect MUST be foolproof though it will mean the added complexity of the mute relay and associated electronics...

Mains hum. For simplicity I've used AC powered heaters on this and I'm hoping it will manage a silent background... if not I'll have to arrange DC heater supply which isn't much more effort but I'm trying to keep it as simple as possible. If the mute relay turns out to be really necessary then this will come with it as I'll have to arrange a DC supply from the heater voltage for the relay anyway...

All just thinking aloud about which areas may need extra attention..

In spite of its simplicity there is no reason this should not be the equal of active pres in the £1K+ region.. The specs are exemplary and there is the very minimum in the signal path. The proof of the pudding is in the listening of course and that will have to wait till tomorrow:)

Oh another thought is that if you already have a scrap amp/donor unit it could already have the requisite sockets, selector switch, vol control in/on it and so save loads of work and cut construction cost to maybe £70;)

[paulf-2007]

Jobs a gud 'n ;) Worked first time with all voltages within a couple of % of simulation results... Neighbour is in so can't audition it till tomorrow.
Send the neighbour home, after all they have their own home or they wouldn't be a neighbour:)

[Arkless Electronics]

The Zener idea proved good with no measurable increase in distortion for their presence :)

First impressions are it sounds fookin great!! No background noise at all even with AC heater supply. The small amount of distortion is 2nd harmonic only so thats good.

In spite of it having x3 gain the inherent 47K input impedance of the pre itself works with the 50K vol pot to give a sort of "extra log" law to the pot which means fine control of volume is actually better than my passive!

Joni Mitchell "Blue" sounding very nice indeed as I type;)

It is looking like a switch on mute relay is going to be needed unfortunately if the unit is to be used with SS power amps :(

[Barry]

Would be interested in building a version using the two halves of the E88CC in parallel for each channel, i.e. using two valves. Would that require halving of the anode and cathode resistors? Also I would prefer to use DC heaters, would a simple 6V regulator would be sufficient? I already have a circuit for the latter.

[Arkless Electronics]

Would be interested in building a version using the two halves of the E88CC in parallel for each channel, i.e. using two valves. Would that require halving of the anode and cathode resistors? Also I would prefer to use DC heaters, would a simple 6V regulator would be sufficient? I already have a circuit for the latter.

Spot on in all regards Barry.
It seems to be completely hum free even without DC heater supply but as I said above for use with SS power amps it is going to need a mute relay on the output which will need a DC supply so it looks like it will end up having DC heaters anyway.... For those certain to use it only with valve power amps the version already shown will do great and cut down on build complexity.

Well still not "run in", or "voiced" at all and haven't tried any "tube rolling" (god I hate that term!) but it is sounding very nice indeed so far...

Off out for beers with mates now :cool:

[Arkless Electronics]

Switch on delay circuitry now done. will probably post it here later. It says something as to just how simple this pre is in that the switch on delay is more complicated than the actual pre!

[Arkless Electronics]

Here's the final thing. There are a few minor changes here and there...

http://i1303.photobucket.com/albums/ag156/Jez1235/DIY%20pre%20for%20AOS%203-9-16%20with%20PS%20_001_zpsb9oiwaon.jpg (http://s1303.photobucket.com/user/Jez1235/media/DIY%20pre%20for%20AOS%203-9-16%20with%20PS%20_001_zpsb9oiwaon.jpg.html)

Bizarrely there is no suitable relay in my CAD software so the relay coil is shown as a 1mH choke and the normally closed contacts as two separate switches.

I'll leave this as job done and post no more now on construction etc until/unless anyone wants to build one and needs any assistance;)

[Arkless Electronics]

A spot of "tube rolling":)

The cast are Selectron ECC88, probably Russian or Czech, it's at least 20 years ago I bought a few of these.

Mullard ECC88

Mullard E88CC-01

The Selectron sounds good generally but I did notice a trace of "zing" to loud, high pitched female vocals.

The Mullard ECC88 completely loses this zing and seems to gain in transparency and sound staging noticeably.

On this occasion "the more expensive the better the sound" does seem to apply... The E88CC-01 has all the transparency gains and lack of "zing" of the Mullard ECC88 but seems "fuller" and to have more "oomph" (that's a technical term:eyebrows:).

Pity the cheap one didn't sound the best on this occasion....

[Radford Revival]

A neat trick in the delay circuit could be to switch the relay with a thyristor instead of a darlington pair for cleaner relay switching. Speaking from an annoying experience with a very similar circuit (actually for the exact same purpose) that switched a bit "soft" even with a darlington - whereas a thyristor would have switched on hard once pushed over its threshold. I thought of this after building the thing so it remains a darlington :rolleyes:

[Arkless Electronics]

A neat trick in the delay circuit could be to switch the relay with a thyristor instead of a darlington pair for cleaner relay switching. Speaking from an annoying experience with a very similar circuit (actually for the exact same purpose) that switched a bit "soft" even with a darlington - whereas a thyristor would have switched on hard once pushed over its threshold. I thought of this after building the thing so it remains a darlington :rolleyes:

Thanks for the suggestion Will:) I actually had considered that and dug out a packet of little T092 SCR's but found that with a "BT47" style relay it reacts well to the slowly rising voltage and switches clean enough for there to be the click one would hope for from the relay, which surprised me! The Darlington does saturate nicely BTW when the cap is fully charged. I've kept my heaters AC on mine and on the diagram and made the smoothing cap small for the delay board so it drops the relay out nice and quick when power is removed... I could probably get away with raw DC but added a bit of smoothing to keep things electrically quiet.

It's just a pity that my decision to use a non cathode follower topology, for a host of reasons, has meant having to deal with a rather large switch on thump.... we're talking 100V!:eek: And SS amps don't like that up 'em Mr Mainwaring:D

[Arkless Electronics]

Here it is in action.... breadboard chassis lash up... Yes it's supposed to look that much of a mess:D One input version to prove idea, do listening tests and perform measurements on. Freshly rolled "tubes" (valves! We're British!:D) on top...

http://i1303.photobucket.com/albums/ag156/Jez1235/2016-09-09%2017.53.01_zpsms1voynp.jpg (http://s1303.photobucket.com/user/Jez1235/media/2016-09-09%2017.53.01_zpsms1voynp.jpg.html)

Now who's going to be first to build one all nice?:eyebrows:

[Arkless Electronics]

I'm surely not the best to review my own work but I'll have a go... Warning: Jez is going to get all subjective!:D

First of all the minor changes to some values and the eventual choice in my own of a Mullard E88CC-01 have improved it considerably since my first listening. It's also had 24 hour burn in.
Well I may have to eat some of my words here as this does, in many ways, sound better than my passive! I'll start with the downside... percussive transients sound very slightly softened in comparison to the passive. Whether the passive is allowing through "edge" etc from the CD player that makes it sound harder... or the valve pre is losing something and softening it slightly I'm not sure yet!

And the upside... It sounds simply stunning overall! Images are projected in front of the speakers and in a bigger and deeper soundstage for a start. On one track the music ended but the tapes were still rolling for about 15 seconds and I was very aware of the acoustic of the room even though the music had died out.. if you know what I mean?

Dynamics seem more effortless. Not more dynamic, but more a case of it sounding less forced and more "real". This, combined with the great soundstaging, makes for a much "bigger" overall sound that sounds more organic and less like a hi fi...

Maybe the valve pre is "adding niceness" or maybe it's acting as an RF filter? I'm enjoying what I'm hearing so far though, although it's early days in my listening tests so these are preliminary findings;)

Removes 6Moons head.... :D

I reckon anyone knocking up one of these will be very happy with it :)

[struth]

I like knocking some things up

[Radford Revival]

Thanks for the suggestion Will:) I actually had considered that and dug out a packet of little T092 SCR's but found that with a "BT47" style relay it reacts well to the slowly rising voltage and switches clean enough for there to be the click one would hope for from the relay, which surprised me! The Darlington does saturate nicely BTW when the cap is fully charged. I've kept my heaters AC on mine and on the diagram and made the smoothing cap small for the delay board so it drops the relay out nice and quick when power is removed... I could probably get away with raw DC but added a bit of smoothing to keep things electrically quiet.

It's just a pity that my decision to use a non cathode follower topology, for a host of reasons, has meant having to deal with a rather large switch on thump.... we're talking 100V!:eek: And SS amps don't like that up 'em Mr Mainwaring:D

Indeed, the ramp up isn't necessarily a problem at all - I just remember thinking of the SCR after making the PCB and kicking myself :D

[Arkless Electronics]

Indeed, the ramp up isn't necessarily a problem at all - I just remember thinking of the SCR after making the PCB and kicking myself :D

In testing, an LED did of course come on VERY gradually!

[Arkless Electronics]

"Live at Blues Alley" Eva Cassidy now..... nice:eyebrows:

[JohnJo]

Very interesting Jez, I have just been trying a simple single valve linestage and comparing it to my passive and my conclusions are exactly the same as yours; better soundstage and musical flow but a slight loss of transient edge which seems to ever so slightly blunt rhythms. The top end sweetness works well with coarser material but there's a resolution with the passive that's addictive. I'm guessing to have your cake and eat it means a very expensive active pre. I assume the upgrade path is a heavily spec'd power supply?

[Radford Revival]

How about something like this as a "plus" or "advance" version (for those with lower impedance needs):

http://i.imgur.com/2axBZ3E.gif

Reason for not DC coupling the 2nd stage: Allows independent / optimal biasing of 2nd stage, no DC surge through grid protection diode!

[Arkless Electronics]

How about something like this as a "plus" or "advance" version:

http://i.imgur.com/2axBZ3E.gif

Reason for not DC coupling the 2nd stage: Allows independent / optimal biasing of 2nd stage, no DC surge through grid protection diode!

Your an LT switcher CAD man eh... Works great but I love the user friendliness of Multisim;) Yes, nice, and gets rid of need for compulsory switch on delay, but... The feedback combined with moderate anode resistance and nice slope of the ECC88 allows an output impedance of 500R, with the ability to drive 10K loads to several Volts at low distortion, already, and for less components in the signal path;) Measured performance re THD etc would be roughly the same. I'd put stoppers of 33R or so on U2 grid and at output to kill any sproggies there BTW... You probably just left them out for ease of reading the diagram of course.

I have other ideas for a "plus" version:eyebrows: I may well make a version of this for sale as well... This was not the intention but it sounds so nice! There's just enough valveyness to make you guess it's probably not SS... but not obviously, and with loads of grip and well... "focus" to the sound, if that makes any sense?

It could be dangerous for neighbour relations as it makes you want to turn it up really loud 'cos there's no sense of "strain" or "edge" to make you think "that's loud!"

[Arkless Electronics]

Very interesting Jez, I have just been trying a simple single valve linestage and comparing it to my passive and my conclusions are exactly the same as yours; better soundstage and musical flow but a slight loss of transient edge which seems to ever so slightly blunt rhythms. The top end sweetness works well with coarser material but there's a resolution with the passive that's addictive. I'm guessing to have your cake and eat it means a very expensive active pre. I assume the upgrade path is a heavily spec'd power supply?

Actually, no... although improvements are possible on that front of course;)

[JohnJo]

Actually, no... although improvements are possible on that front of course;)

OK, that seems to be the route with the Croft stuff as the price rises, regulated supplies.

[Radford Revival]

Your an LT switcher CAD man eh... Works great but I love the user friendliness of Multisim;)

I've always quite liked LTspice, I've never actually tried multisim, I may have to give it a go. Either certainly cut down on a lot of development time, I'm a big fan of simulation given an understanding of the limitations.

[Arkless Electronics]

I've always quite liked LTspice, I've never actually tried multisim, I may have to give it a go. Either certainly cut down on a lot of development time, I'm a big fan of simulation given an understanding of the limitations.

Yeah it's a real boon but as you say one must be very aware of it's limitations, especially around accuracy of component models! If one doesn't know enough about electronics to "smell a rat" it can lead you right up the garden path as they say...
Multisim has vastly bigger component libraries than LT Spice (and they aren't mainly LT's own products) and, best of all, virtual instruments!

[Arkless Electronics]

OK, that seems to be the route with the Croft stuff as the price rises, regulated supplies.

As I say it's one option but probably not the first in this case. I'm not going to take it up to any higher level for the moment. It's already very good indeed! I suggest builders leave enough space for future upgrades though (hint);)
Tag strip and point to point wiring is fine for construction as is any other method. It will sound the same however it is built provided the most important area, correct grounding, is adhered to. Getting grounding wrong is probably the biggest mistake noobs make, along with bad soldering and (linked to the first point) trying to make it look neat rather than correct ;)

[Arkless Electronics]

No interest then... oh well it rekindled my interest in active line stages and resulted in my decision to include an active line amp in my latest forthcoming product :)

[CornishPasty]

Jez, I'm going to have a go at this in a couple of weeks when I've some breathing space. I already have a Chinese preamp that looks ace but sounds crap which will be the donor. It has a decent psu with 6X4 rectifier. I paid 300 quid for it and its utter shite. It's time it was reborn.

[Colin Wonfor]

Here's the final thing. There are a few minor changes here and there...

http://i1303.photobucket.com/albums/ag156/Jez1235/DIY%20pre%20for%20AOS%203-9-16%20with%20PS%20_001_zpsb9oiwaon.jpg (http://s1303.photobucket.com/user/Jez1235/media/DIY%20pre%20for%20AOS%203-9-16%20with%20PS%20_001_zpsb9oiwaon.jpg.html)

Bizarrely there is no suitable relay in my CAD software so the relay coil is shown as a 1mH choke and the normally closed contacts as two separate switches.

I'll leave this as job done and post no more now on construction etc until/unless anyone wants to build one and needs any assistance;)

I could if you like do a layout with relays etc on a PCB and supply Gerber files if you like. On single sided PCB with the correct track clearance and star earthing.

[martian sunrise]

I'd love to have a go at this but wouldn't know where to start.

[Arkless Electronics]

I could if you like do a layout with relays etc on a PCB and supply Gerber files if you like. On single sided PCB with the correct track clearance and star earthing.

You must have too much time on your hands Colin!:) Yeah why not... it would I'm sure make things vastly easier for beginners to have a PCB with silk screened component designators:)

[Colin Wonfor]

It will be fitted in the 3AM shift :)

[Arkless Electronics]

It will be fitted in the 3AM shift :)

I'm not the only one who sometimes works at those sort of hours then....:)

[Brumjam]

This looks really interesting Jez. I've always been put off building anything with valves due to the circuit complexity and my lack of knowledge. If Colin kindly provides the files for PCB's that makes it even easier. We can get a batch of pcb's produced if there's enough interest.

I'll get a cheapo case and the peripheral bits ordered in the meantime.

[CornishPasty]

I'll do mine point to point as the tube(s) lie flat. The muting circuit would be fine on a pcb as that's solid state. If the intention is to put it all on one board then it's no issue, I'll just leave it out. None of my other pre's have it and I've had no problems in the past forty odd years.

[Arkless Electronics]

I'll do mine point to point as the tube(s) lie flat. The muting circuit would be fine on a pcb as that's solid state. If the intention is to put it all on one board then it's no issue, I'll just leave it out. None of my other pre's have it and I've had no problems in the past forty odd years.

I'm sure a pulse of 150 Volts couldn't possibly damage a power amp..... You should be ok if using only valve power amps but if using any SS power amps then I'd put the mute circuit in;)

Point to point or PCB won't make any difference to the sound...

[CornishPasty]

I have a choice of valve or SS power amps in my system but have a strict policy of switching on all the ancillary equipment first and then the amps after a couple of minutes. Switch off is a reversal of the regime. I do appreciate what your saying though Jez.

I read earlier a post by Barry about paralleling the two halves of the valve. Are there any benefits to this or any downsides?

[martian sunrise]

I am keen to have a go at this and would be interested in a PCB if a run were made.

What are the expensive parts going to be? Is it possible to build a 'prototype' with the cheapest bits available, using say one of the eBay electronics kits, then put together the real deal once I have had a practice and better understanding. Or is that a waste of time/cash?

Also, if there was a parts list, could you recommend options for good/best components?

[Arkless Electronics]

I have a choice of valve or SS power amps in my system but have a strict policy of switching on all the ancillary equipment first and then the amps after a couple of minutes. Switch off is a reversal of the regime. I do appreciate what your saying though Jez.

I read earlier a post by Barry about paralleling the two halves of the valve. Are there any benefits to this or any downsides?

Whilst that is always the recommended regime it won't prevent the possibility of damage in this case. A pulse of 150V or more will still go to the input of a power amp whether or not it is switched on. In a more conventional cathode follower the output voltage starts at zero and ramps up slowly as the valve warms up, slow enough that the output capacitor will block the slowly rising DC. This topology does the exact opposite. Without the two Zeners the output goes immediately to 300V or more and then ramps down to zero (via the capacitor). Even with the Zeners it goes to 150V. Destruction of a SS power amp is likely without the mute circuitry. If using valve rectifier then you could get away without the mute circuitry as the voltage ramps up slowly as the valve rectifier warms up.

Advantages of paralleling both halves of the valve are half the output impedance and twice the ability to drive low impedance loads. It is more than adequate already though in these areas so whether or not it sounds any better is a "suck it and see" thing! Down sides are tenuous so not worth bothering with....

[Arkless Electronics]

I am keen to have a go at this and would be interested in a PCB if a run were made.

What are the expensive parts going to be? Is it possible to build a 'prototype' with the cheapest bits available, using say one of the eBay electronics kits, then put together the real deal once I have had a practice and better understanding. Or is that a waste of time/cash?

Also, if there was a parts list, could you recommend options for good/best components?

The most expensive part, potentially, as always is the case. There is lots of leeway here of course! I put a link earlier in the thread to a suitable toroidal transformer for it at about £30. I wouldn't change from that transformer if I was you;) Other than that you can use whatever you like to build it. Bear in mind that some of the resistors are 2W rating. Polypropylene output capacitors should be used for best sound but will be pricey compared to electrolytics (£5-10 compared to 70p or so). Electrolytics can of course be used to get you away....

I wouldn't bother with ebay kits... you'll probably end up with more trouble than it solves!

My best tip is use the correct mains transformer I specified, for a number of reasons.. oh and be sure to use strict star grounding! Colin is going to put this into the PCB so that is taken care of for those that want to use the PCB route.

[RothwellAudio]

I assume the upgrade path is a heavily spec'd power supply?


Actually, no... although improvements are possible on that front of course;)

A good power supply is always a good idea. Unfortunately, too many consumers equate a good power supply with a huge transformer and huge reservoir capacitors - hey, they're big, they're expensive, they must be better, right? I've given up arguing :doh:

[Arkless Electronics]

A good power supply is always a good idea. Unfortunately, too many consumers equate a good power supply with a huge transformer and huge reservoir capacitors - hey, they're big, they're expensive, they must be better, right? I've given up arguing :doh:

I think we're preaching from the same hymn book Andrew!! That's twice today you've said total sense which I've 100% agreed with:)

Yeah try telling them that everything they think they know about power supplies is wrong and the important bit is the regulation or R/C filtering at point of load....

It is really frustrating that the industry, realising that most have no electronics knowledge, has built up all sorts of myths which are generally regarded as gospel by enthusiasts but which are 100% wrong... and usually centre on big/heavy/shiny/recommended by so and so/contains precious metals or pro biotic vitamins or pixie dust....

All sorts of important fundamentals are completely ignored because they require technical knowledge... whilst things which have no/little effect but can be fitted by a lay person will get threads going on for pages... :doh: I give up....

[Marra]

This looks really interesting Jez. I've always been put off building anything with valves due to the circuit complexity and my lack of knowledge. If Colin kindly provides the files for PCB's that makes it even easier. We can get a batch of pcb's produced if there's enough interest.

I'll get a cheapo case and the peripheral bits ordered in the meantime.

+1 for a circuit board build. I've never had the confidence for point to point.

[RothwellAudio]

Yeah try telling them that everything they think they know about power supplies is wrong and the important bit is the regulation or R/C filtering at point of load....


Regulation? What's that? Can I have my regulation made with silver wire? Solid core, of course :)

Actually, sometimes I think I'm an idiot - wouldn't it be simpler just to give people what they want? I have a box full of very old capacitors and I've contemplated selling them off one at a time on ebay to the guitarists who must have a "bumble bee" or "tropical fish" capacitor for authentic vintage tone. But then I'd feel like I've taken advantage of them.

[Marco]

No issues with Andrew talking perfect sense. However:


All sorts of important fundamentals are completely ignored because they require technical knowledge... whilst things which have no/little effect but can be fitted by a lay person will get threads going on for pages... :doh: I give up....

As the forum is made up of 90% 'laymen', not electronics engineers, it's hardly surprising that the things we can do, which to our ears make a difference, is what gets talked about! ;)

Also, don't forget that it's the 'laymen' who buy your products and thus pay your wages........

Marco.

[Colin Wonfor]

Is the transformer or transformers on the PCB and what size?

[Colin Wonfor]

Having checked the datasheet for the ECC88 it seems it's rated up to 550V cold so we can lose the Zener diodes:) here's the amended diagram.

http://i1303.photobucket.com/albums/ag156/Jez1235/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_001_zpsxoodajhb.jpg (http://s1303.photobucket.com/user/Jez1235/media/DIY%20pre%20for%20AOS%203-9-16%20with%20PSU_001_zpsxoodajhb.jpg.html)

I'd only put them in as safety precaution but as it's safe to get rid that is a good thing!

Do you need a delayed on controlled by the heater time to switch on HT? And a heater and HT warning LED?

[Arkless Electronics]

No issues with Andrew talking perfect sense. However:



As the forum is made up of 90% 'laymen', not electronics engineers, it's hardly surprising that the things we can do, which to our ears make a difference, is what gets talked about! ;)

Marco.

Indeed. As an EE though I find that things which are REALLY important and can make massive changes get completely ignored by people cos they don't understand them... a bit like the person putting their fingers in their ears and shouting "la, la, la, la," etc... they then obsess with things they CAN do themselves but which are of little or no use/improvement....
I've used the metaphor before of people into cars but who don't understand the fuel injection system or valve timing (which of course can make a huge difference to performance) and so obsess with things like tyres with 0.01% less rolling resistance or light weight seat covers or whatever....

Anyway if everyone could do their own electronic engineering there would be no work for us EE's:D

[Arkless Electronics]

Is the transformer or transformers on the PCB and what size?

Better I think to keep it off the pcb. There is a link earlier in the thread to a suitable toroidal transformer of 30VA.

[Colin Wonfor]

Better I think to keep it off the pcb. There is a link earlier in the thread to a suitable toroidal transformer of 30VA.

I will leave space on PCB for some to fix it too.

[Marco]

Indeed. As an EE though I find that things which are REALLY important and can make massive changes get completely ignored by people cos they don't understand them...

But that's just natural, surely, and not any form of criticism?

I'm a music lover and hi-fi enthusiast, so all I care about is how my gear SOUNDS. Beyond the necessary basics, I have no interest whatsoever in learning how equipment works or how to build it, the same as I have no interest in how my TV or washing machine works, or how to build those - they're just products that I use. Why should I behave differently?

Therefore, you can hardly expect folk to discuss what they don't know....

You have to accept, Jez, that not everyone's mind works the same way, and so there will always be both end-users of products, and those who design them - and BOTH sets of people are of equal importance and necessary to make the world go round! ;)

Marco.

[Arkless Electronics]

Do you need a delayed on controlled by the heater time to switch on HT? And a heater and HT warning LED?

No point in overcomplicating it.... the delay of the mute circuity keeps the output shorted until the heaters have warmed up etc anyway. I've used the Zeners in my unit but just to keep the capacitors a bit cheaper as 160V rated ones can then be used. I guess most building this will not be bothered by saving a few quid on the output caps but I only had 250V parts to hand and without the Zeners the output cap will see about 340V whilst the valve warms up of course.

Cheers for taking on the PCB BTW Colin:) It's one of those tasks I relish as much as cleaning the oven so I only do it if I have to! At my last "proper job" I used to take on all the most challenging R&D jobs... so someone else would get lumbered with designing the PCB's! It took them ages to suss my ploy:eyebrows:

[The Black Adder]

Have you a pic of it, Jez?

[Arkless Electronics]

But that's just natural, surely, and not any form of criticism?

I'm a music lover and hi-fi enthusiast, so all I care about is how my gear SOUNDS. Beyond the necessary basics, I have no interest whatsoever in learning how equipment works or how to build it, the same as I have no interest in how my TV or washing machine works, or how to build those - they're just products that I use. Why should I behave differently?

Therefore, you can hardly expect folk to discuss what they don't know....

You have to accept, Jez, that not everyone's mind works the same way, and so there will always be both end-users of products, and those who design them - and BOTH sets of people are of equal importance and necessary to make the world go round! ;)

Marco.

Well yes it's bound to be that way to quite some extent. As you say I, as an EE and designer, see things very differently to the average end user!

I wrote a lot more but deleted it as my "circular argument" and "likely to cause offence by speaking the truth" warning lights came on:D

[Marco]

Ha....

You mean likely to cause offence by expressing merely your valid opinion... When it comes to subjective matters in audio, there are few indisputable "truths" spoken; merely collections of opinions expressed, and yes, best we leave it there! ;)

Marco.

[Arkless Electronics]

Have you a pic of it, Jez?

Hmmm ... strange question! It's a diy thing so will look like whatever each builder of it wants it to I guess! There is a pic of my lash up for testing purposes in post 52 but I fail to see its relevance personally:) It could look like my lash up or be built in a super duper gold plated half inch thick case depending on the builders preferences!

I can report that it sounds VERY good! So good that with some power supply improvements it's the same circuitry I'm using for the line stage of my new pre amp!

I will probably experiment with further improvements for the latter but it sounds so good there seems little point really...

[Arkless Electronics]

Ha....

You mean likely to cause offence by expressing merely your valid opinion... When it comes to subjective matters in audio, there are few indisputable "truths"; merely collections of opinions, and yes, best we leave it there! ;)

Marco.

Well that's one area where we are chalk and cheese Marco.... Yes I think certain things in audio are 100% certainly right or wrong whilst you think they are only my opinions... so yes best we leave it there:)

[Marco]

When it comes to SUBJECTIVE matters in audio, which is what we were discussing earlier in another thread about speaker baffles [as there is no 'right' or 'wrong' in loudspeaker design], by its very nature, the vast majority of it is simply opinion, not fact. You can't really argue with that - and if you'd wanted to leave it there, Jez, you could've done so without further responding.

Don't insist on having the LAST word, as that will always be a luxury reserved for me! ;)

Marco.

[RothwellAudio]

+1 for a circuit board build. I've never had the confidence for point to point.

Point-to-point wiring can get complicated where the circuit is complicated but this design is so simple that it's an ideal introduction to point-to-point wiring. Generally speaking I find the hardest part of one-off or custom builds is the casework, but there is a way round that - buy something cheap off ebay. There are some cheap Chinese preamps on ebay that cost less than it would cost to buy the parts in the UK, so it's worth considering getting one of those to re-wire. There are probably lots of suitable empty cases on ebay too, already punched-out for valve bases and sockets etc.
BTW, one of the big advantages of point-to-point wiring is it's so easy to make modifications.
Also, I should mention that I like the design of this preamp. All too often I see circuits for DIY preamps which have one major flaw - far too much gain. This design has 10dB, which I consider ideal. Its input impedance isn't particularly high, but it's plenty high enough, and the output impedance is plenty low enough too. I approve :)

[Colin Wonfor]

http://seca.freeforums.net/attachment/download/37

http://seca.freeforums.net/attachment/download/36

Gerber file down load here :-TUBE DIY - CADCAM.ZIP (354.3 KB) http://seca.freeforums.net/thread/29/ecc88


OK now have fun.

[Colin Wonfor]

Any comments?

Are you having trouble downloading the Gerber file?

Ok I will delete them and put them up a fresh.

Refresh page :-

[Marco]

Hi Colin,

I've just read your comments 'elsewhere' in relation to the above file you kindly provided for our DIY-minded members to use for their projects, and which you've now removed out of disappointment.

Whilst you should've been thanked for your generous act, and I completely sympathise with your feelings because you weren't , I'm afraid, sadly, that's just human nature and indicative of the kind of world we now live in.

As a Christian, in reference to selflessness, I'm reminded of the following, which you may wish to consider, particularly the last sentence:

[I]"One trait that is needed on your Christian walk of faith is selflessness. Sometimes we worry about ourselves and our wants rather than wanting to give others our time and our help, but this should not be. We must have empathy for others and put ourselves in someone else’s shoes. The only thing this selfish world cares about is what is in it for me? We don’t need a reason to serve and help others, we just do and we do it expecting nothing in return."

Think about that, and if you do decide to help others again, *do it* because you're one of the good guys, and set an example of how others should behave in this selfish world we live in today, not because you're seeking any thanks.

I say that, mate, out of the best of intentions and respect for you, and so hope you take it that way. You're a valued member here, and I don't want to see you discouraged from posting your pearls of wisdom! :)

Marco.

[Colin Wonfor]

Thanks Marco,

I find it so frustrating as I spent a few hours of time doing what I thought was a good deed just to be used as if I was a paper tissue and just taken for granted. It has taken me many years to learn the things I do and now my time is limited to be treated this way makes me mad and brings back shit memories of my resent past. Now I am on this PC and not the other one I can a will put this project back up.
As to being a christian I lost faith in a god when my Jenny was taken away from me in 1990 in a car crash on our Honeymoon, so I suspect God has moved on to better things than the creature on this planet.

Thanks for the msg.

[Marco]

No worries, mate. Always look on the bright side of life :)

Marco.

[Colin Wonfor]

http://seca.freeforums.net/attachment/download/39

http://seca.freeforums.net/attachment/download/40

http://seca.freeforums.net/thread/30/diy-arkless-tube-amp

[Marco]

Images aren't working for me, mate....

Marco.

[RothwellAudio]

It's possible that Colin's efforts didn't go unappreciated, just that very few members on the forum would know what to do with a gerber file.

[Marra]

It's possible that Colin's efforts didn't go unappreciated, just that very few members on the forum would know what to do with a gerber file.

I would count myself amongst that group.
I very much appreciate Col doing this and would be interested in a pcb were someone to organise a group buy.

[Marco]

It's possible that Colin's efforts didn't go unappreciated, just that very few members on the forum would know what to do with a gerber file.

I have to admit, I'd never even heard if it... :eyebrows:

So I think you have a valid point, Andrew. That's the trouble sometimes with those who are technically minded; there's a tendency to 'presume' that everyone else is on the same level, and so automatically understands what they understand.

That's not a slight on Colin, as he's not the only 'techy' guilty of that. The tendency is to talk in a different language. When giving advice/tips like this, I always think it's best to assume that one's audience has the knowledge of a layman, and then take it from there :)

Marco.

[martian sunrise]

I would count myself amongst that group.
I very much appreciate Col doing this and would be interested in a pcb were someone to organise a group buy.
+1

[Arkless Electronics]

Just seen this.... I'm sure no one is unappreciative of Colins efforts and it is more the fact that it's a Gerber file as someone said, plus I for one can't access them so I'm sure others are having the same problem. I get a message about not having permission to download images or some such when trying to see them. I can only see the thumbnails.

[Colin Wonfor]

Just download Gerber Zip file take it or send it to a PCB manufacture and he can print the PCB,s

We us this one:-

Blackwater Photographic Company Limited
Unit 6;Redfields Industrial Park
GU52 0RD
Church Crookham
Hampshire England
Phone: 01252 613243

There are lots or try this lot:- http://www.pcbtrain.co.uk/

[Colin Wonfor]

Just click on the TUBE DIY - CADCAM.ZIP (354.3 KB) and save.

On linked site not this one.

But this site: - http://seca.freeforums.net/thread/30/diy-arkless-tube-amp

[Arkless Electronics]

I get the following message "Guests do not have access to download attachments. Please log in and try again"

[RothwellAudio]

Just download Gerber Zip file take it or send it to a PCB manufacture and he can print the PCB,s

We us this one:-

Blackwater Photographic Company Limited
Unit 6;Redfields Industrial Park
GU52 0RD
Church Crookham
Hampshire England
Phone: 01252 613243

There are lots or try this lot:- http://www.pcbtrain.co.uk/

Will they make just one? They place I normally use charge for tooling and the minimum cost is well into the hundreds of pounds. That's fine for me but less than ideal for a DIYer.
I know there are places that will make very small quantities (or one-offs) but I've never used them.

[Colin Wonfor]

Marco.

Can you download or have attachments on this forum?
Can send the Gerber files to a store place here?
Or will you site take it as TXT and would folk be able to convert to a good Gerber file?

For example this is Bottom Copper file called " CADCAM Bottom Copper"

G04 PROTEUS RS274X GERBER FILE*
%FSLAX24Y24*%
%MOIN*%
%ADD21C,0.0800*%
%ADD22C,0.1000*%
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%ADD26C,0.0400*%
%ADD27C,0.0013*%
%ADD28C,0.0100*%
%ADD10C,0.2952*%
%AMDIL001*4,1,8,-0.0450,0.0820,
-0.0270,0.1000,0.0270,0.1000,0.0450,0.0820,0.0450,-0.0820,
0.0270,-0.1000,-0.0270,-0.1000,-0.0450,-0.0820,-0.0450,0.0820,0*
*%
%ADD11DIL001*%
%AMDIL002*4,1,8,-0.1000,0.0270,
-0.0820,0.0450,0.0820,0.0450,0.1000,0.0270,0.1000,-0.0270,
0.0820,-0.0450,-0.0820,-0.0450,-0.1000,-0.0270,-0.1000,0.0270,0*
*%
%ADD12DIL002*%
%ADD13C,0.1500*%
%ADD14C,0.0900*%
%ADD15C,0.1000*%
%AMDIL006*4,1,8,-0.0750,0.0300,
-0.0550,0.0500,0.0550,0.0500,0.0750,0.0300,0.0750,-0.0300,
0.0550,-0.0500,-0.0550,-0.0500,-0.0750,-0.0300,-0.0750,0.0300,0*
*%
%ADD16DIL006*%
%ADD17C,0.1200*%
%ADD29C,0.0157*%
%ADD18C,0.0800*%
%ADD19C,0.1400*%
%AMDIL010*4,1,8,-0.0300,0.0330,
-0.0180,0.0450,0.0180,0.0450,0.0300,0.0330,0.0300,-0.0330,
0.0180,-0.0450,-0.0180,-0.0450,-0.0300,-0.0330,-0.0300,0.0330,0*
*%
%ADD70DIL010*%
%ADD71C,0.1696*%
%ADD20C,0.0080*%
G54D21*
X+32200Y+16966D02*
X+32200Y+431D01*
X+27522Y+16966D02*
X+27522Y+13478D01*
X+27334Y+13289D01*
X+27522Y+13226D01*
X+27522Y+4564D02*
X+27522Y+431D01*
G54D22*
X+618Y+7580D02*
X+9125Y+7580D01*
X+9613Y+7092D01*
X+9477Y+7186D01*
X-3381Y+5611D02*
X-3381Y+7580D01*
X-3318Y+2462D02*
X+65Y+2462D01*
X+602Y+2999D01*
X+602Y+5499D01*
X+767Y+5663D01*
X+618Y+5611D01*
X+618Y-3049D02*
X+618Y-1081D01*
X+5343Y+2462D02*
X+9186Y+2462D01*
X+9256Y+2531D01*
X+9477Y+2509D01*
X+28Y+856D02*
X+932Y+856D01*
X+2223Y+2147D01*
X+2223Y+5975D01*
X+618Y+7580D01*
X-5877Y+2462D02*
X-4068Y+2462D01*
X-3381Y+2462D01*
G54D23*
X-3318Y+2462D01*
G54D22*
X-3381Y-1081D02*
X-3381Y+2462D01*

[Arkless Electronics]

Certainly £150 ish anyway and possibly more. It will need to be a group buy if people want to go the PCB route...

It's SO simple though that other construction methods can of course easily be used. They will not effect the sound so long as grounding and layout are fine.

[Colin Wonfor]

The silk screen top layer will not fit 14M character T.A.O.S. as a txt file complains.

[RothwellAudio]

Certainly £150 ish anyway and possibly more. It will need to be a group buy if people want to go the PCB route...

It's SO simple though that other construction methods can of course easily be used. They will not effect the sound so long as grounding and layout are fine.
I agree that the circuit is ideal for point-to-point or tagstrip construction. A few pictures or diagrams to get people started and give them confidence is probably a good idea.

[karma67]

thanks for the link to this thread jez,the trouble is as a novice i may be able to recap crossovers but,as a few have already said the technical terms and the wiring diagram go right over my head :(
also what is the purpose of this if you already have an amp please?

[Arkless Electronics]

thanks for the link to this thread jez,the trouble is as a novice i may be able to recap crossovers but,as a few have already said the technical terms and the wiring diagram go right over my head :(
also what is the purpose of this if you already have an amp please?

Non I guess.... it was just a much simpler diy project... about 100 x simpler than the phono stage you wanted to build!

[Brumjam]

Jez, I'm going to start asking some novice questions about the circuit diagram. This will be the first time I've built something using a diagram instead of using a PCB (assuming there's no cheap route to producing Colin's gerber file).

Novice question 1: Should there be one star ground point per channel? Or can all ground wires for both channels run to a single point?

[Arkless Electronics]

Jez, I'm going to start asking some novice questions about the circuit diagram. This will be the first time I've built something using a diagram instead of using a PCB (assuming there's no cheap route to producing Colin's gerber file).

Novice question 1: Should there be one star ground point per channel? Or can all ground wires for both channels run to a single point?

One single point is best. You can get (or could....) star ground washer/tab/lug things (probably a name for them somewhere!) where a lock washer has solder tags coming of it in star fish stylee which will probably help.
Everything that connects to ground should go to this. And I mean everything! Do not even ground the phono sockets to the chassis as a short cut for example.... Thats why most of them come with insulating washers to prevent contact with chassis;)

[Colin Wonfor]

The only problem I see in doing point to point is most folk will not have the experience of (A) doing it and (B)) no idea on voltage clearances and safety at 400+VDC, and that does concern me as I will miss some of you nutters and smoke is always a worry.

[Brumjam]

One single point is best. You can get (or could....) star ground washer/tab/lug things (probably a name for them somewhere!) where a lock washer has solder tags coming of it in star fish stylee which will probably help.
Everything that connects to ground should go to this. And I mean everything! Do not even ground the phono sockets to the chassis as a short cut for example.... Thats why most of them come with insulating washers to prevent contact with chassis;)

Thanks Jez. I've been there and got the t-shirt re not insulating phono sockets from the chassis :)

[Arkless Electronics]

The only problem I see in doing point to point is most folk will not have the experience of (A) doing it and (B)) no idea on voltage clearances and safety at 400+VDC, and that does concern me as I will miss some of you nutters and smoke is always a worry.

No DIY project can be completely safe as you can't prevent idiocy! If people stick fingers in whilst it's switched on well there are awards for them... Darwin Awards!
They can also still put electrolytics and diodes in the wrong way round even with a PCB with a silk screened layer, though it is more difficult as usually the correct orientation is printed on the PCB.

[Arkless Electronics]

http://uk.rs-online.com/web/p/barrier-strips/0433775

http://uk.farnell.com/ettinger/19-05-745/solder-eyelet-3x-angled-id-4-3mm/dp/1336213

http://uk.farnell.com/duratool/d01502/ground-terminal-brass-np-l-21/dp/1733434

The way I recommend is to put a length of the terminal strip on either side of the valve socket and build it like that. This is the easiest way unless you want to go the PCB route.
The best I could find re ground lugs is also in the link above but you can get ones which go around 360 degrees and it these you should ideally use. It probably won't be possible to get any so then just use several of the normal ones one on top of the other arranged like a star fish and VERY TIGHTLY bolted together.

If not using the PCB route then you will need to add the input switching, sockets vol control etc wiring. I assume these are all on the one PCB Colin did but as I can't open the files I don't know...

[Arkless Electronics]

I will put together a parts list with part numbers from Farnell or RS before long.... All parts are non critical and any equivalent part will do fine ie if I say "C12- 22uF 250v RS number 345-678" then any other 22uF 250V cap which will physically fit should do just fine... it doesn't matter what brand it is but does matter that it is the right value and voltage rating!
As nothing more has come of the PCB I'll assume point to point wiring with tag strip as the method of construction but any method will work as well as any other provided grounding and layout are OK.
Whilst this is eminently suitable as a first DIY project you will need to be able to read a circuit diagram.

[sq225917]

For the phono sockets I thought best practice was a 1n ceramic cap straight to the chassis, literally straight off the body of the socket to the nearest point. I can dig the article out, guy tries a load of options, star ground, T ground between the caps, combo of the two and all the other popular variants. He measures them all, shows the results. The differences are in the uV but they are utterly consistent. With cap to chassis being better for HF noise coming in on the rca cable.

[Arkless Electronics]

For the phono sockets I thought best practice was a 1n ceramic cap straight to the chassis, literally straight off the body of the socket to the nearest point. I can dig the article out, guy tries a load of options, star ground, T ground between the caps, combo of the two and all the other popular variants. He measures them all, shows the results. The differences are in the uV but they are utterly consistent. With cap to chassis being better for HF noise coming in on the rca cable.

You'll have to explain a bit more as to what you mean here Si... I'm not with you as to how you are connecting the earth's here.... Minimum RF ingress is not what I'm going for though. Maximum simplicity is.
Preventing RF ingress is a huge subject on its own and doing it successfully over the full bandwidth of potential interference sources pretty much impossible in practice. RFI on actual signal lines is a case in point.... one may want the audio bandwidth to extend to 100KHz or more, however. there are long wave radio stations not much higher than that.... try removing the RFI without compromising the signal you do want;)
At the other end of the spectrum even fairly small holes or gaps in a case will destroy any attempts to have a Faraday Cage. RF gear at UHF+ will often have what seems like a silly quantity of fixing screws holding the lid on... like one every half inch in some cases. This is because this practice is necessary to be sure of no RF getting in or out at GHz type frequencies.

We are in an age of unprecedented RFI due to mobile phones and wi-fi, if I am using my head amp (the battery powered one in the plastic case) then I have to switch my wi-fi off as the only place I can put the head amp is about 2 foot from the wi-fi transmitter! It has built in protection against RFI but it's not enough to deal with the wi-fi being that close so it's switch off the wi-fi or wrap the head amp in tin foil completely... the latter works.

[Arkless Electronics]

Well here's that BOM!

http://i1303.photobucket.com/albums/ag156/Jez1235/AOS%20DIY%20pre%20BOM_001_zpsttxy1ccy.jpg (http://s1303.photobucket.com/user/Jez1235/media/AOS%20DIY%20pre%20BOM_001_zpsttxy1ccy.jpg.html)

http://i1303.photobucket.com/albums/ag156/Jez1235/AOS%20DIY%20pre%20BOM_002_zpsiolow9rg.jpg (http://s1303.photobucket.com/user/Jez1235/media/AOS%20DIY%20pre%20BOM_002_zpsiolow9rg.jpg.html)

http://i1303.photobucket.com/albums/ag156/Jez1235/AOS%20DIY%20pre%20BOM_003_zpsomf5pmia.jpg (http://s1303.photobucket.com/user/Jez1235/media/AOS%20DIY%20pre%20BOM_003_zpsomf5pmia.jpg.html)

http://i1303.photobucket.com/albums/ag156/Jez1235/AOS%20DIY%20pre%20BOM_004_zpskhq3itoz.jpg (http://s1303.photobucket.com/user/Jez1235/media/AOS%20DIY%20pre%20BOM_004_zpskhq3itoz.jpg.html)

http://i1303.photobucket.com/albums/ag156/Jez1235/AOS%20DIY%20pre%20BOM_005_zps3rdkji8o.jpg (http://s1303.photobucket.com/user/Jez1235/media/AOS%20DIY%20pre%20BOM_005_zps3rdkji8o.jpg.html)

A suitable mains transformer is shown in an earlier post and this is the one I recommend.

The above BOM does not include the valve itself, a case/chassis, IEC socket, on/off switch etc and presumes point to point construction on tag strip.
Feel free to use different vol control, sockets and source selector switch.

It comes to £53 so with the mains TX and chassis etc it should easy be doable within the £200 I guestimated early in the thread

[Arkless Electronics]

I'll add the switch on mute circuitry BOM later as it is more suited to veroboard construction...... ok I forgot:doh:

[Arkless Electronics]

Well as far as I'm concerned this is a dead thread now... If anyone should begin actually building one then I will help them but until/unless......

[Colin Wonfor]

It does seem sometimes the enthusiasm for one particular personal interest is wasted on others, others either have no time or interest in making anything except coffee whilst listening to MP3 crap.
That why all the good electronic mags have gone and mags involving selfie is the game.
Shame and this will be why the Chinese will rule the world , because we gave it to them.

[Arkless Electronics]

It does seem sometimes the enthusiasm for one particular personal interest is wasted on others, others either have no time or interest in making anything except coffee whilst listening to MP3 crap.
That why all the good electronic mags have gone and mags involving selfie is the game.
Shame and this will be why the Chinese will rule the world , because we gave it to them.

About right there Colin. Shame.

[CornishPasty]

I've already said I'll have a go at this as soon as I have some free time. I already have a donor preamp waiting to undergo surgery. Sorry Jez but you can't just expect people to drop what they're doing and jump to it.

[Arkless Electronics]

Over 12,500 members and 2 months since I started the thread.... 'nough said. Both myself and Colin have put some time and effort into this and one or two members may make one.. eventually.. apparently. If you do I'll give further help but other than that... I'm outta here...

[Bigman80]

I really fancy having a go at this Jez but I am lost at the diagram. Pointless even starting out. I do applaud your intention and willingness to share a free design though. Hopefully one day I can have a crack at it.

Sent from my EVA-L09 using Tapatalk

[karma67]

yep no point flogging a dead hose mate.