Pictures of my new phono pre-amp

Some pictures of my new phono pre-amp. The preamp itself is NAC102 phono boards in which I reaplaces some components, the regulators are ALW super regulators in which I replaced the pre-regulator by VBEs (see this thread for more info). The case is a metal case which I painted in beautiful black (can't really see it in the picture, need to touch it...).

So here is how it looks like:


and from the back


I mounted the four boards on another board on which I mounted the original NAC102 pins. Doing this allows me to quickly remove the phono boards for further modifications
Below this board I created a star to which I connected all the ground wires.


The phono boards has all the classic mods:
- Zener circuit removed
- BC128 for input/output
- 3.3uF SMR + 0.5R for decoupling
- Mil spec tantalum for feedback
- Other capacitors are polistyren where possible
- Some critical resistors replaced by WELWYN RC55Y (note that for some reason the feedback resistors in the NAC102 are 100K and 200K instead of 64K and 100K respectively). Here is how the phono boards look:


The regulators have a VBE instead of the tracking pre-regulator. This mod already sounds very good on the pre-amp boards, but here the improvement is really huge. It adds a very solid bass which was originally missing, and makes everything sound more natural and more detailed at the same time. Highly recommended here (and everywhere else...)!!!


BTW I remember that someone recently asked about replacing the resistors in the phono boards. Well, it adds some clarity but not day and night.

Yes, and last point, the PSU. With the VBE it's really not important which PSU you use, a single 32V rail from a HP deskjet does an excellent job, I compared it with a HiCap and couldn't hear any difference.

The sound of these boards is really splendid, I wish my CD would sound like this, well if fact I expect that once I install the PFM Flea and six APA627s in my CDX it will sound at least close to this...

I'm using an LP12/Lingo, LVX-III arm, with OC9 cartridge.

Teddy

A very neat job. Well done. I bet it sounds as good as it looks.

This is what I like to see, its about time more pictures of peoples diy work was posted
Anyway great job Teddy, very nicely done

Nice case too!

Hi Teddy,

What exact is the "3.3uF SRM + 0.5R for decoupling modification" in your MC-preamplifier? I don't find this modification anywhere described. Still another question: Where can I buy mil spec tantalum for feedback?

Thanks, Peter

It's a 3.3uF SMR capacitor (the white boxes), which are used for power decoupling instead of the original electrolytic.

mil spec tantalum caps are usually on ebay

Hi Teddy, to resurrect your thread/ fine phono stage here..

Re the psu: would any of these fit the bill below? if so, did you take such a thing apart & add a ~10,000uf cap/ rectifier sort of, or in short, how exactly did you use the HP psu? (Im trying to figure how one would implement such a psu to power one ALWSR for just the 322s- the 3 boards in situ in a 32.5).

http://search.ebay.co.uk/search/sea...=compare&copagenum=1&coentrypage=search&fgtp=

Cheers if you've a mo, Capt

Youre kidding? Is this a p***take?

Seriously though I presume you want to put at least 24V DC! out of the ALWSR? If so you will need a power supply in excess of 24V if it outputsDC.

You might add a cap.

Of the choices you showed on ebay I would go for

http://search.ebay.co.uk/HP-deskjet...fQQsargnZQ2d1QQsaslcZ3QQsbrftogZ1QQsofocusZbs

(maybe just finished)

Though personally I would go for a small AC adaptor, then put a good rectifier and cap in with the ALWSR. One of these (the 24V AC) and perhaps run the ALSWR and 322s at 26~28V (depending on input headroom) instead of 24V to give em some oomph ...

http://www.maplin.co.uk/module.aspx?ModuleNo=96964&doy=13m11

Im sure Teddy will be along to suggest a slightly better option certainly a Teddy style board is rumoured to work well with small (switching) power supplies, whereas an ALWSR may prefer a nice toroidal

Hope that helps until SuperTed arrives

ps I'll be doing similar soon, I want the boards close to the new deck ...

As mentioned/expected I'm not sure that an ALWSR would be the optimal solution after a noisy switch mode PSU, unless you have a VBE before/after it. But then comes the question, why do you need the ALWSR if the VBE does the work (or even better) and requires less dropout?

Martin Clark provides a very good description of the VBE effect after an SMPS in the acoustica site.

Teddy, have you replaced the tracking pre-regulator on your SRegs above with a VBE configuration? or are your VBEs underneath or elsewhere? Im confused trying to figure this approach above with a similar psu you mention, into one SReg for two 322s.

& when you say then there's no need for an SReg if the VBE does the work: are you implying you've effectively taken out your Sregs above now/ updated this design?

cheers Capt

In fact I've used the place on the phono boards where the original Naim VBE was to create a new VBE, then added another VBE for the front end. The SRs are still there but don't contribute much in this position given that they are followed by two VBEs.

I'll try to post pictures during the weekend.

Thanks Teddy any more pics would be very helpful- I realise most of the answer to my previous Q was in #1, rereading it.. v daft of me.

Cheers Capt.

Can I ask where your case is from? Looks ideal for the PSU I'm slowly building.

The Captain said:

Thanks Teddy any more pics would be very helpful- I realise most of the answer to my previous Q was in #1, rereading it.. v daft of me.

Cheers Capt.

Click to expand...

A bit late, but here it is

I'd appreciate info on a couple of points if you will Teddy as this is surprisingly like a project I have been working on for some time now, (right down to the 31V HP remote supply. These supplies are ridiculously cheap on eBay so why reinvent the wheel ). I still have a soft spot for a FET input to the classic Naim architecture, although it needs careful selection and set up with a much more individual approach.

Some critical resistors replaced by WELWYN RC55Y

Click to expand...

Come on now, cough up the goods, specifically which resistors on the phono board do you find respond usefully to replacement with RC55Ys? I still remain a little sceptical to the idea that any replacements will reap huge rewards, and it is refreshing to hear you say that a few are worthy of improvement.

And where did you get that case? It has the wonderful smell of a custom special, which gives it that little bit of extra stylish exclusivity. Really good job of mounting stuff into it too!.

The RC55Y is at most a minor improvement, I just felt that I *have* to do it...

I bought this case some years ago in the USA in a DIY store, it didn't look that good then, I painted it. Sorry if I dissapoint anyone but the quality of the case is less than optimal. I have to keep it far from any transformer otherwise I get hum.

Teddy

Sorry, I really should have said:

I still remain a little sceptical to the idea that just any old replacements will reap huge rewards, and it is refreshing to hear you say that a few are worthy of improvement.

Click to expand...

The stress makes it clear what I meant to say. I didn't mean "no" replacements were worthwhile.

teddy_pardo said:

The phono boards has all the classic mods:
- Zener circuit removed
- BC128 for input/output
- 3.3uF SMR + 0.5R for decoupling
- Mil spec tantalum for feedback
- Other capacitors are polistyren where possible
- Some critical resistors replaced by WELWYN RC55Y (note that for some reason the feedback resistors in the NAC102 are 100K and 200K instead of 64K and 100K respectively). Here is how the phono boards look:

Click to expand...

Teddy, bet you thought this one was well buried in the annals of time - but I just embarked on exploring the options for a better MC Stage solution than my 323/3s.

I like the look of this for simplicity but will base mine on 323 boards and probably make new ones from scratch. But I have a couple of questions::

1. Decoupling cap & resistors: Your text says 3.3SMR + 0.5R - yet the picture appears to show 2 10 Ohm resistors in parallel - for 5R. Or am I looking at the wrong thing?
2. How about a 10uF Wima here instead - easier to fit but what resistor value in series with it?
3. Why not use TeddyRegs in this application?

Everything else seems to be pretty straightforward.

Neil

1. It's two 1R resistors
2. They didn't exist at that time yet
3. Look at post #14 on this thread

teddy_pardo said:

1. It's two 1R resistors
2. They didn't exist at that time yet
3. Look at post #14 on this thread

Click to expand...

Wow thanks Teddy, that's fast.

1. I must be misreading the colour bands, I though it was a 5 band Br-Bla-Bla-Gold-Br - apologies for my poor eyesight.
2. So will 0.5 R work with the Wima too?
3. Oppps missed that - TeddyRegs in they go!