DIY Transistor Amp Using NVA Boards

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Paul Barker
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Re: DIY Transistor Amp Using NVA Boards

Post by Paul Barker » Sat Mar 31, 2018 9:06 am

Couple of weeks ago I was in Mexborough helping out a friend and had time to kill. No it was very last minute so I couldn't give Steve and Melanie warning, they're very kindly allowed me to go round and fall asleep on the sofa, feeding me with lunch plus healthy snacks. Monty seems to think I'm part of the family now.

I've been so overworked since Christmas that I can't give you a valid assessment. I can only give you personal impressions, I only heard the nva boards on that occasion and the speakers were different.

Bearing in mind my frame of mind was one of us heating engineer at the time of year when heating engineers and running on adrenal fatigue, and I was in the middle of an emotional social situation trying to help someone it would not had access to their children for six months, the Mercy mission was a great success. In spite of having all that going on in my head I could tell there was a quality to the nva boards. I could see both Stephen and Mel we're very happy which is the biggest impression to come away with. When you remove the egos the willy waving the obsessions, this is all that really matters if you have no business objectives in this game.

My personal tastes are on the side of the set. But what Steve was playing at day would satisfy me perfectly well.
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Re: DIY Transistor Amp Using NVA Boards

Post by Paul Barker » Sat Mar 31, 2018 9:09 am

There's a few grammatical errors above. Ho hum.
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Re: DIY Transistor Amp Using NVA Boards

Post by Paul Barker » Sat Mar 31, 2018 9:15 am

This is a relevant lookback that many of us here, our journey since the 1st Eggborough.

On that occasion there were quite distinct differences in sound between the amplifiers.

It wasn't many years in when some of us started looking around at each other and saying..."the standards of what everyone is doing is so raised that you'll be happy with anything here in your own home".

The NVA boards' as Steve presented them are also at that level.
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Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Wed Apr 04, 2018 12:00 pm

Paul Barker wrote:
Sat Mar 31, 2018 9:15 am
This is a relevant lookback that many of us here, our journey since the 1st Eggborough.

On that occasion there were quite distinct differences in sound between the amplifiers.

It wasn't many years in when some of us started looking around at each other and saying..."the standards of what everyone is doing is so raised that you'll be happy with anything here in your own home".

The NVA boards' as Steve presented them are also at that level.
Interesting point about the distinct differences between the amplifiers at the first Eggborough meets vs the narrowing of the distances between them at later ones.

I've been given cause to ponder a lot lately about the whole hi-fi question and am coming to a kind of realisation that is making me rethink the whole concept, throwing away 99.9% of what I thought it was about. The 0.1% that is left is the pure unadulterated Source, and looking back, that is what I think one or two people had found at those early meets.

Now could it be possible that the amplifiers that were hitting the spot at the first meets were minimalist 'pure' early 'first on the block', SET revolution designs and therefore the differences between those would have been down to individual component quality?

Does going 'simple' with a design throw a bright spotlight on the actual quality of the parts being used, right down to the type of hook up wire? I think it does. A simple SET, with AE transformers, Western Electric 211s/ Osram globe PX25s, Black Gate power supply caps....hmmm, this is going to be pretty awesome isn't it?

For me, the amps at the early meets were characterised by incredibly high quality ironware and exotic valves in very simple, no frills circuits. Speakers were using exotic full range drivers, again dead simple but very high quality and those building SETs afterwards, had superb references to work towards to improve their own efforts, so that standards were bound to rise.

BUT here's the thing. Did the narrowing of the differences happen because the rest of us upped our game or did the first division stuff become increasingly complex, more hi-fi, less music if you like, or was it a combination of those factors.

Have the absolute top class standards dropped to meet those going up resulting an equiibrium where things are "good enough" for most of us?

I say this because after a false start where I blew up the first attempt to build a DIY transistor amp with NVA boards, I've now had another go and gone for ultra simple in the power supply department. Transformer, rectifier and just single filter/reservoir on each rail. The power supply consists of only four components. I mean look at it; there's nothing in the bloody thing:

Image

And yet the result is great. I couldn't ask for a better music reproducer. It's like those SETs in the early days. There's *nothing* unsophisticated about what comes out of the speakers.
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Re: DIY Transistor Amp Using NVA Boards

Post by Nick » Wed Apr 04, 2018 2:01 pm

I mean look at it; there's nothing in the bloody thing
I count 51 parts on each of the amp boards.
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Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Wed Apr 04, 2018 2:28 pm

The power supply I mean.
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Re: DIY Transistor Amp Using NVA Boards

Post by Nick » Wed Apr 04, 2018 2:34 pm

Cressy Snr wrote:
Wed Apr 04, 2018 2:28 pm
The power supply I mean.
Fair enough.

BTW. the link on the board where the preamp and power amp parts are joined (in both rails I assume). has anyone tried a couple a diodes and caps to isolate the front end from the output stage?
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Re: DIY Transistor Amp Using NVA Boards

Post by pre65 » Wed Apr 04, 2018 2:40 pm

Do I spot an IEC mains connector ? :shock:
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Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Wed Apr 04, 2018 2:42 pm

Nick wrote:
Wed Apr 04, 2018 2:34 pm

Fair enough.

BTW. the link on the board where the preamp and power amp parts are joined (in both rails I assume). has anyone tried a couple a diodes and caps to isolate the front end from the output stage?
I thought about decoupling the stages, but blew it up before I had the chance. It looks an obvious move.
Stu might be the best person to try it out as he has a lot more experience with SS than me.

I'm bringing the amp to Owston for an outing, but I want it intact in order to be able to do that. :)
Last edited by Cressy Snr on Wed Apr 04, 2018 2:45 pm, edited 1 time in total.
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Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Wed Apr 04, 2018 2:43 pm

pre65 wrote:
Wed Apr 04, 2018 2:40 pm
Do I spot an IEC mains connector ? :shock:
Yes. It's built into a metal box, so it is easy and safe to build to Class 1 regs.
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Re: DIY Transistor Amp Using NVA Boards

Post by ed » Wed Apr 04, 2018 3:05 pm

there is stuff to think about in your progress post....

fwiw I will hope to bring a latfet 3 stage to Owston which has a much simpler vas than your circuit, in fact compared to the usual fare it is paired down considerably...

there is still stuff to chase if the interest can be sustained
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Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Thu Apr 05, 2018 7:10 pm

Latfet - sounds like something you might get in Costa Coffee. :mrgreen:

Seriously though, I'm looking forward to hearing what they can do.
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Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Thu Apr 05, 2018 7:11 pm

Made a nice little upgrade to the performance of the DIYNVA today, by subbing in a pair of 10,000uF, 80V, Supertech slit-foil electrolytics to replace the cheap 63V caps I had been using in the power supply.

https://www.hificollective.co.uk/compon ... itors.html

A bit more music is coming out of the speakers, even before the caps have fully burned in. The chief improvement is in the way low level backing instrumentation interacts harmonically. This gives a better relationship with the foreground instruments, leading to a better sense of "tune playing" as a whole.
The foundation of drums and bass underpinning the music is a little more solid and in command of the rhythm too.

Not bad value for £25 the pair, once p&p has been added in.
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Re: DIY Transistor Amp Using NVA Boards

Post by little eddy » Thu Apr 05, 2018 9:52 pm

Expensive if you have a Pass amp where they recommend a minimum of 120,000uF!
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Re: DIY Transistor Amp Using NVA Boards

Post by karatestu » Tue Apr 10, 2018 9:09 am

Cressy Snr wrote:
Wed Apr 04, 2018 2:42 pm
Nick wrote:
Wed Apr 04, 2018 2:34 pm

Fair enough.

BTW. the link on the board where the preamp and power amp parts are joined (in both rails I assume). has anyone tried a couple a diodes and caps to isolate the front end from the output stage?
I thought about decoupling the stages, but blew it up before I had the chance. It looks an obvious move.
Stu might be the best person to try it out as he has a lot more experience with SS than me.

I'm bringing the amp to Owston for an outing, but I want it intact in order to be able to do that. :)
Hello Steve (and Nick),

Les W at Avondale Audio specifies a 1N4004 and 220R in the DC power lines between output and input stages. The concept works very well with his boards and only drops a small amount of voltage. The thing is I am not sure it would be worth doing on the NVA boards as KISS applies as you have found out. As I am running separate psu's for front and back end it is rather a moot point as far as my set up goes.

My set up is still using the Avondale psu pcb's with soft recovery diodes and 12uH inductors between the 3 smoothing caps. The inductors were a nice hifi improvement with the Naim amps and the Avondale that followed. I only used to use them on the input stage psu but at the moment i have them on output and input stages. I am working on a minimalist rectifier and cap solution using MBR20200CT schottky rectifier diodes (cos i have lots of them) and 6,800uf kendeil caps (good but nothing fancy) strung together with big fat 3mm tinned copper plates. The copper plates are just an experiment and maybe no better than using the 2mm tinned copper wire but i like to try things out :D

I have not even tried bypassing the smoothing cap with a 1uf film. What did you use for the 1uf ?

Stu
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