Another DIY SS Amplifier with NVA Boards

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

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The stepped attenuator has certainly improved the amp’s performance, but anything would have been an improvement on the crappy carbon pot I had in there. Just shows the importance of the quality of the volume pot and selector switch, in the scheme of things.
There is no artifice in the sound coming from the speakers; layer of hash removed and all that clichéd stuff. You only notice hash when it is suddenly absent.
I also flipped up the amp boards and put the feedback resistors back in their allotted places. The inside had become an utter rat’s nest and totally offended my aesthetic sensibilities, hence the moving of the phono board and the resistor relocation. It turned out that I was out of 18K resistors, but I did have a few 15K values.
Managing to find a pair that matched, these were installed: one in each board, so strictly speaking, the boards are no longer Richard’s intended design and I’m sure I would have got a right bollocking if he was still here and I had been stupid enough to let him find out. But unlike when I put 10K in the feedback position, 15K has not produced boring sonics, so I’m happy with the results.

Three weeks I lasted before the DIY bug hit again. :lol:
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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

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Finished everything up today.
Bleeder resistors fitted and polypropylene film bypass caps connected to pos and neg rails of both supplies.
The sound is absolutely beautiful. :dance:
It was a lot of work to fit the big stepper and selector switch, cut the front panel to suit, move the phono board and give it the best power supplies I could manage, but God, it was worth it!
DIYNVA.jpeg
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PSU diagram for those interested.
The transformer voltages are different, simply because they were what I had to hand.
SSPSU.png
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Re: Another DIY SS Amplifier with NVA Boards

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12 months since I last posted on this thread.
Have just increased the capacitance in the power supply feeding the output stage by adding 6800uF in parallel with the existing slit-foil, 10000uF. So now we have 16800uF of storage per phase on the power stages, plus 6800uF per phase on the input and driver stages.

Niiiiice 8-)
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Re: Another DIY SS Amplifier with NVA Boards

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Here are the power supplies, newly stripped, boosted and simplified:
SSPSU.png
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Top one is the power stage.
Bottom is the input/driver stage.
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Latteman (Thu May 04, 2023 2:05 pm)
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Re: Another DIY SS Amplifier with NVA Boards

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Decided to put another wood fascia on the amp. On/off switch has been moved to the back in order to clean up the looks:
IMG_0193.jpeg
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antonio66 (Sun May 07, 2023 5:25 am)
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Re: Another DIY SS Amplifier with NVA Boards

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Little bit more work on the power supply today. With this amp being roughly 50Wpc into an 8 Ohm load, I had a look at Rod Elliots site https://sound-au.com/index.html
among a few others and found that the general consensus is that 10000uF per rail is the minimum capacitance needed for a mono amp of that power. That capacitance needs to be doubled for a stereo amp, to 20000uF per rail. 3 x 6800uF in parallel works out to 20400uF per rail. So that's what I installed. The input/driver supply remains at 6800uF per rail.

There wasn't the huge leap in sound quality compared what happened with the initial increase to 16800uF per rail I did the other day, but there was a further solidifying of the the presentation. Everything is now locked and grounded in the soundstage and instruments stay separated and easy to follow no matter how loud or complex the going gets. As Richard would put it, a bit more muck has been cleaned off the window into the studio.

The PSU in situ:
SSPSU2.png
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IMG_0194 (1).jpeg
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Re: Another DIY SS Amplifier with NVA Boards

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More mods:
I've redrawn the power supplies in a better format, as done by Rod Elliot, put the 10000uF slit foil Supertech caps on the input and driver stage supply and put a symmetrical RC filter across the output of the output stage supply because a different solid-state bloke on the internet sez. I've made sure it all works but have not yet listened to the results.
SSPSU3.png
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Re: Another DIY SS Amplifier with NVA Boards

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Well, having attended the Rod Elliot school of power supply design and carried out his instructions, I’m listening to the results of my endeavours. This is the most music I've had in my room…ever 😀

It’s ridiculously good. More of the music has been let out of Richard’s boards and the results certainly give a clear understanding of where he was coming from.

From where I was with the A20/P20 starter bundle, to my own beefier, integrated version, to what I have now, I can see that there was a clear upgrade path with his electronics, which basically was down to better and better power supplies culminating in multiple setups. The same path will obviously apply to the new NVA stuff by Paul and Tomas and it honestly needs to be heard to be believed.

OK my own board mods such as doubling the feedback levels and frequency compensating the output stage, would have had Richard chasing me with an an axe, but the upgrade path I have gone along is still valid and has produced stunningly good solid state sound. Do I still need valves? Yes I do, but maybe not for power amplification. I’m going to have a look at headphone amps, active preamps and phono stages for my valve fix in future.

So going back to the NVA based amp, we now have fantastic mid range expressiveness and detail, gorgeous liquid highs, great vocals, zero screech, fast slammy bass and great dynamic range where recorded, without congestion or stress. Can’t ask for much more really. All I need now is to build some speakers with big bass drivers to let more of that bottom end out. :lol: :lol: :lol: :lol:

That’s a way off yet and my small room will probably do its best to scupper any of that stuff, but it’s something to think about.
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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

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Finished off the amp today with a major tidy up of the power supply mains wiring.
IMG_0197.jpeg
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I'm not really happy about the length of the leads from the PSU caps to the boards, but short of a complete rebuild and change of layout, there's not a great deal I can do about that. so 'feck it and listen to the music,' has to be the operative phrase.
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Latteman »

Not quite the same but a different approach to you
Mono blocks in mk1 chassis-remote 300va 30-0-30v to each board via separate rectifies and caps for input/output stages- caps are 2x63v 10000uf & 2x 6800uf each board.

Image
Image
Analogue Source -
Denon DP47f- Ortofon mc20 supreme
Ifi Zen Phono
Doug Self balanced Pre amp
Akai 4000DS mk2 R2R
Digital Sources- IfI stream, Ifi Neo idsd Dac; Tidal / Radio Paradise
Amplification Nva 30vdc mono blocks
Speakers Lii Audio F-15 in Open Baffle; Ls6
Weiduka AC8.8- for digital sources
Mini BMU for analog sources

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