Another DIY SS Amplifier with NVA Boards

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Sun Mar 25, 2018 10:09 pm

Yes
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Tue Mar 27, 2018 1:25 pm

New 300VA, 30V, twin secondary, potted toroidal transformer arrived this morning. Chassis has been made ready for the transplant.
Image
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Tue Mar 27, 2018 2:44 pm

:epopc: :epopc: :epopc: Looks juicy Steve :epopc: :epopc: :epopc:
Naim, Linn & Harbeth fanboy

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Tue Mar 27, 2018 5:48 pm

Job done, working nicely on the right voltage now.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Sun Apr 01, 2018 9:28 pm

OK it's Easter weekend, and they do say that confession is good for the soul, so, I've a bit of a confession to make.
Last week I buggered about one time too many, by replacing the mains transformer and let the smoke out.

The following is a tale of how not to approach the soldering in of a set of output devices, and how you learn from mistakes.

I strongly suspect that my hairy-arsed, red hot poker, valve amp soldering technique, does not....er..... translate very well to the fitting of solid state devices into PCBs. The way I connected the output devices to the boards was, shall we say, a little crude, involving 1.6mm tinned wire "prongs" that were, with hindsight, way too thick and completely unsuitable.

Although they fitted into the holes on the PCB, they required too much heat to solder in. Now there is a small red capacitor nearby and when I did the initial fitting in of the prongs I was a bit cringy about the possibility of damaging that cap with ham-fistery, but it doesn't stop there. The prongs were meant to emerge next to their respective output device pins, which were sticking up vertically from said devices. This bit was successful (aren't I clever :roll: )

Soldering the device pins to the prongs went OK....ish, but again I was concerned that I was leaving the iron on a bit too long for comfort; particularly as the "prongs" crossed the device pins really near to the thick bits, where they enter the transistor bodies....again not good practice, Ive learned, because you are heating the pin perilously near to where it enters the device and thus stand a lot more chance of damaging the junctions inside, through overheating. TBH, when I step back and really think about it; it's a wonder it worked at all, in the first iteration, let alone sound so fantastic. :oops:

Anyway, after acquiring another pair of boards and a bollocking, a promise was made to myself NOT to repeat those mistakes and I set about rebuilding the power supply and rectification, keeping everything simple, straightforward and making sure I handled the output devices with respect.

The power supply was stripped back to the simplest possible configuration (bottom right on the set of diagrams below):
Image


The KISS philosophy the Doc ordered, resulted in this:
Image

Once the power supply had been tested, I emailed Richard, who approved it and gave it the go-ahead.
This morning then, I put on a bit of Mozart, carefully soldered in the output devices from underneath the boards as Stu had done with his "chainsaw" NVA amp, fitted some rubber feet to the undersides of the boards and glued the output devices down.
Image

A bus bar grounding system was incorporated, everything checked, then checked again, meters put on each rail, speakers attached and the thing fired up and left soaking for three hours. DC offset was checked from time to time during those three hours and all remained stable and silent. A new LED indicator with current limiting resistor was fitted, front panel and top plate attached and the amp reintroduced to the LS5s and my speakers.

It is now playing in the system, and sounding lovely. "All was well" as they said in Harry Potter.

Valuable lessons learned.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Mon Apr 02, 2018 9:28 am

Sorry to read about your little tale Steve.

Did the magic smoke appear when you changed transformer and increased the voltage ?

How easy was it to remove the glued down output transistors ?

Oh, and how big was the bollocking you acquired ?
Naim, Linn & Harbeth fanboy

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Mon Apr 02, 2018 10:26 am

karatestu wrote:
Mon Apr 02, 2018 9:28 am
Sorry to read about your little tale Steve.

Did the magic smoke appear when you changed transformer and increased the voltage ?
It all worked fine for about 5 minutes after the transformer transplant, then poof! on the left channel.
As I hinted at in the previous long post, my theory is that I'd weakened one of the transistors in the LH output pair.
due to ham-fisted soldering. May also have compromised the little red cap between two of the pins.
I got away with it with the 25V transformer, but something, either the cap or the device, let go when the higher voltage was applied.
How easy was it to remove the glued down output transistors ?
The output transistors were reasonably easy to get out, because of the bolt up case. I had remove one side of the case, snip off the device pins, remove the boards, then shock the devices off the base with a hammer and chisel. This sounds extreme but it wasn't really - a single sharp tap did the trick.
Oh, and how big was the bollocking you acquired ?
A bit of artistic licence there. It wasn't really a Sgt Major type of bollocking, more of a constructive ticking off, with advice, from the CO.
Basically it was emphasised that solid state is far less forgiving of ham-fisted handling than valves and I took from that, that it was assembly technique that needed the attention rather than any lack of knowledge on my part.

The new amp is working fine now, and I've learned something. The sound quality of the amp with this greatly simplified infrastructure is interesting and I'll talk about that later. Let's just say for the moment, that I understand far better, the Doc's philosophy about the inverse relationship between complexity and access to the music.

It's a difficult concept to get your head around unless you build something and actively use those ideas.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Mon Apr 02, 2018 12:32 pm

Thanks Steve. I like the bit about inverse relationship between complexity and access to the music. My interest and experiments are increasingly heading in that direction. I look forward to your observations since you have simplified the psu.

It has been difficult to forget all the things that i thought i had learnt. We used to take the piss out of the Naim agricultural regulator but it was simple - lifted straight from the LM317 data sheet. Spent years playing with psu's and "improving" the regulators. This seemed to bring benefits with Naim and Avondale gear but not necessarily musical benefit as i wasn't tuned in to that back then. NVA circuits are obviously different and need to be treated as such. Plus i now know where i was going wrong :dance: adding more and more complexity.
Naim, Linn & Harbeth fanboy

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Mon Apr 02, 2018 12:51 pm

karatestu wrote:
Mon Apr 02, 2018 12:32 pm
Thanks Steve. I like the bit about inverse relationship between complexity and access to the music. My interest and experiments are increasingly heading in that direction. I look forward to your observations since you have simplified the psu.

It has been difficult to forget all the things that i thought i had learnt. We used to take the piss out of the Naim agricultural regulator but it was simple - lifted straight from the LM317 data sheet. Spent years playing with psu's and "improving" the regulators. This seemed to bring benefits with Naim and Avondale gear but not necessarily musical benefit as i wasn't tuned in to that back then. NVA circuits are obviously different and need to be treated as such. Plus i now know where i was going wrong :dance: adding more and more complexity.
+1 Absolutely everyhing you've said there Stu particularly re the bit about adding more complexity not necessarily being a good idea.

Here is a pic of the innards of amp number 2.
Image
As can be seen, the internal build quality is far better than amp number one.
Everything, from the mounting of the boards/output devices, to the bus bar earth routing and the mains side switching has been given careful attention, thought through properly and appropriately insulated.
On the aesthetic side, the inside looks good and even the colour of the speaker feeds has been changed from red to black, so that they can no longer be seen through the top cover slits.
Bypass caps have yet to be experimented with, but I'm leaving well alone at the moment.
This is now a build I can take a bit of pride in and it's up to the standards I normally produce.
Last edited by SteveTheShadow on Mon Apr 02, 2018 12:55 pm, edited 1 time in total.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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Dr Bunsen Honeydew
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Dr Bunsen Honeydew » Mon Apr 02, 2018 12:52 pm

You two are having more success promoting my ideas than me, I spent over 30 years pissing into the wind, keep it up you are both getting there. You are nearly ready to build your own lightsabers :mrgreen: :geek:

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