DIY Transistor Amp Using NVA Boards

For the three and more legged things
Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:10 pm

It started with an email from RD offering me a chance for a small fee, to use a pair of his amplifier boards and associated output devices, and build my own amp with "NVA Inside" (copyright Intel) I snatched his hand off.
A couple of days later, a package arrived:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:12 pm

I found a power supply in MJ 4th edition:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:15 pm

Started to order some bits, caps, wire, heatsink mounting epoxy, a few 25A bridge rectifiers and this nice case off eBay:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:18 pm

A few days later the bits arrived. I ran the layout below past Richard, who gave it the go-ahead:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:21 pm

Got the hardware mounted and the output devices glued down, with a two part, heat conductive epoxy adhesive made for the purpose:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:23 pm

Power supply wired in and giving two polar opposite voltages:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:26 pm

It all fired up correctly, nothing exploded. Here it is on soak test a couple of weeks ago:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:29 pm

Amp on first introduction to the rest of my system:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:31 pm

Finished job, complete with LED indicator:
Image
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 12:42 pm

The amp sounds excellent and is, after a fortnight of use, burned in beautifully and providing some mighty fine music.
Richard did me a great deal on some old, original NVA, LS5 speaker cable, which completed the picture perfectly.

I've fitted a pair of 1uF film caps across the final power supply electrolytics, since the picture above was taken.
Both Richard and Nick advised me to do this. The effect on the sound in the treble region was useful, adding that last degree of refinement and air.

Thanks to Richard for allowing me privileged access to his amp boards, for the advice on how not to blow it up and to both Richard and Nick for keeping me on the straight and narrow during the build.

It keeps me up, listening, late into the night. Awesome :D :D

Building this is the reason why I've been asking about easily understood introductions to solid state audio engineering.
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

little eddy
Old Hand
Posts: 573
Joined: Sun Nov 09, 2008 2:06 pm
Location: Manchester

Re: DIY Transistor Amp Using NVA Boards

Post by little eddy » Sat Mar 24, 2018 1:16 pm

Nice build as ever.

Looks so simple - I must be doing something wrong.
Thorens TD-125 & 'Snail' phono/pre, NAS/SBT, CS4398 DAC, Rocky KT66 amp, still messing with OBs.

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 2:26 pm

I kept it dead simple, as I'm basically thick when it cmes to solid state.
Also, the Doc advised that less is more with his boards, so I did as he said.
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

User avatar
Dr Bunsen Honeydew
Old Hand
Posts: 1358
Joined: Mon Sep 21, 2009 10:50 am
Location: Muppet Labs

Re: DIY Transistor Amp Using NVA Boards

Post by Dr Bunsen Honeydew » Sat Mar 24, 2018 3:09 pm

I am not starting to supply for DIY or kits, it is too much hassle and potential magic smoke, BUT Stu and Steve were different. Stu is hilarious (chainsaw hi-fi) plus a good solid state understanding and he entertains us at HFS with his continuous hi-fi adventures. Steve is just a nice bloke who appreciates help and information and has no ego or need to make himself into a guru, in other words genuine!! I watch his speaker fun and tried to help, and he bought a nva starter kit which he appreciated. Not much dosh so I decided to help push his music along for him.

So basically like in all things I need motivation, It is not done for money, it is done because it entertains me, or I see a genuine need. Dunn haters need not apply, one already did at HFS and got short shrift, so there is a maybe to others.

Cressy Snr
Social Sevices have been notified
Posts: 8043
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

Re: DIY Transistor Amp Using NVA Boards

Post by Cressy Snr » Sat Mar 24, 2018 3:15 pm

Cheers Richard,
It turns out that I've now acquired three awesome amps, for not a lot of money. So maybe a bit of tri-amping of a set of giant omnis would be in order. :lol: :lol: :lol:
Or maybe not. The missus would kill me for sure. :mrgreen:
Ha - ha said the clown. Has the king lost his crown, is the night being tight on romance?

User avatar
Dr Bunsen Honeydew
Old Hand
Posts: 1358
Joined: Mon Sep 21, 2009 10:50 am
Location: Muppet Labs

Re: DIY Transistor Amp Using NVA Boards

Post by Dr Bunsen Honeydew » Sat Mar 24, 2018 3:32 pm

I wouldn't advice mixing the valve with the solid state. NVA has different input sensitivity to account for the loss of gain from a passive pre-amp.

It would be nice to hear from you the benefits or not, strong points v weak points of the valve v solid state amps as I have very little experience of valve work and what I have goes back to the 60's.

Not asking for a winner.

Post Reply