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 » Mon Jan 13, 2020 5:50 pm

Made up a base and some angle brackets to mount the heatsinks and boards:
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Output transistors have been temporarily fitted to check they are positioned right.

Below is how it all looks in the chassis:
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Amplification - NVA A20/P20
Analogue - BTE Designs Goldring GL75 turntable, Rega R200 tonearm, Audio Technica VM540ML cartridge, NVA Phono 1.
Digital - Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, Tangent CDII CD player.
Speakers - Large floor standing sealed cabs, with Fane 12-250-TC 12" full range driver.

SteveTheShadow
Posts: 1215
Joined: Thu Sep 12, 2013 5:24 pm
Location: S Yorks
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Mon Jan 13, 2020 9:42 pm

A question,
I have a choice of 3x 300W transformers for the output stage of this amp.

1x 25-0-25
1x 30-0-30
1x 35-0-35

I really want to preserve these boards and not let the smoke out of them. With that in mind, is it worth going high (35V) on the output stage? I think it may come down to whether or not I have adequate heat sinking for the 50V rails a 35V transformer would give.

I’m using a 225W, 25-0-25V on the input/driver.
Amplification - NVA A20/P20
Analogue - BTE Designs Goldring GL75 turntable, Rega R200 tonearm, Audio Technica VM540ML cartridge, NVA Phono 1.
Digital - Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, Tangent CDII CD player.
Speakers - Large floor standing sealed cabs, with Fane 12-250-TC 12" full range driver.

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karatestu
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Location: North Yorkshire
Great Britain

Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Mon Jan 13, 2020 10:56 pm

I have 35-0-35V AC transformer on my output stages. I have never had any problems although my heat sinks are mahoosive. They do get warm but never hot and my speakers are quite a bit less efficient than yours and we probably play music at similar volumes in small rooms.

It probably won't matter if you keep to the same volume as you usually do. Your speakers are efficient and with no crossover so there is not much reactance. You have the capability to supply more current but you probably won't use it (it will only be for supplying short peaks). My heat sinks only get hotter now than when i had smaller transformers on them when i want more volume.
DIY inspired by Richard "The Doc" Dunn RIP

SteveTheShadow
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Joined: Thu Sep 12, 2013 5:24 pm
Location: S Yorks
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Mon Jan 13, 2020 11:22 pm

karatestu wrote:
Mon Jan 13, 2020 10:56 pm
I have 35-0-35V AC transformer on my output stages. I have never had any problems although my heat sinks are mahoosive. They do get warm but never hot and my speakers are quite a bit less efficient than yours and we probably play music at similar volumes in small rooms.

It probably won't matter if you keep to the same volume as you usually do. Your speakers are efficient and with no crossover so there is not much reactance. You have the capability to supply more current but you probably won't use it (it will only be for supplying short peaks). My heat sinks only get hotter now than when i had smaller transformers on them when i want more volume.
Thanks Stu. Food for thought.
Amplification - NVA A20/P20
Analogue - BTE Designs Goldring GL75 turntable, Rega R200 tonearm, Audio Technica VM540ML cartridge, NVA Phono 1.
Digital - Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, Tangent CDII CD player.
Speakers - Large floor standing sealed cabs, with Fane 12-250-TC 12" full range driver.

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Latteman
Posts: 545
Joined: Tue Aug 14, 2018 7:20 pm
Location: S. Yorkshire
Great Britain

Re: Another DIY SS Amplifier with NVA Boards

Unread post by Latteman » Thu Jan 16, 2020 8:52 pm

:epopc: :epopc:
Updates please
Analogue- ARB modified Funk Firm Vector; Ortofon Mc 10 & MCa step up to Yaqin phono stage
Digital Sources- Little Dot Dac1, Musical Fidelity E600 & Apple TV
Amplification-NVA P20 & A20 (both modded)
Speakers- Diy BBCubes; Ls6
Mini BMU to dc blocker

29mile
Posts: 85
Joined: Thu Jul 12, 2012 1:20 pm

Re: Another DIY SS Amplifier with NVA Boards

Unread post by 29mile » Thu Jan 16, 2020 9:23 pm

Quick bit of advice regarding a potential project PSU to upgrade my NVA amp to 2 rails per board for input and output stages. As I am lImited by the size of my case I could use either :
a) 2 x 300va ( single secondary output ) for output stage and 2 x 150va ( single secondary ) for input ie 4 single output transformers
or b) 2 x 500va ( dual secondary outputs ) transformers for 4 rails. Plan is to use 2 x 10000uf caps for each rail for either configuration.
I understand Richard always used single secondary output transformers for A70's and above.
Technically which is theoretically better ? ( but I suspect there is no definitive answer to that )

SteveTheShadow
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Location: S Yorks
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Fri Jan 17, 2020 4:18 pm

Latteman wrote:
Thu Jan 16, 2020 8:52 pm
:epopc: :epopc:
Updates please
Nothing’s happened yet worth mentioning. There is an awful lot more drilling, cutting, filing and bleeding involved, with repurposing an existing CD player chassis, than I’d anticipated; that’s if you want to do it properly. Should be something worth reporting next week.
Amplification - NVA A20/P20
Analogue - BTE Designs Goldring GL75 turntable, Rega R200 tonearm, Audio Technica VM540ML cartridge, NVA Phono 1.
Digital - Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, Tangent CDII CD player.
Speakers - Large floor standing sealed cabs, with Fane 12-250-TC 12" full range driver.

SteveTheShadow
Posts: 1215
Joined: Thu Sep 12, 2013 5:24 pm
Location: S Yorks
Great Britain

Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Fri Jan 17, 2020 4:35 pm

29mile wrote:
Thu Jan 16, 2020 9:23 pm
Quick bit of advice regarding a potential project PSU to upgrade my NVA amp to 2 rails per board for input and output stages. As I am lImited by the size of my case I could use either :
a) 2 x 300va ( single secondary output ) for output stage and 2 x 150va ( single secondary ) for input ie 4 single output transformers
or b) 2 x 500va ( dual secondary outputs ) transformers for 4 rails. Plan is to use 2 x 10000uf caps for each rail for either configuration.
I understand Richard always used single secondary output transformers for A70's and above.
Technically which is theoretically better ? ( but I suspect there is no definitive answer to that )
Single secondary outputs need to be centre-tapped to generate a positive and negative supply off a normal bridge rectifier diode package.

This is why twin secondary transformers are are usually used. You connect the windings in series to form two ends and a centre. You then ground the centre and connect the two ends to the AC terminals of the bridge package. The pos supply to the caps then emerges from the +ve terminal of the bridge package and the neg supply from the -ve terminal.

Using single secondaries; not centre tapped, you would need four transformers in each monoblock: two to generate, the two positive supplies for input/driver and output stage, and two to generate the two negative supplies. You would also need four bridge packages: two for pos and two for neg. IMO and also Richard’s, it’s unnecessarily complex, with a lot of scope for messing up and blowing up your boards. Guess how I know.

I’d just use the two 500VA, twin secondary ones, a pair of bridge rectifiers and of course a set of 10,000u caps, and be done with it.
Amplification - NVA A20/P20
Analogue - BTE Designs Goldring GL75 turntable, Rega R200 tonearm, Audio Technica VM540ML cartridge, NVA Phono 1.
Digital - Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, Tangent CDII CD player.
Speakers - Large floor standing sealed cabs, with Fane 12-250-TC 12" full range driver.

SteveTheShadow
Posts: 1215
Joined: Thu Sep 12, 2013 5:24 pm
Location: S Yorks
Great Britain

Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Fri Jan 17, 2020 7:55 pm

OK, by popular demand here is the progress so far:
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Just the rectifiers to fit; one behind each pair of caps, plus the electrical safety earth wire needs bolting to the base of the case. This is being built to class 1 standard.



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Output transistors fitted to heat sinks. Better fixing brackets for the heatsinks were made up, creating extra work, but the heatsinks are far more solidly connected to the black aluminium plate than they were.



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Back panel.



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Four 30mm holes punched in base to draw air through the heat sink fins. Fins are sitting 6mm above the inside of the base.
There will be four corresponding holes punched into the lid of the case, backed by an aluminium mesh.
Amplification - NVA A20/P20
Analogue - BTE Designs Goldring GL75 turntable, Rega R200 tonearm, Audio Technica VM540ML cartridge, NVA Phono 1.
Digital - Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, Tangent CDII CD player.
Speakers - Large floor standing sealed cabs, with Fane 12-250-TC 12" full range driver.

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Latteman
Posts: 545
Joined: Tue Aug 14, 2018 7:20 pm
Location: S. Yorkshire
Great Britain

Re: Another DIY SS Amplifier with NVA Boards

Unread post by Latteman » Fri Jan 17, 2020 8:43 pm

Lookin good
Analogue- ARB modified Funk Firm Vector; Ortofon Mc 10 & MCa step up to Yaqin phono stage
Digital Sources- Little Dot Dac1, Musical Fidelity E600 & Apple TV
Amplification-NVA P20 & A20 (both modded)
Speakers- Diy BBCubes; Ls6
Mini BMU to dc blocker

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