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 » Wed Oct 23, 2019 1:09 pm

karatestu wrote:
Wed Oct 23, 2019 11:48 am
But it will no longer be an OTL Steve.
No it won’t, but to go beyond a single tube is a pain in the proverbial in terms of circuit design, and the power consumption rockets. As I’ve got older and poorer I’ve had to become more pragmatic. OK...so OTLs are undoubtedly stunning sounding pieces of kit, but the running costs in terms of the sheer amount of energy wasted on heat and the cost of replacement valves, outweigh the sonic benefits. For someone like me, on a very modest pension, OTLs are a luxury too far. They cost too much to run.

The OTL uses 100W for valve heaters and another 170W of anode dissipation in total, for output valves, input valves and rectifiers. That’s 270W idling power out of the wall to produce 1W of audio power. That’s appalling efficiency by any stretch of the imagination. A ‘normal’ push-pull, class A/B valve amp might pull 80W, which is reasonable and affordable, though not as efficient as a transistor amp, as, obviously, there are no valve heaters in those

I’ve no intention of dismantling the OTL. But for everyday use, the A60 clone is more than adequate. :)
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
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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 » Wed Oct 23, 2019 3:43 pm

At least now I’ve proved to myself that I can design and build an OTL without blowing myself up in the process! :lol:

The first attempt at the A60 clone, produced an arc-welder and a bollocking off Richard.
The second attempt produced a bloody wonderful little music maker.
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
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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 Oct 25, 2019 5:14 pm

So I’ve had a couple of days with this amp and the Fane speakers, and I can’t fault the combination, for music making ability.
If you’re interested in single driver, full range speakers, do try an NVA amp with them.

Keeping in mind that that you’d need properly designed grilles in order to get the right sound; big single FR drivers in concert with NVA amps, take Richard’s simplicity philosophy to its final conclusion, and the result is lovely. I wish he’d lived long enough to have heard this work arrive at this stage. :(
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
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Fri Oct 25, 2019 6:28 pm

Very glad for you Steve. You deserve to be happy after all the work you have done.

Richard would be complimentary i am sure. It can't get any simpler.

Would them Fane's work in an infinite baffle ? :think:
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 » Fri Oct 25, 2019 7:15 pm

karatestu wrote:
Fri Oct 25, 2019 6:28 pm
Very glad for you Steve. You deserve to be happy after all the work you have done.

Richard would be complimentary i am sure. It can't get any simpler.

Would them Fane's work in an infinite baffle ? :think:
The Fanes have a Qts of 0.64 so I can’t see infinite baffle being a problem.
Yes I’m over the moon with the results of the engineered grilles, single driver speaker and NVA amplification.It’s something I wasn’t expecting, as high damping factor, solid state amps and single driver speakers don’t usually make easy bedfellows. Sometimes, acoustic methods from the 1930s have a place in modern speaker designs, and they don’t mess with the timing information; at least not to the degree that a crossover would.
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: 1214
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 » Sat Jan 11, 2020 7:14 pm

My knackered old Sony CD player has been stripped out and is now, with the eventual addition of a new front panel going to be the home of the pair of precious NVA boards.
Below is the general idea of the internal layout:
175DAB90-5D13-4285-A16C-70D78C161BAA.jpeg
175DAB90-5D13-4285-A16C-70D78C161BAA.jpeg (101.53 KiB) Viewed 212 times
The boards will fed by a twin power supply; one for the front end and the other for the driver/output stage.
Power section off a 30-0-30V transformer/rectifier with 6800uF per rail
Front end off a 25-0-25V transformer/rectifier, with again, 6800uF per rail.
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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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Sat Jan 11, 2020 7:51 pm

Hey Steve. I don't know where you are going to split the supply rails on the amp boards but Doc had only the output transistors on the big transformer and the rest including the driver transistors on the smaller transformer.

I have tried it both ways - driver and output transistors on the big psu and the rest on the small psu and with the output transistors on their own. I preferred it the way Doc did it.

Also be careful with how you join the 0V of the two supplies. A bit of wire resistance between them works wonders i found.
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 » Sat Jan 11, 2020 8:05 pm

karatestu wrote:
Sat Jan 11, 2020 7:51 pm
Hey Steve. I don't know where you are going to split the supply rails on the amp boards but Doc had only the output transistors on the big transformer and the rest including the driver transistors on the smaller transformer.

I have tried it both ways - driver and output transistors on the big psu and the rest on the small psu and with the output transistors on their own. I preferred it the way Doc did it.

Also be careful with how you join the 0V of the two supplies. A bit of wire resistance between them works wonders i found.
Cheers Stu,
I’ll do it the Doc way. Makes sense that the power stage be isolated to prevent it talking to the preceding stages. I’d put it te other way round after looking at your thread, when you first introduced multiple power supplies. I should have read further on.
What do you mean by wire resistance?
Last edited by SteveTheShadow on Sat Jan 11, 2020 8:13 pm, edited 1 time in total.
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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Ithilstone
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Swaziland

Re: Another DIY SS Amplifier with NVA Boards

Unread post by Ithilstone » Sat Jan 11, 2020 8:09 pm

SteveTheShadow wrote:
Sat Jan 11, 2020 8:05 pm
Cheers Stu,
I’ll do it the Doc way.
What do you mean by wire resistance?
I would as well split it that way,
I think Stu ment to not connect 0 from both in the same place but rather on both sides of caps bank
Nothing to see here...

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Sat Jan 11, 2020 8:15 pm

I tried joining the two psu's 0V with a very short wire between the two different sets of capacitors and had a hum problem. When i joined them with a much longer wire it went away even though we are talking a fraction of an ohm difference. The extra resistance is the only explanation i can come up with :think:

As Les at Avondale Audio once told me - it's best to have an interface
DIY inspired by Richard "The Doc" Dunn RIP

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