Another DIY SS Amplifier with NVA Boards

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NSNO2021
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by NSNO2021 »

SteveTheShadow wrote: Tue Feb 04, 2020 7:01 pm Finished the cosmetics today:
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I was going to order some black perspex, but the missus insisted on a wood finish on the front panel, so who was I to argue?
It looks pretty good with a front panel made from an off-cut of engineered pine shelving board I had lying around. The panel was given three coats of clear Briwax and buffed to a deep shine. The different rectangular areas add interest.

The body was sprayed matt black from a rattle can and the vent holes are backed with perforated aluminium, also sprayed matt black.
Woah Steve those speakers are impressive looking beasts
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SteveTheShadow (Mon May 10, 2021 7:31 pm)
Modified Airlink BPS 3110S with LDA DC filter, modified Rega Planar 8 with Benz Glider SL, LDA MCJ3 phono, NVA P90 SA MK2, FW Aleph J mono blocks, Cambridge Audio CXC, Denafrips Pontus 2 DAC, Mano Ultra2 streamer, Cisco switch, Audio Technica ATH 70 cans, Cubix MMXXI & NSNO W48.5 speaker cables

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

Wahey!
Look what I’ve been up to for the past couple of days. 😊
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I’ve been having a few anxious episodes lately, so I found myself something to get mindful with, and turned my DIY NVA power amp into an integrated. It’s roughly equivalent to the old AP50 I reckon.
At the moment, the selector switch is mounted on the rear panel until I can get hold of a piece of rod and a coupler to enable the knob to go on the front, next to the volume.
I also took the opportunity to attenuate the input with a potential divider ahead of the volume control. With this, the 2V output of the CD player and streamer drops to 800mV and with my high efficiency speakers, I can now get the volume above eight o’clock without blowing out the windows.
Richard would have had me strung up for such heresy, but the amp is now usable in a small room with 98dB/W speakers.

It works great as an integrated. There are zero noise issues.
The cover needs a respray, which I’ll do tomorrow. The booze will be coming out later.
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karatestu (Fri Dec 31, 2021 8:48 pm) • Shevans (Fri Dec 31, 2021 8:56 pm) • slinger (Fri Dec 31, 2021 9:03 pm)
There's fixed bias, cathode bias, grid leak bias and confirmation bias.
All my amps use the latter :mrgreen:

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Shevans
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Shevans »

Steve this is fantastic and brings back memories of using sensitive full range Fostex in a horn cabinet with a pair of A40’s. The telling of I got from Richard resulted in SA’s being fitted so I could control the volume better.

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

Shevans wrote: Fri Dec 31, 2021 8:55 pm Steve this is fantastic and brings back memories of using sensitive full range Fostex in a horn cabinet with a pair of A40’s. The telling of I got from Richard resulted in SA’s being fitted so I could control the volume better.
Aye, a stepped attenuator will be a better bet than a fixed PD then a volume pot,. It's something to think about for the future. End of Jan is my birthday, so I might treat myself to a SA then.
There's fixed bias, cathode bias, grid leak bias and confirmation bias.
All my amps use the latter :mrgreen:

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu »

You only need four resistors for a two channel potential divider ;)
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SteveTheShadow (Mon Jan 03, 2022 7:10 pm)
DIY inspired by Richard "The Doc" Dunn RIP

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

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Now my Phono1 board and regulator has been installed in the amplifier. The board is flown well above the amp boards on a piece of acrylic which is in turn epoxied to an aluminium strut, bolted in and running front to rear. The reg takes its pos and neg power feeds, directly from the the terminals of the pair of 6800uF caps that supply the input stage.
OK, so now there is no way of running a rod to the back so that the selector knob can go on the front, but having the selector on the back panel is something I can live with, simply for the excellent noise performance gained by having short input leads.
Obviously now, I can simply plug the record player straight into the back of the amp. I’ve fitted an earth post to take the the pickup arm ground wire. No need for a separate phono stage now, which eliminates an interconnect cable and four phono sockets. Not a hint of hum, just the usual slight hiss from the MM cart’s coils, at full gain with an ear to the speaker. No mobile phone pickup either.
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It’s now a real old school integrated. You don’t find many of them about these days. :)
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antonio66 (Sun Jan 02, 2022 11:14 pm)
There's fixed bias, cathode bias, grid leak bias and confirmation bias.
All my amps use the latter :mrgreen:

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

OK, the sound from the phono section is fantastic.
Love it. Glad I dug it out of the loft.
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savvypaul (Sun Jan 02, 2022 8:12 pm)
There's fixed bias, cathode bias, grid leak bias and confirmation bias.
All my amps use the latter :mrgreen:

antonio66
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by antonio66 »

Does this mean the valve amp has taken a back seat?

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

antonio66 wrote: Sun Jan 02, 2022 11:16 pm Does this mean the valve amp has taken a back seat?
No, not at all. It’ll get a look in. There are things the 45 amp does that the DIYNVA does not and vice versa. If I get fed up of one set of compromises, then another set will come in. It’s nice to have more than one amp, hence two differing takes on the music. Never had that before. 8-)
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antonio66 (Tue Jan 04, 2022 12:20 am)
There's fixed bias, cathode bias, grid leak bias and confirmation bias.
All my amps use the latter :mrgreen:

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

This integrated DIYNVA amp concept seems to be extremely successful. If Paul and Tomasz are resurrecting the idea of an integrated, then good on them. Offering the future NVA integrated with an upgrade of a built-in moving magnet only phono stage, at a price premium, whilst keeping MC capability and multiple regulators exclusively with the separate phonos, could be something to think about. Integrating the MM phono board into my own setup seems to have produced no problems, only benefits. In a commercial product however, it might be out of the question.
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savvypaul (Mon Jan 03, 2022 2:18 pm)
There's fixed bias, cathode bias, grid leak bias and confirmation bias.
All my amps use the latter :mrgreen:

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