Another DIY SS Amplifier with NVA Boards

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Latteman
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Latteman »

Hey Steve- how is the Tangent Cdp behaving. I looking for a new unit - my refurbished MF is excellent but is a big box & having psu moments- currently got a ps3 doing the spinning duties - not half bad but miss the hifi-ness of the MF cdp
Analogue Source -
Diy Turntable ,- Thorens Td321 donor
Diy tonearm- Well Tempered clone,
Benz Micro Ace L
Hitachi HT-660. Ortofon Vito mc
Nva Phono 1 MC board
Digital Sources- MF M1 Clic, Diy IDE cdp, iPhone 6s.
Amplification 2x Nva A20; A30 mk2; AP10H; Khozmo passive pre
Speakers- Diy full omni bipolar 8”/6.5” & R. Allan CB4; Ls5/3
Dc blocker to Nva mini BMU

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow »

Latteman wrote: Tue Jan 28, 2020 8:25 pm Hey Steve- how is the Tangent Cdp behaving. I looking for a new unit - my refurbished MF is excellent but is a big box & having psu moments- currently got a ps3 doing the spinning duties - not half bad but miss the hifi-ness of the MF cdp
It’s doing sterling service and sounding great. Just be aware of the gapless playback issue.
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 »

Finished the cosmetics today:
9670C496-CBCE-4795-9500-376BF5635966.jpeg
9670C496-CBCE-4795-9500-376BF5635966.jpeg (115.74 KiB) Viewed 2285 times
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.
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 »

Closer pic of the finished amp:
73F55DBC-708C-488C-BA02-FF74F10B7290.jpeg
73F55DBC-708C-488C-BA02-FF74F10B7290.jpeg (65.66 KiB) Viewed 2269 times
There's fixed bias, cathode bias, grid leak bias and confirmation bias.
All my amps use the latter :mrgreen:

Alfi
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Alfi »

Looking great Steve. :clap:

I particularly like the way the top plate turned out with the meshed vents and black paint, very cool. No pun intended of course ;)

Alfi.
I am in the hi-fi trade.
Status: Manufacturer.
Company Name: Analogue innovation.

Radio_Free
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Radio_Free »

Hello Everyone,
I know this has been left off a while but I need some advice here, after going through all the posts here and the other thread started by Stu a while back.
I just bought an old AP50 (one with a chrome front plate, it’s old), and I intend to upgrade the power supply with 2 transformers (250VA each), and put everything into a bigger box.

Questions are:
1. Is it better to use one transformer for each channel like a dual mono, or one for output stage stereo and the other for the other stages? I don’t think I want to go to the extend like the A80s with 4 transformers, at least not for now.

2. I’m also thinking of implementing input chokes before the large cans, found some made by Toroidy with 10H 500mA. I’m not sure if 500mA is enough but I have difficulty finding something reasonable beyond 500mA. Also would the chokes interfere with the transformers if the sit right next to each other?

Any input or thoughts greatly appreciated.

Daniel Quinn
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Daniel Quinn »

These are you try ,you decide questions and answers.

If ma is the same as va then your fine. Again it's a question if trying and you deciding.

Ps. This is somebody's thread. I think you may get more response if you started your own.

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu »

I never compared one transformer for each channel versus separate for input and output stages. Steve has though :guiness;

Chokes- you have to watch the resistance of them. I have used very low value inductors in between psu caps. Slugs some high frequency crap although I think I prefer the sound without them.
DIY inspired by Richard "The Doc" Dunn RIP

Radio_Free
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Radio_Free »

Hello Stu,
Let me try the two combinations and will share my observations here, but probably have to be in a month’s time. Still need to wait for some parts to arrive.
For the inductors in between psu caps, I too prefer without them when I tried that with 3x4,700uF. But now I’m planning to put in just 1x10,000uF per rail so am thinking of putting a input choke before the cap. I guess I will leave that for later as I’m really not sure and I have absolutely no background on electrical and electronics education.

Hello Daniel,
Will keep your suggestion in mind. Maybe I’m not used to how things work here in this forum.

Radio_Free
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Radio_Free »

Hello Everyone,

Some quick update after playing around a bit.

I borrowed 2 old 150VA toroidal transformers from a friend and salvage some very old caps from storage and manage to hook up 2 sets of power supplies, each power supply consist of:

150VA toroidal with 2x28v secondary, 1x bridge rectifier (not those sexy fast/soft recovery ones), 2x 10,000uF 63v (some basic Nichicon stuff), each rail bypass with 10uF and 1uF film caps (old JFX series from JB caps).

So I have 2 sets of these and tried the following connections:
1. One set of power supply to one board driving all stages - like a dual mono.
2. One set of power supply driving just the output transistors of both boards, and one set driving the rest of the stages of both boards.
3. One set of power supply driving the output and secondary output transistors (the TIP31/32A) of both boards, and one set driving the rest of stages of both boards.

I must say I like the #2 setup best, cleaner and more solid baseline. I am not quite decided which is better in #1 and #3 setup, but I'm quite certain I like #2 the best.

I have tried with and without the bypass caps in all the setups and I must say it is better with the bypass caps, and I guess it helps with the not-so-great electrolytics.

As I have not reconstructed the enclosure yet, the power supplies are sitting outside the enclosures and connecting to the board via a 1-feet hook-up wire (16AWG I think). Not sure if this is too long but I was considering putting the power supplies in a separate box.

Definitely fun!!!!

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