Another DIY SS Amplifier with NVA Boards

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SteveTheShadow
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Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Tue Feb 27, 2018 2:10 pm

I asked the Doc if he minded me putting up a thread about my own adventures with NVA amp boards. He didn't mind, so here I am too.
Image

Unlike Stu who has some idea of what he's doing with solid state, I don't.

Who's gonna blow theirs up first? (here's a clue; it won't be Stu.) :lol: :lol:
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Sealed cabs with Fane 12-250-TC 12" full range drivers. Also, Winslow Burhoe/Roy Allison/Richard Dunn influenced semi-omnidirectional.

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Tue Feb 27, 2018 2:21 pm

So.....
Here is my first ever SS power supply for y'all to point, laugh, or throw up your hands in horror at.
Image
Seperate rectification and smoothing for each rail.
There'll be two of these as I'm going with monoblocks.
Dead simple PSU, because, as I've found with my valve projects, simple is best (at my level it is anyway)
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Sealed cabs with Fane 12-250-TC 12" full range drivers. Also, Winslow Burhoe/Roy Allison/Richard Dunn influenced semi-omnidirectional.

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Tue Feb 27, 2018 2:22 pm

Oh, come on now Steve it's not a race to see who can blow them up first :auto-ambulance: You cant learn how to fix it until you have blown it up :grin:

Plenty of support here from Doc, DSJR, me and others probably. :romance-grouphug:

Stu
Naim, Linn & Harbeth fanboy

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Tue Feb 27, 2018 2:26 pm

I've got to get all the bits in before I can do anything, so I'll be looking at what you do anyway. That's my learning intention.

With valve amps I'm scared of frying myself with high voltage . It's a bit of a culture change to be scared of making an arc welder. :lol:
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Sealed cabs with Fane 12-250-TC 12" full range drivers. Also, Winslow Burhoe/Roy Allison/Richard Dunn influenced semi-omnidirectional.

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Tue Feb 27, 2018 2:42 pm

Any reason why you are not using centre tapped transformers or one with two secondary windings which can be joined to make a centre tap ?

I have usually used a centre tap arrangement and I believe the Doc does too going from the pics of the innards I have seen.

I like your idea of obtaining plus and minus from separate rectifiers. I have seen it done before but using centre tapped secondary windings and only two rectifier diodes in each rail.

stu
Naim, Linn & Harbeth fanboy

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Tue Feb 27, 2018 3:01 pm

karatestu wrote:
Tue Feb 27, 2018 2:42 pm
Any reason why you are not using centre tapped transformers or one with two secondary windings which can be joined to make a centre tap ?

I have usually used a centre tap arrangement and I believe the Doc does too going from the pics of the innards I have seen.

I like your idea of obtaining plus and minus from separate rectifiers. I have seen it done before but using centre tapped secondary windings and only two rectifier diodes in each rail.

stu
Only reason is I want full-wave rectification for each polarity and taking two 0-30V windings and rectifying them seperately to provide the pos and neg rails is the most economical method.
I used to swear by centre tapped rectifiers with valve amps but have used bridges for years now. Of course valve amps only have a positive supply, so I simply did a negative supply the same way and put one back-to-back with the other.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Sealed cabs with Fane 12-250-TC 12" full range drivers. Also, Winslow Burhoe/Roy Allison/Richard Dunn influenced semi-omnidirectional.

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Re: Another DIY SS Amplifier with NVA Boards

Unread post by Alfi » Tue Feb 27, 2018 3:31 pm

This looks like fun Steve.

I'll be watching closely and keen to learn about how it will finally perform.

Alfi.
Heavily modified LP12, Sole VIII sub-chassis, "In Sole" advanced polymer suspension, Ai bearing, PU7, DV20X2, Norton Airpower clone. Technics SL110A, AT 1005, Denon DL301A. NVA Phono 2 MC (2 power supplies), NVA P50 SA, NVA A40 Mk1 power amps, custom birch ply Allison 6/NVA Cube 1 clones, NVA TIS mk2 , SSC, LS6.

_D_S_J_R_
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by _D_S_J_R_ » Tue Feb 27, 2018 4:06 pm

I appreciate I'm no engineer so am open to all manner of crap from those that 'know...' in what follows...

Why only one transformer? The types NVA use aren't silly money each and space apart, it's not going to cost loads to have one transformer a side. I get the feeling that two slightly smaller ones *may* offer the same output current as one slightly bigger one supplying both channels...

Supply caps - Hmm. I started mine with 4700uF caps and doubled up (the larger amp has two 10,000uF per channel, the smaller two 4,700uF a side - adding 1000uF 'bypass' made no difference at all). Apart from the time taken to stop after switching off the power I'm darned if I can hear any real meaningful difference and of course, I have pukka smaller sized NVA amps to compare them to. I suppose it also depends on the physical capacity of the transformers you're using, as I've not used greater than 120VA at 30V secondary's into pretty easy speaker loads. I don't remember getting a definitive answer from The Doc on this, but watch that using huge supply capacitance and over 'a bank of caps' isn't willy-waving rather than actually getting more music out. maybe allowing enough space and construction symmetry you may be able to add a pair at a time to see if there's any sonic difference into 'normal' speakers. I do appreciate that Krells of old were designed to power large amounts of Watts into 2 ohm loads from Apogee and Maggie panels, but normal speakers, especially the types you lot make and use, don't need all this surely? - and 'sonic subtlety' is the key.

P.S. to me - Maybe I should try to beg or borrow some A80's to hear what the larger amps are all about - bigger supplies for the outputs at higher voltage for the extra power and I think, twin supplies per channel too. Maybe of the Doc trades some in (against a Statement amp?) he might let me borrow them for a short while?

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SteveTheShadow
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by SteveTheShadow » Tue Feb 27, 2018 5:33 pm

_D_S_J_R_ wrote:
Tue Feb 27, 2018 4:06 pm
I appreciate I'm no engineer so am open to all manner of crap from those that 'know...' in what follows...

Why only one transformer? The types NVA use aren't silly money each and space apart, it's not going to cost loads to have one transformer a side. I get the feeling that two slightly smaller ones *may* offer the same output current as one slightly bigger one supplying both channels...
I am not proposing to use one transformer to supply both channels.
The intention is to do monoblocks, therefore the power supply I have drawn is for one channel and it says so in the bottom right hand corner. So of course there will be one of those PSUs per mono amp.

Your 1000uF bypass would make no difference if it is what I think it is. To bypass electrolytics, you need a small value film cap so the resulting high pass filter shorts any high frequency noise to ground. It's arguable whether these are required with modern low ESR electroytics, some people use them, others don't.
Last edited by SteveTheShadow on Tue Feb 27, 2018 5:42 pm, edited 2 times in total.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Sealed cabs with Fane 12-250-TC 12" full range drivers. Also, Winslow Burhoe/Roy Allison/Richard Dunn influenced semi-omnidirectional.

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karatestu
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Re: Another DIY SS Amplifier with NVA Boards

Unread post by karatestu » Tue Feb 27, 2018 5:35 pm

Hi Steve,

Below is the psu i use now and will be using with the nva boards. This is one channel only....hope it makes sense

Image

I was told it is better because two diodes are removed from the 0V connection between the smoothing caps and transformer. It may be all bollocks though. Don't let this sway you from using what you drew earlier.

Stu
Naim, Linn & Harbeth fanboy

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