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Re: Building a DIY amp with NVA amplifier boards

Posted: Sat Sep 15, 2018 11:50 am
by Dr Bunsen Honeydew
Class II 0v floats.

Re: Building a DIY amp with NVA amplifier boards

Posted: Sat Sep 15, 2018 12:03 pm
by karatestu
I like the idea of it floating. One less connection to the outside world and who knows what crap is riding on the 0V mains. Only thing I have connected to mains safety earth now are the electrostatic shields between primary and secondary windings of my transformers.

That has given me another idea. Connect and disconnect the electrostatic shields whilst listening to music. See if I can actually hear any difference .

Re: Building a DIY amp with NVA amplifier boards

Posted: Thu Sep 27, 2018 4:32 pm
by karatestu
Up until now I have been powering the LTP and VAS sections from one transformer and the driver and output transistors from another (that is how Avondale split the power rail).

Today I have decided to include the drivers on the LTP and VAS psu. So the output transistors have the big transformer all to themselves. I have only done it to one of the mono blocs - the one that was still humming. I had not copied the wiring over from the silent amp yet so using the old wiring layout.

Well blow me. Hum reduced. Go figure.

Re: Building a DIY amp with NVA amplifier boards

Posted: Thu Sep 27, 2018 5:02 pm
by Lurcher300b
Go figure.
I would expect that. I assume the driver is not taking a huge amount of current, so the ripple on the driver rails will be reduced if its only powering the LTP and VAS.

Only thing that would worry me a little is the sequencing. If they are all from the same supply, they will all either have or have not power. The supply now to the VAS + driver + LTP will stay active for longer on power down as they are using less current, I don't know if any operating limits may be exceeded if the driver is powered and the output stage not. Only Richard could answer that.

Re: Building a DIY amp with NVA amplifier boards

Posted: Thu Sep 27, 2018 5:10 pm
by karatestu
Lurcher300b wrote: Thu Sep 27, 2018 5:02 pm
Go figure.
I would expect that. I assume the driver is not taking a huge amount of current, so the ripple on the driver rails will be reduced if its only powering the LTP and VAS.

Only thing that would worry me a little is the sequencing. If they are all from the same supply, they will all either have or have not power. The supply now to the VAS + driver + LTP will stay active for longer on power down as they are using less current, I don't know if any operating limits may be exceeded if the driver is powered and the output stage not. Only Richard could answer that.
Thanks for your response nick.

Sequencing on power down. Never would have thought of that. Dare not turn them off now :grin: Only kidding. I have powered the unit down but only once after checking offset etc and plugging input in.

As Richard has said earlier, its a miracle nowt has blown up yet :lol:

Re: Building a DIY amp with NVA amplifier boards

Posted: Thu Sep 27, 2018 6:15 pm
by Dr Bunsen Honeydew
Lurcher300b wrote: Thu Sep 27, 2018 5:02 pm
Go figure.
I would expect that. I assume the driver is not taking a huge amount of current, so the ripple on the driver rails will be reduced if its only powering the LTP and VAS.

Only thing that would worry me a little is the sequencing. If they are all from the same supply, they will all either have or have not power. The supply now to the VAS + driver + LTP will stay active for longer on power down as they are using less current, I don't know if any operating limits may be exceeded if the driver is powered and the output stage not. Only Richard could answer that.
No problem.

Re: Building a DIY amp with NVA amplifier boards

Posted: Thu Sep 27, 2018 7:36 pm
by karatestu
:dance:

Re: Building a DIY amp with NVA amplifier boards

Posted: Wed Jul 03, 2019 6:32 am
by karatestu
Nothing much to report here music lovers apart from coming clean about something.

I mentioned earlier in this thread about regulating the front end and driver transistors of the nva boards . Not the output transistors though as they dont want the shackles put on them and need to be free from constraint. Richard told me the boards "neither need or want regulating". I took this on board but being the curious type i had to give it a try (in secret of course).

So i used some well regarded Avondale HCR200 regulators that i had been using in my diy Avondale voyagers. A slightly higher voltage transformer is required for this to account for the regulator dropping a few volts. That is if you want to keep to the same voltages as before. You could of course just run the front end and driver transistors at a lower voltage no problem its just that clipping would occur slightly earlier. Not a problem for me as i nevercrank the amps right up.

These regulators worked really well on the Avondale amps but we are talking nva here and that is a different kettle of fish. KISS rules ok. Adding more complexity and phase changes was surely going to be bad. I dont want to comment about what they sound like just now as i need to drag this thread out a bit more and keep you all in suspense :grin:

But i think i might do a shoot out between no regs, the avondale hcr200 and some very simple lm317 / 337 regs like are in nva phono stages (for those of you that were curious enough to have a look).

TBC

Re: Building a DIY amp with NVA amplifier boards

Posted: Wed Jul 03, 2019 7:23 am
by Fretless
Well it's all double-Dutch to me Stu.
(and that's from a fluent Dutch speaker).
But keep on truckin' there. :grin: :guiness;

Re: Building a DIY amp with NVA amplifier boards

Posted: Wed Jul 03, 2019 10:59 am
by valvesRus
If and / or when the NVA assets are sorted out I could be interested in a pair of amp boards like Stu and Steve have.