2A3 "Pink SET" Amp Rebuild.

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#31 Re: 2A3 "Pink SET" Amp Rebuild.

Post by jack »

ed wrote: Sun Feb 11, 2018 11:35 am btw: how did you manage to attach a pic that was 1.1 mB?
He didn't - he linked to it on imgur.com
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#32 Re: 2A3 "Pink SET" Amp Rebuild.

Post by ed »

ahha! sneaky!

Image

I get it...but my previous method allows enlargement within the bounds of the uploaded size...by linking to a remote jpg you are restricted to the size allocated to fit in thescreen frame....

swings and roundabouts by the look of it
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#33 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Cressy Snr »

Aye Ed, that's a proper 2A3. :)
That finish is beyond anything I could achieve. Is that maroon paint job, the one you got done in Alford?

Both channels up and running:
Image
Hope the bloody thing still sounds right decent.
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#34 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Cressy Snr »

Greeted with buzz.
More noise than with the AC filaments.
Job is abandoned for now I'm afraid.
I've better things to do with my time than spend weeks messing about chasing noise, not when my NVA A20 does a perfectly good job for my needs. That's the clincher really, and the sound of the pink SET is now thin, hyper detailed and and shouty; rather than the lush, real and musical sound it had before I fucked it up. The pattern continues, build something special and balls it up through not being able to leave it alone. It has to stop.

Someone with more knowledge/patience than me needs to chase down the problem, which is pretty fundamental as it is on both channels and very spiky in nature. Personally I can't be arsed. It won't stand another rebuild and neither will I, so for the present and maybe going forward, the future does not include valves.

Speakers are my primary interest and that's where I'm going with this hobby.
Last edited by Cressy Snr on Sun Feb 11, 2018 3:02 pm, edited 3 times in total.
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#35 Re: 2A3 "Pink SET" Amp Rebuild.

Post by ed »

Cressy Snr wrote: Sun Feb 11, 2018 2:06 pm Aye Ed, that's a proper 2A3. :)
That finish is beyond anything I could achieve. Is that maroon paint job, the one you got done in Alford?
You're far too modest Steve.....the pink one sets the bar, no dispute!
however the example I showed was a failure..it was done in Alford, but Dave the friend who sprayed it got the mix wrong. He was aiming for the one he'd done for me previously, which I thought was a better colour...

Image
The first one I showed is still working in the studio set-up but in truth I don't think it was as good as yours at the last incarnation at Steves. Having said that, the F6 is still on top for me.

Next time out there may be 2 more SS amps to consider...I'm working on the single ended choke loaded source follower and also a pp lateral fet using 2sk1058/2sj106...It's all your fault for displaying what 15 watts out of the wall can produce.
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#36 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Cressy Snr »

Well Ed, I think you are right on the button with the SS stuff.
Transistors don't have to sound crap, as the products RD, Nick and Nelson Pass produce, show perfectly.
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#37 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Cressy Snr »

Cressy Snr wrote: Sun Feb 11, 2018 2:31 pm The pattern continues, build something special and balls it up through not being able to leave it alone. It has to stop.
How does one break this destructive pattern?
I can't think of any way other than a total thermionic detox.
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#38 Re: 2A3 "Pink SET" Amp Rebuild.

Post by pre65 »

It may prove to be even better than before once the problem is sorted.

I have use those filament modules on 300b without issue in the past.

Give it a few days then see if you can see what the fault might be.
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#39 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Cressy Snr »

I think I might have messed up the grounding. The noise sounds suspiciously like switching spikes being injected into the signal path.
It's not helped by having the power supply running down the centre. I thought I was being clever, with the pseudo dual mono construction, but this PSU has been a complete bastard from day one.

It might involve a complete strip down, build it all up on a piece of wood without all that pseudo dual mono nonsense, and ONLY build a proper chassis when I'm sure it'll work properly. I know the panel have been going on about the need to do this for ever and I think I have had enough unsatisfactory builds to realise that it's about time I listened.

I also badly need to read up on grounding. I have to admit I don't understand the concept sufficiently well.
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#40 Re: 2A3 "Pink SET" Amp Rebuild.

Post by pre65 »

Steve, you sound a bit more positive about the amp now.

I'm sure you will get it right before long. :)
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#41 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Nick »

I also badly need to read up on grounding. I have to admit I don't understand the concept sufficiently well.
Think about the current flow and consider capacitors short circuits.
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#42 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Paul Barker »

I thought somewhere in the conceptual stage of this build one element decided on was simplicity. I’d take a step back. I like the Steve Bench hum cancellation which doesnt sound simple but it is much simpler than a quality dc supply. Its passive, in that it doesnt form the heater supply it injects the 100hz elsewhere out of phase to cancel. The ac heater supply is simplicity exemplafied.

I copied it into a google doc of my own in case his stuff ever vanishes off the web. https://docs.google.com/document/d/18mp ... DHXFX4snIM
Last edited by Paul Barker on Sun Feb 11, 2018 5:59 pm, edited 2 times in total.
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#43 Re: 2A3 "Pink SET" Amp Rebuild.

Post by IslandPink »

Cressy Snr wrote: Sun Feb 11, 2018 5:16 pm I think I might have messed up the grounding. The noise sounds suspiciously like switching spikes being injected into the signal path.
It's not helped by having the power supply running down the centre.
Bear in mind most of the WAD amps were like this.
I'll bet there's something you've missed and you'll fix it in a few days.
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#44 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Paul Barker »

the pink set as i heard it was way too good to give up on.
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#45 Re: 2A3 "Pink SET" Amp Rebuild.

Post by Cressy Snr »

IslandPink wrote: Sun Feb 11, 2018 5:58 pm
Cressy Snr wrote: Sun Feb 11, 2018 5:16 pm I think I might have messed up the grounding. The noise sounds suspiciously like switching spikes being injected into the signal path.
It's not helped by having the power supply running down the centre.
Bear in mind most of the WAD amps were like this.
I'll bet there's something you've missed and you'll fix it in a few days.
I think I have a fundamental problem because of the twin cap banks. Nothing wrong with twin cap banks per se, but reading up, I think I have made a silly mistake that virtually guarantees problems. Using twin busbars, one running along each bank makes it virtually impossible to ground without introducing noise all over the place.

The first thing to try is to remove one cap bank from the equation and run off a single bank, with an E shape grounding setup; the arms of which which will pick up the bottoms of the cathode resistors and LED from the other channel.
Last edited by Cressy Snr on Sun Feb 11, 2018 7:21 pm, edited 1 time in total.
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