Finished and working - 12 valve all DHT PP 26-71a-45

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Mike H
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#46 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Mike H »

Unless its ground is connected to mains earth and thence back to case via the screen(s) of a signal lead(s). :wink:
 
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#47 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Mike H »

RhythMick wrote: Sun Aug 26, 2018 8:14 pm and also to test the effect of placing that 0v reference at different locations in the circuit.
I can't say I've noticed any difference, so have tended to put it where it is most convenient, e.g., where the component's wire leads are long enough to reach.
 
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#48 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Nick »

Mike H wrote: Mon Aug 27, 2018 1:06 pm Unless its ground is connected to mains earth and thence back to case via the screen(s) of a signal lead(s). :wink:
but in THIS CASE we are talking about the stage of an amplifier that is isolated between two transformers.
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#49 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Mike H »

AH! AH! AH! Yes! You may SAY that! You can say that if you want! Yes! Um...

:oops:
 
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#50 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by RhythMick »

:cheers: :cheers: :cheers:
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#51 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by RhythMick »

Well my own amp build has turned out to be a long hard slog, with hours stolen here and there between work. Last lap now, I thought Andrew might like this shot showing the first 2 of his 12 DC boards in the amp, on its back being wired. Since this photo the next 2 have gone in and all four have been tested.
1543265397737546.jpg
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#52 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by IslandPink »

Nice work. I like to see an amp that is so large, it's in focus at the front and out of focus at the back !
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#53 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by RhythMick »

HAHA true. You should try turning it over !

It sits on industrial heavy duty runners in my cupboard, with the power supply next to it. I think the amp is about 20Kgs and the PSU about 15kgs. Andrews DC boards are the only silicon in there.

The DC boards for the 71A are mounted inside the amp, they are only 5V @ 0.25A so the dissipation is small - nevertheless the sides are open and there's a space at the back for airflow. The DC boards for the 26 and 45 valves are mounted vertically on 2 copper sheets at the back. As it's in a cupboard I've installed 2 silent fans - my skills and ambition have even extended now to designing and implementing a circuit which uses thermistors in the amp to monitor the temperature at the top of the copper sheets, vary the fan speeds (left and right) as the temperature increases (full speed at around 60 degC) and flash a warning LED if it exceeds 70C.

It'll all end in tears, though the idea is that I stop worrying about the heat and leave it alone.
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#54 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Dave the bass »

IslandPink wrote: Mon Nov 26, 2018 9:23 pm Nice work. I like to see an amp that is so large, it's in focus at the front and out of focus at the back !
Ha! Wurd!

Didn't our-Max bring an all balanced 300B PP amp built onto a door once to Owston? (I'm sure I haven't just made that up).
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#55 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by RhythMick »

I look forward to bringing it to the next meet. I'll need some notice to book the roadies ...

I can only hope it's as good as the one I built for Geoff - that makes a pair of Lowther DX4s in bog standard cabs sound SPECTACULAR ! I'd love to hear this driving Steve's superb speakers from the last meet ... If that sounds as good as I hope it will I'll be getting him drunk and asking nicely for the recipe ...
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#56 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Ant »

It was that mental 211 pp amp that was on a door dave, put it through andrew L's ooooge coffin speakers iirc
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#57 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Paul Barker »

Congratulations Rythm Mick. I’m sure it brings you hours of enjoyment.
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#58 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by Andrew »

Well done, Mick, serious bit of kit!
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#59 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by RhythMick »

Thanks. Really looking forward to the next meet.
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#60 Re: Finished and working - 12 valve all DHT PP 26-71a-45

Post by IslandPink »

RhythMick wrote: Mon Nov 26, 2018 9:29 pm
It sits on industrial heavy duty runners in my cupboard, with the power supply next to it. I think the amp is about 20Kgs and the PSU about 15kgs.
Oh, hang on. Power supply only 15kgs ? Mine is over 20Kgs. Must try harder !
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