Output mod

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RectifiedAmps
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Re: Output mod

Post by RectifiedAmps »

MikeC wrote: Tue Oct 19, 2021 2:46 pm
RectifiedAmps wrote: Tue Oct 19, 2021 2:30 pm
MikeC wrote: Tue Oct 19, 2021 1:47 pm

Not so easy (or possible even) to use global VVR if the amp's power stage is grid biased (which the big ones typically are).
Merlin Blencowe (the Valve Wizard) has a great VVR circuit for fixed bias amps that scales the bias in parallel to the B+. I installed it in a customer’s Bluesbreaker a while back and it worked well, although it was a bit fiddly to set up.
That sounds interesting - don't suppose you can give me a link to save me an internet hunt? Thanks.
It was in his power supplies book, but they discuss it on hoffman and have an updated schem here: https://el34world.com/Forum/index.php?topic=17083.0

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Re: Output mod

Post by MikeC »

Thanks for that, I'll have a good read.
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Re: Output mod

Post by JHorner »

Thewilltopowerrock wrote: Mon Oct 18, 2021 6:10 pm How hard is it to mod a tube amp to have multiple output levels? I.e., start with a 100w amp and mod to have a 50w output.
$130 according to these guys.
https://www.trademe.co.nz/a/marketplace ... 3311725207

No idea how well it works.

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Re: Output mod

Post by Harryclaus »

I believe it is very dependent on the amp circuit and the degree to which you are attempting to reduce it. There's the traditional "remove two power tubes out of a Twin Reverb" method, which reduces wastage by around half while maintaining a large, hefty, loud amp.

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