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I love the amp's tone in general, especially the EF86 is very sparkly and unfatiguing. THe VTB channel is pretty good at lower vol settings but at higher volumes it farts out and the crunch / munch switch makes it much worse.
To get much volume out of this channel I have to dime it, so I know I've done something wrong. My voltage readings are a little low on the power tubes, -10v It's as bad as -24vdc out of spec on the preamp plates. I believe there a leaky cap or a parasitic but no squealing is or super HF heard anywhere. If anything it's a little dark compared to 6 of my other vox-ish builds. Any suggestions ? I have pulled and checked my resistor values and tested for voltage leaks on my blocking caps in circuit without any AHA! ....moments.

Thanks for any help,


Marc

Do you have the VRM on this amp, chopstuck?

J.

Pics?

No VRM - acts a little like it though - feels current limited. I believe my lead dress is done well enough. I will measure my plate and screen current tonight. Something is up. It does sound a lot better with old US made tubes.

OK, I have a muddiness problem and tracking it down I came across a few things that were "different".

I was drawing 7.6 v+ across my 116R Kr I guess this works out to be 30 ma per tube at 350V. I changed it to a 135R and at 8.1v the draw is down to 28ma and the amp has more clean headroom and grunt. - little better-

Screens- My screen supply is at about 220v. My other amps el84 screens are set closer to the plate supply within 97-98% of the plate voltage.

Are these screens supposed to be set so low ?

I'm using the Trinity trans and boards etc..

I have looked at the layout voltages and they seem way off the mark at idle. Any ideas

OK found the problem. A way out of spec NOS CTS 1 M switch pot I got 20 years ago. It was 1.5 Megs and I think I was over driving the PI. I since went through and replaced all my salvage pots with new ones and the amp sounds much better and the controls are more predictable. Great sounding amp now.

I have to stop being such a cheapskate.

That's great News "cheapstuck"!!

NOS is not always the 'bees knees'.

_________________
Stephen
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