steelwitch wrote: ↑Mon Dec 02, 2019 12:20 am...Is this an amp that would benefit from a standby switch? I felt like the voltage was low enough to avoid cathode stripping of any kind...
I'm not aware of any credible sources that raise cathode stripping as a potential issue for the tube types / application relevant to tube guitar amps. So best to regard the whole thing as being common misapprehension amongst the tube guitar amp world.
And it's difficult to come up with a HT standby that isn't something of a codge at best, a comically bad source of failure at worst, eg
https://drtube.com/schematics/marshall/1986u.gif
A 'least bad' HT standby may be beneficial in the case of silicon rectification and there being direct coupled cathode follower circuits in the amp; though the best way to mitigate the abuses that circuit puts its tube may perhaps be to use proven robust tubes, eg of non-Russian manufacture.
http://www.valvewizard.co.uk/standby.html
http://www.valvewizard.co.uk/dccf.html
https://music-electronics-forum.com/sho ... hp?t=46108
sluckey wrote: ↑Mon Dec 02, 2019 5:41 pm
They operate 6 stages in the very successful AB763 reverb models! Not recommending doing so or even saying it's a good idea, just sayin'...
Rather than the 'raw' number of stages on a HT node, I think that the issue is the number of CC gain stages that are arranged in cascade, specifically related somehow to their combined low freq extension/phase shift, total cascaded max gain and number of polarity flips.
So a TR AB763 gets away with 3 cascaded stages on its reverb channel even with old HT decoupling ecaps, probably due to the interstage attenuation; whereas the gain mode of a HRD can oscillate via the HT when the preamp node ecap goes bad (4 cascaded CC stages I think?).
But no reason not to supply the input stages of a 24 channel mixer all from the same node, as they’re intended to be used in parallel rather than cascade.