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05-30-2023, 07:25 PM
Hi Guys
Yes, TUT descriptions incorporating tube pin numbers assume an octal base of the standard pin-out. You can attribute this to my own preference for octal power tubes and a dislike of EL-84s. Never paid much attention to them until I designed an EL-84 version of the STUDIO amp called the KC-25.
Note that cathode-bias is a bias METHOD, that is also known as "self bias". There is no current through Rk unless a tube is plugged in, and therefore no Vk.
NEVER operate less than the full tube complement for shared-Rk output stages.
It looks like your drawing corresponds to my drawing. If one bias pot functions then so too should the other. It may be that for the one pot to show its range the other has to be set for less than maximum current. The tubes already adjusts themselves to a specific maximum Vk (for the specific voltage environment) and once that is achieved there is no more room for adjustment. Try setting both tubes back a bit from maximum, then target the hum-balance.
Note: For hum-balancing an output stage there should be no signal entering the amp. Turn any Volume, Level or MV close to the PA input to zero.
Yes, TUT descriptions incorporating tube pin numbers assume an octal base of the standard pin-out. You can attribute this to my own preference for octal power tubes and a dislike of EL-84s. Never paid much attention to them until I designed an EL-84 version of the STUDIO amp called the KC-25.
Note that cathode-bias is a bias METHOD, that is also known as "self bias". There is no current through Rk unless a tube is plugged in, and therefore no Vk.
NEVER operate less than the full tube complement for shared-Rk output stages.
It looks like your drawing corresponds to my drawing. If one bias pot functions then so too should the other. It may be that for the one pot to show its range the other has to be set for less than maximum current. The tubes already adjusts themselves to a specific maximum Vk (for the specific voltage environment) and once that is achieved there is no more room for adjustment. Try setting both tubes back a bit from maximum, then target the hum-balance.
Note: For hum-balancing an output stage there should be no signal entering the amp. Turn any Volume, Level or MV close to the PA input to zero.
