I have the A-100T - attempted to use KT88 and 6550 - Could NOT ADJUST BIAS.
Apparently the engineer at VAS has modified the unit (I was there) to allow ONLY the EL34 family of tubes. This means KT77 as well as 6ca7 types.
Be advised - the number - matching number that is - NEEDS to be from 28 to 34. Recently was provided an Octet of GL KT77 @ 22. I was able to set BIAS at the 9 hour use setting BUT from my experience with 'other' tubes - the final setting would or could not be achieved. I removed them - they are on their way back to the supplier.
Apparently the engineer at VAS has modified the unit (I was there) to allow ONLY the EL34 family of tubes. This means KT77 as well as 6ca7 types.
Be advised - the number - matching number that is - NEEDS to be from 28 to 34. Recently was provided an Octet of GL KT77 @ 22. I was able to set BIAS at the 9 hour use setting BUT from my experience with 'other' tubes - the final setting would or could not be achieved. I removed them - they are on their way back to the supplier.