i assembled my DIYTube ST-35 about 10 months ago; the tubes were brand new @ assembly. it has probably operated only for maybe two or three weeks straight since then(@ 24 hours a day). i have been wondering, 1)how often does one need to monitor bias settings on a tube amp, or more specifucally, a DIYTube ST-35?
also, i biased it using line voltage, which at the time averaged around 124VAC( i checked line voltage once this summer on a very hot day and it was back down around 117-119).
anyway, since biasing the st-35 for the first and only time, i got a hold of a variac, which i now use to run a "power strip" which feeds all my tube gear: 2) is it advantageous to try to run the amp at 117 or 120VAC using the variac, if i rebias at that baseline, or is it ok to run it at 124VAC, if biased at 124?
my hunch is that it must be best to try to duplicate the power transformer input spec as closely as possible if you have the luxury of doing so... or am i obsessing?
it is weird, because even on contemporary equipment, the advertised power transformer spec still varies- some say 115VAC, some say 117VAC, and yet others say 120VAC....but i swear sometimes i can hear a difference of 3 or 4 volts on my guitar amps when using a variac