An interesting bias meter, for up to 100ma.
http://cgi.ebay.com/100mA-mA-meter-for- ... 93QQrdZ1QQ
So, how to hook it up?
Forget about individual tube biasing. Use
one meter per PP pair and connect the 8s
and 1s of a pair of EL34s, as in the original
dynaco schematic, but leave out the
resistor. Put the meter 'between the 8s'.
(We are measuring combined cathode
current here, correct?) Hook up the other
PP pair identically. Shoot for a hair less
than 100ma on the meter with a bias
pot per pair. Leave the meter in circuit
constantly or switch it in and out with a
SPDT switch? Won't the switch make
hideous popping noises, if moved when
the amp is running?
Or, stay with individual tube bias. Use 1
meter per PP pair, and put the meter
'between 1 and 8' of each tube. With a
rotary switch shunt the current thru the
meter or have it bypass the meter,
altogether. Hook up the other pair
identically. Shoot for 50ma on each
tube with the bias pots.
Or, just use 1 meter per amp and a rotary
switch?
Where am I going wrong?