Mod 101 - Page 27

C) Determine the bias range for your power tubes.
For 6L6GC you want to stay in the current
range of 10 mA – 50 mA.
For EL34 you want to stay in the current range
of 10 mA – 75 mA.
6L6GC’s EL34'S
Ohm’s Law allows us to measure voltage across a
resistor and know how much current is flowing through
it.
Ohm’s Law allows us to measure voltage across a
resistor and know how much current is flowing through
it.
VR
=
I
OHM’S LAW
x
Use Ohm’s Law and the resistance
measured in step 1 to convert the
current range to a voltage range.
Use Ohm’s Law and the resistance
measured in step 1 to convert the
current range to a voltage range.
V(low)
=
10 x R
V(high)
=
50 x R
=
=
_______ mV
_______ mV
V(low)
=
10 x R
V(high)
=
75 x R
=
=
_______ mV
_______ mV
D) Change the bias pot to set a more suitable bias point.
For 6L6GC it is common to use about 35 mA
as a bias point.
For EL34 it is common to use about 45 mA as
a bias point.
V(standard)
=
35 x R =
_______ mV
V(standard)
=
45 x R =
_______ mV
Slowly turn the bias pot towards hot
until you measure a more standard
value.
Slowly turn the bias pot towards hot
until you measure a more standard
value.
D) Plug in your guitar and play. You can change the bias pot hotter or colder to see where it sounds best to
you.
Be careful not to bias the tubes too hot. When this happens you will see the entire tube filament, in the center of the
tube glowing through the outer plate structure.
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