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4) Touch the red probe tip to the power tube pin connected to the 1 Ohm bias measurement resistor (yellow arrow) on the
far left. This measures bias for the 6V6 in that socket position. Right down the value your DMM reads. You might
expect a value between 23mV and 25mV.
5) Repeat for the other power tube position
Okay, now I've measured my bias. Now what?
To calculate bias, there are two pieces of information you need to know: your amplifier's power tube plate voltage, and the
published value for maximum plate dissipation for the power tubes used in your amplifier. To save you some time and energy,
here are those two values:
- Approximate plate voltage for OTS Mini amplifiers
- Maximum plate dissipation for 6V6s
...and now some math. The formula for calculating bias is as follows:
�������������� ���������� ����������������������
������������������ ���������� ��������������
In most cases, amplifiers are biased between 50% and 75% dissipation. We bias the OTS to approximately 23mV-25mV
reading on a DMM.
An example is as follows:
× �������������� ���� �������������� ���������������������� × 1000 = �������� �������������� (����)
14��
× 65% × 1000 = ���������� 24����
380������
12
=
380-390VDC
=
14W
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