Convert fixed to cathode-bias

·$110 for 2 power-tube amp
·$130 for 4 power-tube amp

Convert fixed bias to fixed-adjustable-bias


Convert cathode-bias to fixed-adjustable-bias

·$120-180 depending on whether power transformer is equipped with a tap for this or if we need to wire a new circuit to generate a negative bias supply voltage.

Cathode/fixed bias switch

·$100 if amp is fixed-bias
·$100-140 if amp is cathode-bias

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