I've just finished building a preamp based on a 6n1p OTL amp. It has DC heaters, 6.3 volts, bridged-rectified to 10,000uf capacitor. I put 0.5R to each leg to drop the voltage to about 6.4-6.5 volts. HV is tube-rectified, CLCRC, 4.7uf-10H choke-220-220uf. I tried to use the AC side of the heater and found out that hum level is the same as with DC. I tried doubling the capacitor to 20,000 and it's still the same. I also tried a 6.6 volt battery, same result.
Why is DC not helping in this circuit?
Why is DC not helping in this circuit?