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RE: Paramour And DC Heaters

There are three sources of possible hum in the Paramour circuit:

1) The 2A3 filament. In the Paramount, we use Schottky diodes and a choke filter (no capacitors), plus a filament winding that is shielded from the high voltage windings. The shield plus the leakage inductance of the filter (which is common-mode) protect from common-mode noise. The Paramour II power transformer has a similarly shielded 2.5v winding but is not capable of providing DC power.

2) The power supply. The filter is adequate to reduce hum below the residual filament hum, but if DC filament power is to be used, more capacitance and/or a choke to replace the 270 ohm resistor in the power supply would be needed.

3) The driver may pick up hum from its supply. As long as that supply is grounded, this is not usually a problem with the stock 12AT7, but the 56 and 76 have very little insulation between heater and cathode - it's rated for no more than 45v positive on the heater, and zero negative. So a DC supply here would be potentially useful. The Paramour II power transformer (Bottlehead PT-2) has enough current capacity for such a power supply, but the original Paramour does not.

Unfortunately I don't think there are any PT-2s left in inventory.


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  • RE: Paramour And DC Heaters - Paul Joppa 12:31:36 09/21/09 (0)

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