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Re: Hum pot in DHT preamp ???

212.185.252.196


Hi Dave!

> when do you use filament bias,

I do it wherever the power dissipation in the bias
resistor is managable.

So far I use it in my all DHT phonostage,
in the 801 linestage and 801/801 power amps.

With tubes like 26 or 71A the power in the bias
resistor would be quite small.

Josef Aigner described a filament biased 71A stage
in the latest VALVE magazine.


> do you use a current source for your filaments??? or just a
> traditional linear
> LCLC supply at an elevated voltage?

No current sources. I used them in the past, but found
passively filtered supplies to be better.
I let the filament/bias supply end with a choke.

3-phase briged with Schottky diodes ->L->C->L -> filament.

In the linestage the filament supply is about 45-50V @1.25A

Thomas

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