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Re: Hum pot in DHT preamp ???

Posted by larry moore on November 2, 2001 at 10:03:58:
Thomas, good to see you posting. Remember having dinner with me at ny noise a couple years ago at the steak house? I just wanted to chime in and say that I too find it best to CLC or LCLC rather than current sources for DHT filament supplies.
I've been thinking about this filament bias thing too. Assuming you pick a tube that you wish to bias that has a low enough filament current, say a 71A, for example. i.e.) 5V@.25A. Then one may be able to select a diode dampener, one that will pass 250mA in this example, say two 6DM4As (or perhaps two 6ax4s like you use, if I remember correctly) in series dropping 20 volts each and experience a reduction in the dynamic impedance seen in the cathode?? This gets rid of all that power dissipation in that cathode resistor, say the 10 watts in the 160 ohm resistor as shown in the VALVE article.
Thoughts?