In Reply to: Old design detail on PPP tubes....... posted by Jimmy on February 20, 2005 at 08:35:54:
They are there to supress parasitic oscillations in the VHF/UHF range. The tubes have plenty of gain there, and the connecting wires have a resonant frequency in that range... so a parallel audio circuit becomes a push-pull UHF oscillator! Sometime a low value resistor is enough, sometimes it's a combination, often a choke wound on a 47 Ohm resistor.Not all amps use them... not all amps are stable, either...
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- Re: Old design detail on PPP tubes....... - Tom Bavis 02/20/0513:00:15 02/20/05 (0)