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Re: Old design detail on PPP tubes.......

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)


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