Zener Bias

alexistheo · 24th March 2006, 12:52 AM

In the most recent audioXpress (apr 06), there is a push-oull 25L6 stereo amp. In it, Bob McIntyre uses two 7.5V zeners to bias each output tube. I was under the impression that zeners were noisy as cathode bias elements. Adding bypass caps to shunt any noise would seem to defeat the whole purpose of using them... so i'm curious: has anyone here tried zener bias of an output stage successfully?

Geek · 24th March 2006, 02:43 AM

I haven't tried zener biasing audio tubes, but it works great in RF PA's

The noise a zener gives off will be moot on an output tube. The driver or other low-level pre's maybe, but not on the output unless you have insanely sensitive speakers perhaps.

24th March 2006, 12:52 AM	#1
alexistheo diyAudio Member Join Date: Jun 2004 Location: New York City	Zener Bias In the most recent audioXpress (apr 06), there is a push-oull 25L6 stereo amp. In it, Bob McIntyre uses two 7.5V zeners to bias each output tube. I was under the impression that zeners were noisy as cathode bias elements. Adding bypass caps to shunt any noise would seem to defeat the whole purpose of using them... so i'm curious: has anyone here tried zener bias of an output stage successfully?

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24th March 2006, 02:43 AM	#2
Geek diyAudio Member Join Date: Sep 2004	I haven't tried zener biasing audio tubes, but it works great in RF PA's The noise a zener gives off will be moot on an output tube. The driver or other low-level pre's maybe, but not on the output unless you have insanely sensitive speakers perhaps.

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