DIY HiFi Forum

Hum almost gone now

150.101.146.191

In Reply to: RE: Sorry...don't know about the Signature (Brian!) posted by Goneill on April 28, 2008 at 20:57:46

How bizarre. with volume at normal levels and my ear 2 inches from the speaker I hear nothing now. That with no input signal of course, speakers are 95 dB/W/m. The hum is simply gone.
Amp is beautifully quiet. I've been listening for about 5 hours and pushed the bias up a bit to keep it in class A for longer.

Bias is 46mA with valve-art EL34s. I looked to see if anything but the filament was glowing, There is a light blue glow visible deep inside but no red glow from the plates.
Bias current was changing quite a bit (by about 10mA) for the first hour or so. It is stable now. So the original Bias pots were fine. Something else is going on. I think I might try some different EL34, does anyone have any suggestions?

Follow Ups:

RE: Hum almost gone now - Goneill 04:10:35 05/03/08 (2)
- RE: Hum almost gone now - OzMikeH 18:27:24 05/03/08 (1)
  - RE: Hum almost gone now - mccormick 12:36:10 05/07/08 (0)

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