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Driver heater grounding.

101.162.195.119
Posted on October 26, 2014 at 23:59:13
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
 My driver (6C6) heaters are not grounded. The heaters for the stereo amp are run in series from the 6.3V CT secondary winding on main power transformer. However, the CT is ungrounded. I currently measure 2mV (actually 1mV to 2mV) noise on the amp outputs and the noise is not irritating on my ~ 99dB eff speakers. But in the interest of better practice/ performance, should I:

1/ connect the CT to 0V signal ground;
2/ ground one side of the heater; or
3/ not be a doofus and simply leave well enough alone?

Any thoughts?

Cheers,
Ray

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

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RE: Driver heater grounding., posted on October 27, 2014 at 01:06:57
Al Noakes
 1. but also float the CT to say +20V

Al

 

RE: Driver heater grounding., posted on October 27, 2014 at 11:23:51
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Are they floating? What amp is this? Do you have a schematic?

Depending on what's going on in the amp, grounding may be a bad idea.

If they are already biased up elsewhere in the amp, and you arbitrarily ground them, you may blow out the B+ to bias+ resistor.

 

Thanks guys - I am a doofus!, posted on October 28, 2014 at 14:30:10
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
 On reading CB's post I rechecked my wiring this morning and all is well - I had in fact grounded the CT. Not sure why I thought I had left it floating, but I had not.

I will certainly consider Al's recommendation of elevating the filament ~20V above ground for my next build, which hopefully will start next month.

Apologies for wasting folks' time.

Cheers,
Ray
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

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