Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  
previous: Dan McCue I dont know why it would. Functiona... -- 2/9/2004 8:46 PM View Thread

Re: DC heathers on power amp? why not?

2/9/2004 10:49 PM
Dave B
Re: DC heathers on power amp? why not?
you can use a dc stand-off supply and put dc on all the heaters. Typically you use a series resistance from B+ to ground, lets say:  
B+ -470k-100k-ground. At the junction of the resistors filter with a 10uf cap. Your goal is something close to 75vdc at the junction of the resistors & cap.  
Now connect the center tap of the 6.3V circuit (or an artificial center tap of 2 100R resistors) to the 75vdc node you've created and viola! The benefits of dc heaters but without the extra current draw.  
The reason the power amp of a push/pull amp doesn't need or benefit from dc (besides the other reasons mentioned)is because the power amp is a humbucking circuit and any ac hum is canceled out.  
A single-ended power amp on the other hand, can benefit from dc since it's not humbucking and can have problems with ac hum.  

Dan McCue Hi Dave, I think you lost me a litt... -- 2/10/2004 2:26 AM