Heater circuit ground reference

[ducati guy]

I recently picked up a pair of Magnequest PGP 8.1 power transformers to use in a 45 based amp. Wasn't aware that the 6.3 V supply for the driver tube is not center tapped. Do I need to reference the voltage to ground through a pair of resistors or can it float?

Conrad

[Grainger49]

I can't really answer about a power amp, but I built a preamp quite a few years back and it hummed like a mother till I grounded one leg of the heater supply.  

[Len]

I recently picked up a pair of Magnequest PGP 8.1 power transformers to use in a 45 based amp. Wasn't aware that the 6.3 V supply for the driver tube is not center tapped. Do I need to reference the voltage to ground through a pair of resistors or can it float?

Conrad

I think it's internally grounded. I didn't ground the heater supply in my Paraglows, IIRC, and they sound fine.

[Grainger49]

OUCH!  If they are internally grounded don't ground the transformer or the DC output.  Check for a ground to the frame of your transformer from each lead of your transformer.  If it reads open then it is safe to ground one leg of the DC supply.  I use the negative, I don't know if it makes a difference.

[Doc B.]

The 6.3V winding is not grounded to anything inside a PGP 8.1 transformer. It's hard to give a definitive answer without knowing the actual circuit, but assuming that the driver tube does not have its cathode sitting at a high potential relative to ground (i.e., its grid is not direct coupled to a high voltage input stage that sits before it in the circuit) you would most likely want to ground the 6.3V secondary.

[Len]

Darn! Glad you guys stepped in. My memory seems to be going.

And my memory seems to be going, too.