6V AC heater voltage

[big_teee]

Would there be any functional difference in a 6v A.C. heater supply done in these three ways?
1. 6.3 & common
2. 3.15-0-3.15
3. 3.15-3.15 & 100 ohm resistors

If they are functionally the same?
The 6.3v, & common would be easier to wire.
Not sure if the wiring on a 9 pin connector would be the same?
https://www.edcorusa.com/xpwr059
https://www.edcorusa.com/xpwr134
T

[Mick Bailey]

1. Would most likely need 100R ground reference resistors. Connecting one side to ground can result in higher hum levels.
2. Fine. Ground the CT.
3. That looks like a different way of expressing 0-6.3v and the same as 1.

All three work. Regardin 1) - I Just had a PCB amp (a Leo) where one side of the heater was grounded and it hummed badly. Floating the supply and installing resistors resulted in a near-silent amp.

[Justin Thomas]

I've never noticed a problem with hum or other heater noise in any of those three methods. I have a Champ which uses the first, and my other Fenders use the other two methods. My Bassman initially had the CT, but while rebuilding the bias supply I bumped the pilot light lug to ground and shorted my CT. So I put in the 2x100R in its place. Absolutely no difference. I thought the only thing is that there are 6V across the two ends of the heater, and that's it - the tube doesn't care how you accomplish it.

Others' experiences may vary, of course, especially with the Champ style...

Not sure about the 9-pin connector, though...

Justin

[Enzo]

WHAT 9-pin connector?

2 and 3 are the same thing, in either case the heater center tap is grounded. 2 uses an actual center tap, while 3 uses a virtual center tap.

Grounding one side is better than having it all float, but while it works on small simple amps like a Champ, which has other hum issues anyway, it will not be as successful on a larger more complex amp.

[big_teee]

Actually I was more concerned about number 1.
Two wires and one is 6.3v AC the other is common.
Like this PT?
https://www.edcorusa.com/xpwr134

T

[Enzo]

Any tube power amp will have a 6v winding. It may or may not have a center tap. Whether it does or not, there will be 6v between the 6v wires. And we wire those to the sockets. Whether one side of that is also grounded doesn't change that. What you cannot do is wire 6v and ground to the sockets AND ground a center tap. If you ground one side, then the center tap must not be used. If you ground the center tap, then you cannot ground either end of the 6v winding.


A 6v winding on the transformer is just a piece of wire that makes 6v, there is no ground on it. The only thing that makes one side ground is YOU connecting it to ground.


If you do go one side ground - I'd prefer not, but up to you - you could ground one side of each socket and run a single 6v wire to the remaining side of the sockets. or you could still wire it up with a pair of wires like every other amp in the world, and just ground one side at some convenient point.

[big_teee]

OK I get it, but this diagram says 6.3v & common.
Normally it just says 6 volt.
I was just trying to see if this was suitable.

[Enzo]

Just a drawing convention. Two wires, one on each end of the winding, and there is 6v between the ends. You can ground either end or neither if you like. Some drawers write 0v and 6v as the two ends.

It doesn;t matter here, but sometimes we use more than one winding together. Most common for us when we have dual primaries - you wire them parallel for 120v and series for 240v. Phasing is VERY important, so it matters which end of a winding is the start and the finish. Some put a big black dot on one end of the winding to indicate phase. So if I wanted to combine the two 6v windings here to make a 12v CT, I need to connect the common of the brown to the 6v of the green and use that as the CT. or i could parallel them for current capacity, in which case I'd hook the commons together and then the 6v ends together.

You may be used to seeing it drawn differently - well labelled differently - but those other conventions are also perfectly normal.

[big_teee]

Thanks for the clarification.
T