Tube heater question/idea

[KCman]

The only reason I have the transformer is the Peavey dealer/repair shop in town clossed. I was friends with the owner/tech. He gave me a bunch of stuff from the back. He maybe didn't know about the thermal fuse.

[Enzo]

Why go through all these machinations just to cobble this particular tube set to that particular, but unsuited, PT? Just save the transformer for something else, and get a real PT for your project.


I have no problem at all with series heaters, they reduce the current considerably when compared to four in parallel. We have various amplifiers that burn up molex connectors with heater current, and this arrangement neatly solves that problem. If one heater opens, it certainly is not a challenge to figure out which one.

[g1]

You can also use the PT for the HT and run an aux. heater transformer. I think it would be cheaper than another PT, provided you have room for it.

[Chuck H]

Why go through all these machinations just to cobble this particular tube set to that particular, but unsuited, PT?

That's why I gave a thumb to post #8

Best solution IMHO. 2xel84's is a fun novelty, but IMHE you can easily find yourself under powered at a gig. Just make it four el84's with an option for just using two. Unless this is a consideration for an OT that is already at hand.?. Maybe more stuff needs to be acquired before attempting this spare parts build just to have all the parts that work together

[loudthud]

They have 12V6GTs at tubesandmore.com for $6.90 Try to find a 6V6 or EL84 for that.

[KCman]

Thanks for the 12v6 idea!

Heater current reduction when running parallel is a good point

I have been thinking about a filament transformer also

The reason for the cobbling of this stuff is purely learning. I have gigging amps and studio amps. I have nicer parts, but just wanted practice putting together "something maybe different". Without spending much money.

The chassis I'm putting it in is half of the Baldwin organ chassis. I'm not sure if I would even try to put it in a usable cabnet!

I'm limited to this PT for a small one. I have a couple giant ones. (without buying one)

Cheapest option would probably be a filament transformer, but the 12v6 idea sounds fun.

This 35 below weather always gets me dreamin up some craziness!

Thanks again!

[Helmholtz]

for the tubes in question, series heater wiring is not the best solution anyway.

The more I think about it, the less I like the idea of wiring power and signal tube heaters in series, even using suitable additional resistors.
Firstly, individual heater voltages depend on the other tubes and may vary by more than 10% as tolerances add.

But more importantly, I expect increased heater hum problems, especially if the 2 12AX7s are wired for 6.3V and connected in series, as the OP suggested.
The 12.6V heater version Juan proposed seems favorable in this respect, as it allows one of the heater pins of each 12AX7 to be grounded.

[mozz]

I've run 12ax7 on 12vac (output dual el84's in series)(old 5v, 12v, hv organ transformer) and from what i am reading they say do not use the center tap pin 9 to ground. I used 220 ohms from each leg to ground and it worked out fine. I forget the actual reasoning behind this but it made sense.