A little tubbey

[Andy Le Blanc]

I've found the time to start trouble shooting in a more practice sense.

Headphones and korg tone works...

so far... it works pretty good, the worst detraction so far is heater hum,
I'm gonna have to go further on that one, and maybe increase the value of the clipper pot.
its ok, but I want to fiddle with it.

I'm thinking of DC for the heater, in a cathode bias you increase the bypass cap
to reduce hum, but as zero bias that's not an option.

The data represented for zero bias are at 5% harmonic distortion, I want that tone color
that tone color is the whole point.

[Jack Hester]

Thanks for posting. I've got lots of the little 7-pin tubes, and some drawings of my own, that I hope to turn into builds.

I can't remember if I posted it here, but I have a hard time keeping things in my head these days. So, if there's math involved, I put it into a little program:

12/21/13 Amp Utilities v1.0
http://www.terra-glide.net/pgms/AmpUtils.exe

There's far more available by much smarter people, here on the Internet. But, not always wanting to look for the solutions online, I try to put the most needed stuff in simple programs.

Point is, if you look over in the Tube Gain section of the program, you'll see the little 7-pin tubes that I've had use for. There are just too many tubes for me to include all. But, hopefully, I've made provisions for you to enter your own data, for the ones not included.

Jack

[martin manning]

Andy what if you elevated the heater circuit with a divider off of your B+?

[Andy Le Blanc]

I got the center taps of the 12v secondaries grounded.

Neutral ground, its back to back secondaries, it comes in at AC line, is dropped to 12v... goes into the 12v of the next PT and is stepped back up
to supply around 100v to a bridge rectifier for the PS....

The 12v 6.3-0-6.3, is treated like two 6.3 supplies, ct is grounded, on side supplies the lights and the other the tube heater
It also gives you the option for 12.6v for other tube types

it simplifies the circuit wiring, every thing is to ground, but thats the real issue
except for starting over, the easiest thing is to tack on a extra bridge rectifier and cap
lift the tube heater off the ground plane.

I'll see how it goes, I can lift the 12v ct ac off the ground plane too...
bit more work... rewire the lights and heater to float them.