Dual Bias

[trem]

Is there an existing schematic I can look at.?
I would like a dual bias, to be used with bias-vary Trem. But I am not at all sure how to build it.
I assume I would take it from the high voltage secondary of the PT.

The attachments show the Tremolo and phase inverter I stole from an Ampeg. The hand drawn schem shows my rectifier circuit.
Thank You

[kleuck]

What do you mean by "Dual bias" ?

[trem]

These tubes are available NOS, but who knows what the Matching/Current Draw will be.
So I would like to have a separate bias pot for each tube, that will work with the bias-vary trem in the schematic.
Thank You

[kleuck]

Just use a separate cathode resistor and cap for each tube (i do the same) Use a resistor of double the original value, no need to change the caps value.

[kleuck]

Example : Just use a separate cathode resistor and cap for each tube (i do the same) Use a resistor of double the original value, no need to change the caps value. Example : http://www.preservationsound.com/wp-..._520_schem.jpg

[trem]

Sorry, guess I was not very clear.
This would be:
1. Fixed bias
2. Dual bias pots
3. Bias-vary trem

[defaced]

The schematic you linked to is for cathode bias. If you want separate cathode bias, then do as kleuck suggested and use separate cathode resistors.

If you want adjustable fixed bias, Paul P and Enzo worked out a dual bias schem, you can search for that. It'll be in Paul's Frankenamp build stuff. I took that work, made it into a quad bias and made a bank pot to swing the whole thing. If you search for my name and quad bias you'll find it. Both of these could be hooked up for trem vary bias with little effort if my memory is correct. I'm sure Fender made a fixed bias amp with bias trem that you could steal from, unfortunately I'm not hip to old Fender amps so I don't have a starting place to provide to you.

[exclamationmark]

Here's a thread that may be helpful. http://music-electronics-forum.com/t5415/

A dual bias supply is pretty much the same as a single bias supply, except that you need to RC filter each bias tap (so it doesn't oscillate or interact, much like decoupling the pre-amp supply). I dunno how you'd work in the bias wiggling circuit though, as I have no clue how it actually works, apart from modulating the power tube bias.

[Chuck H]

Something not being addressed as yet... The OP has no bias tap or seperate bias winding. So the dual bias would need to filch from the HV supply. I looked into this once and IIRC you'll want the supply to be capable of some current to use with a bias vary trem. I don't remember why. But I do remember that there aren't any bias circuits that filch from the HV that are suitable for this.

[trem]

Sorry, let me just reiterate.
The hand drawn is for my rectifier.
The Ampeg schem is for my PI and Trem.
As I said in my OP, I guess will have to pull the bias right from the HT secondary. Maybe like a Train Wreck Express.
I will try to use the link above for Dual Bias Supply. (thanks)
One of my biggest stumbling blocks (theory wise) is how to build the Trem Circuit. Guess I will need a Dual 250K Pot.
Thanks for the suggestions so far, and the link.
Thank You

[Raybob]

.. Guess I will need a Dual 250K Pot.
Thanks for the suggestions so far, and the link.
Thank You

Yes, I've done this using a dual 250K pot, on a Princeton circuit. Works fine. Separate the 220K resistors and send each to each of the two pots.

[defaced]

Here's a thread that may be helpful. http://music-electronics-forum.com/t5415/

Yep, that's the thread.

As I said in my OP, I guess will have to pull the bias right from the HT secondary. Maybe like a Train Wreck Express.

For a bias winding I often like to take a small filament transformer and run it backwards off the heater winding. This way what is usually the primary ends up being the winding from which the bias supply is derived. A transformer with a 8 to 10 v secondary and a 120v primary will end up at about 70 to 90v on the primary when the secondary is hooked up to the heaters.

[trem]

Thank You Everybody.
I can say with confidence...I will be back for more guidance.
I envy you guys that have degrees in Electronics/Electricity and actually know what you are doing.
I will have to remember that filament tranny trick. There is No Way i could use it in this build however, my real estate is very limited.
Thanks Again