Cathodyne gain calculator link

[slideman82]

I think there was a cathodyne gain calculator placed at this link Audio Amateur Incorporated but it seems it's not, now, but I can't remember if it was there or somewhere else. Did anyone see this? I'm interested on ballancing cathodyne ouputs.

 

[aardvarkash10]

was it this one?

 

[TonyTecson]

afaik, you can treat the cathodyne as a unity gain amp.....

 

[slideman82]

Yes, that's right... but I'm interested on ballancing outputs, depending on tube and resistores I'm using it.

 

[slideman82]

was it this one?

Yeeaah! That could help, I think! Tell ya later

 

[TonyTecson]

Yes, that's right... but I'm interested on ballancing outputs, depending on tube and resistores I'm using it.

just like the common cathode, you half the plate load resistor to get 2 equal valued resistors, the circuit is inherently balanced....
look here: The Valve Wizard

 

[DF96]

Why use a calculator? Gain =1 (actually just below, but close), balance comes from identical loads at each output port. What is there to calculate? (Apart from load lines etc, which are done graphically anyway).

 

[slideman82]

Just want to ballance outputs the best I could, although this is just theory... That XLS file could help, but I think I can't modify any parameter... and I'm not going to use an ECC99.

 

[SY]

Just want to ballance outputs the best I could

Use matched plate and cathode resistors, then matched grid leak resistors in the next stage. Done, you're in perfect balance.

 

[slideman82]

But cathodyne output it will still be unbalanced... I'm using cathode bias resistor, too

 

[SY]

If plate and cathode loads are matched, you're balanced.

 

[slideman82]

So, I'd have to match grid bias resistors, and...?

 

[TonyTecson]

just do it and don't overload your cathodyne for trouble free operattion....

 

[slideman82]

What do you mean by don't overload it?

 

[aardvarkash10]

don't try and draw more current than the weakest output can deliver...

 

[SY]

So, I'd have to match grid bias resistors, and...?

Match cathode and plate resistors of the cathodyne and the grid leak resistors of the stage it's driving. That's it.

 

[DF96]

But cathodyne output it will still be unbalanced... I'm using cathode bias resistor, too

Show us your circuit. If you are using an AC-coupled cathodyne you can still ensure perfect balance.

 

[slideman82]

It's a tipical Fender-style cathodyne phase inverter, 56k plate and cathode resistors (metalfilm 1%), 1.5k cathode bias resistor (mf 1%), probably a switch for a 1.5k bypass cap. Grid bias resistors are 220k, coupling caps 22n. Output tubes are EL34, 30W output.

 

[DF96]

If you take one output from 56K to ground, and the other output from 56K to HT+ supply, and apply equal load, then they are guaranteed to be balanced.

Bypassing cathode bias resistor (or not) will affect gain and LF frequency response by a tiny amount, but will not affect balance. HT+ decoupling arrangements may affect LF balance, but you just have to ensure that you use the right values to maintain balance to as low as you need. If this is a guitar amp then fine details of output stage balance probably don't matter anyway.

I'm not sure what the problem is. We keep saying that exact component balance guarantees exact signal balance (not true for most other phase splitters BTW) but you seem to have trouble believing us?

 

[TheGimp]

The only time you have an imbalance is when you drive it into grid current which upsets the balance.

No grid current - balanced operation given equal load impedance.