PT for 6550!! voltage and current!!

[grtamp]

Hi , I want build a new amp with 4x6550 power tubes , what type of PT can I use?
360-0-360Vac secondary with 400mA is sufficient?
For bias tap 60Vac?

Thanks

[Phil_S]

You really should look up the tube data and decide for your self. It's fairly easy to do. Here: http://tubedata.itchurch.org/sheets61.html I looked up the Tung Sol, which gives typical operating conditions PP AB1, at 450VDC and 600VDC plates, fixed bias. At 450, max signal plate plus max signal grid 2 = 333mA per pair. At 600, max signal plate plus max signal grid 2 = 303mA per pair. You want a quad? It's double. Is 400mA enough?

Current requirement goes up as plate voltage goes down. Using 360-0-360, your plate voltage will depend on rectifier choice, anywhere from about 360*1.1x to 360*1.4x.

Tapping the HT output before the rectifier shouldn't be a problem once you find the right PT.

[Roe]

watch the screes voltage. you may need a dual rail power supply if you go for higher plate voltages

[grtamp]

Hi , I thought to run with about 500Vdc on the plate (no tube rectifier) , in this case I should need to dual power supply for screen grid?

[cobalt]

hello,

have you seen this?
http://www.hammondmfg.com/pdf/EDB379WX.pdf
In theory, you could run a sextet of kt88 or 6550.
Just sayin'.

weirddave

[grtamp]

maybe this is a too big PT!!!! 1A and 12A for heater is too much!! i want run with 4 and not 6 power tube!

[Roe]

Hi , I thought to run with about 500Vdc on the plate (no tube rectifier) , in this case I should need to dual power supply for screen grid?

screens voltage shouldn't exceed 440v unless you're using kt88s. so you need to drop the screen voltage about 60v

[grtamp]

Maybe this can be my ideal PT

primary: 220 - 230 Vac

secondary 380-260-0-260-380Vac @ 700mA (for plate and screen grid PS)

HT: 3.15-0-3.15 Vac @ 7.5A

Bias supply: 60 Vac

[grtamp]

this ideal PT , can be ok?

[Phil_S]

this ideal PT , can be ok?

Impossible to say without knowing the circuit. I think the best anyone can offer it that it seems reasonable. Ideal? Can't say.

[grtamp]

I thought 4x6550 drived by CF stage with 12BH7 ( like ampeg amp) , about pre amp I thought a classic Fender twin.