What is the simplest way to generate two separate -ve grid bias voltage

[Alan0354]

I interpret Antek's statement to mean that you can safely get 480VA total from a "400VA" unit at 60Hz, and 120% of the nominal current rating for any one winding, but I suggest you confirm this with Antek. A little extra voltage loss should be expected with overload.

Stancor and Hammond publish formulas for AC secondary current given DC load current and rectifier form. They differ somewhat. You might try the free PSUD simulator for a better estimate.

I have written to Antek already, I suspect I won't hear from them until Monday. The question now is how low will the 6.3V be being overloaded 20%. Will that hurt the performance of the tubes.

 

[GordonW]

A simple 24v control transformer, with a voltage doubler, will give about 55-60VDC .

Those things are dirt cheap, and plentiful. One example:

http://www.packardonline.com/Shop/Product/5716

Regards,
Gordon.

 

[mike567]

Dont overlook old doorbell transformers you might have laying around for bias transformers

 

[Alan0354]

I decided to go back to one power supply design to feed both channels, the -ve bias is not an issue anymore, My only problem left is whether I can get away without having to buy an extra 6.3V transformer.

It is harder than people think, most of the transformers now a days are PCB mounted, very few have wire leads. I am really tempted to buy a +5V switching power supply, adjust it up to 6V and use it.

Is it because people don't use transformers now a days, I could swear it's so easy to find transformers back in the days when I was playing music and most came with wire leads.

 

[GordonW]

The transformers I mentioned- being made for home heating and cooling, and as such, to be mounted to the metal chassis of say, a furnace or AC unit- are all standard-mount transformers with wire leads. Other than possible size issues (they are like 2" on a side), they'd be easy to incorporate.

Regards,
Gordon.

 

[nj pheonix]

I have a bunch of these
(a side effect of work)

 

[s-petersen]

It looks like one I replaced on a direct vent gas heater for a freind.