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Vintage threads from the first ten years

Re: Soft start power supply?

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5/31/2000 11:08 PM
Ken Gilbert	Re: Soft start power supply? you made me laugh out loud at that one, rg! kg

6/3/2000 11:08 PM
Stephen Conner	Don't laugh! I quite like my regulated B+. The three mosfets have a certain Zen-like beauty to them. And I beat R.G. to it, I already have soft-start, foldback current limiting, and shutdown on bias failure or excessive screen current. No idea what it does to the tone though, probably nothing. But it sure doesn't hum. Steve C.

6/1/2000 7:00 PM

Chris,

Here's an exerpt from the Glass Audio article (I hope I don't get in trouble by typing this without permission...)

This discussion references using a 6X4 rectifier.

"If the 6X4 can safely pass the amplifier's total current draw, one possible solution is to insert the 6X4 between the transformer's center-tap connection and ground. This way, there would be only a few volts difference between the heater and the cathode, and the whole high-voltage line would experience a soft-start.

The limiting factor is how much extra load the existing heater winding can tolerate. The nice feature about the 6X4 is that its own heater draws a very low 0.3A. Adding this tube to an existing heater string would probably not tax the winding. If your heater winding can tolerate greater loads, then choose a rectifier tube with greater plate current capabilities."

I think this is a good idea though I haven't used it myself. I already have soft-start capability in using a GZ34/5AR4 rectifier.

One thing to consider is the voltage drop across the inserted rectifier. It may/may not significantly reduced the available B+.

Later,

DJ

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