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Vintage threads from the first ten years

Re: placement of a standby switch

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1/1/2000 7:50 PM

Mark Buckingham

Re: placement of a standby switch

quote:
"
That resistor and the bias supply's filer cap form an RC circuit with a long time constant.
"

That makes sense. I've used cathode biasing on all the amps I've built so far, so I really haven't had any problems. The next amp is going to be fixed bias though.

12/30/1999 1:06 AM
Nils	Hi, The Matchless Chieftain is using the ct/stby switch acc to the schematic, but I've never seen one in the flesh. Nils

1/1/2000 3:31 PM

Why don't you use a switch to open the cathodes of the output tubes? B+ stays on, bias stays on, and one side of the switch stays at ground potential.

It's even easier if you use a power MOSFET like the IRF820 or better to switch the cathodes. The MOSFET is designed to switch DC loads in the B+ range and can be controlled by a small switch to ground on the gate.

The MOSFET saturates to under 1 ohm, and adds no change or coloration to the tone of the amp.

1/1/2000 7:47 PM
Benjamin Fargen	R.G. That would work great for a fixed bias design........but he is building a cathode biased 5E3 deluxe clone. details... details Take care, Benjamin.

1/1/2000 9:01 PM
Steve A.	Benjamin: Maybe I'm missing something here, but wouldn't R.G.'s idea work roughly the same with a cathode biased amp? Steve Ahola

1/1/2000 11:05 PM
Pete Cage	I use the cathode standby on all of my amps (both fixed- and cathode-biased) and it works very well. I'd guess that it's easier on the switch, too. Best, Pete

1/2/2000 3:54 AM
Benjamin Fargen	retraction! Steve, R.G., Looks like I'm the one whose missing something!!!!I misread R.G.'s response ........My bad..... sorry about that. I should have known better........R.G. never makes a mistake! I wish I could say the same! Benjamin.

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