Switching question

[Hellhammer]

Hello,
First post and I have a question. I'm building a Hiwatt inspired amp using a multi-tap PT and 4x6v6GT power amp. I want to keep the screens at the lower voltage tap whilst being able to switch Plate and pre amp voltages. I know switches aren't very good at handling high voltage DC but most amps have the standby switch after the rectifier anyway. And switching while on standby should be ok right? This is my plan.. shoot it down if it's crazy.


[img:800:520]http://i94.photobucket.com/albums/l96/s ... tapalt.gif[/img]

[Alexo]

Looks good to me, I've done something very similar and all is well. The only potentially wonky aspect is that when you switch to the lower voltage taps, you will have some power reserve coming off the filter caps at a higher voltage than is coming off the rectifier, but this shouldn't really cause any issues.

I would maybe rework the switching on the bias so that in low voltage mode, it throws that smaller R in parallel with the larger one, that way, you'll eliminate any risk of running without a bias supply for an instant as you flip the switch.

If you are worried about that high of a voltage on the switch, you can browse around allied or mouser and find higher rated switches than the standard mains switch, but as you say, if it's good enough for a standby switch....

..and though I did the same thing on one of my amps, sorta, switching between HV taps/SS rectifier and the output of low voltage taps into a tube rect, I'm still a little scared to throw that switch while the amp is running!

[Hellhammer]

Looks good to me, I've done something very similar and all is well. The only potentially wonky aspect is that when you switch to the lower voltage taps, you will have some power reserve coming off the filter caps at a higher voltage than is coming off the rectifier, but this shouldn't really cause any issues.

I would maybe rework the switching on the bias so that in low voltage mode, it throws that smaller R in parallel with the larger one, that way, you'll eliminate any risk of running without a bias supply for an instant as you flip the switch.

If you are worried about that high of a voltage on the switch, you can browse around allied or mouser and find higher rated switches than the standard mains switch, but as you say, if it's good enough for a standby switch....

..and though I did the same thing on one of my amps, sorta, switching between HV taps/SS rectifier and the output of low voltage taps into a tube rect, I'm still a little scared to throw that switch while the amp is running!

Thank you! I was actually going to to the bias like you suggested, just hadn't updated the schematic. The amp is for a friend so I'll put the switches on the back to reduce the risk of switching while the amp is running.