Switching Plate Load

[Colonel_Sanders]

I'm not sure either . I think I'm trying to calculate the maximum voltage swing across the plate load.

According to my multimeter, my laptop is putting out 270mVAC. In the first gain stage I measure a drop of 102VDC across the 100K plate load. From the plate load to ground I measure about 17VAC pk to pk which gives the stage a gain of around 60.

B+ for V1a is 370VDC. That means the maximum voltage swing will be from 285VDC to 251VDC. As tbyranh said earlier, a boost pedal might have a gain of 10 = 2.7VAC input which means the signal swing could be about
370VDC to 106VDC, worst case scenario.

So the switch/vactrol would have to rated for 264VDC.

Does this sound about right?

[Colonel_Sanders]

BTW, there are a couple of Vactrols with a cell voltage of 300V and one with a 500V rating.

http://www.ortodoxism.ro/datasheets/...lmer/VT500.pdf

Cheers,
C_S

[Colonel_Sanders]

Well I just bought a couple of VTL5C6's (250V cell voltage) to try out. On resistance is 2K @ 40mA and off R is 10M. I was thinking about using it as the parrallel resistor, but I reckon I'll just use it as a switch.

Thanks heaps for all your help guys. This forum is stonkin'.

Cheers,
C_S

[Gregg]

So, any ideas on how to tame the pop?

The only way to avoid poping is to use some sort of "smart" type of switching. You can find such switching in Peavey amps - the so called clamping where a triac is used.
In my amps/preamps all relays are connected to a PIC12F629 /or 16F690 if there's more to switch/ which via relay shorts the sound to ground for 50-60ms while the relays are switching thus avoiding any poping.

[Enzo]

That mutes the amp briefly when channel switching, but many guys object to the "delay" it causes. That momentary blank in the sound bugs them.

[Gregg]

That mutes the amp briefly when channel switching, but many guys object to the "delay" it causes. That momentary blank in the sound bugs them.

That's entirely their problem. I don't object even a 100ms delay if completely noiseless switching is desired. Unfortunately in such cases there's always a compromise to be made.