SS Switch For Komet Fast Gradual

[soma_hero]

The datasheet says the mosfets have a 400V breakdown voltage with 150mA continuous load, so the voltage and current from a preamp cathode will be no sweat.

The schematic from Mark Huss site for the generic mosfet switch could be used exactly as is for switching in a cathode boost. Connect one half of the SPDT to the bypass cap, with the center connection going to ground and the bypass cap going to the outer pin of the chip, other cap leg going to the valve cathode. The other pin of the SPDT could go to another cap or leave unconnected for either boost/no boost.

[Tonegeek]

You mean like this?

Have you noticed any ill effects on the tone of the signal going through the MOSFET in the fast/gradual application? The low power version (where it appears you are blocking the DC with the .1 caps) especially looks like it would have to have some effect on the tone. I like the concept of SS switching but am stubbornly stuck on relays although granted, a relay is not a good choice in this application. Maybe the technology is good enough now to rethink my prejudice against SS switching in tube amps.

[Structo]

Yes I would like to hear more about this as well.

Since I would be switching preamp cathode capacitors in and out I'd like to know a little more about it before I buy any parts.

Thanks, Tom

[soma_hero]

The resistance of these switches is like 27 ohms. Put a 27 ohm resistor in series with your signal line and see if you can hear it.

[Tonegeek]

The resistance of these switches is like 27 ohms. Put a 27 ohm resistor in series with your signal line and see if you can hear it.

I am not sure comparing it to a resistor is valid. It looks more like you would be inserting a transistor into your signal path since the device is a MOSFET. Not sure that is a bad thing. I am curious to try it myself, but we all know what an amp full of transistors sounds like...

[marketleader]

I'm new to the SS switch usage and can't comment from firsthand experience, however since the mosfet is used as a switch rather than as a gain device and the switching is optically isolated, I would think the SS relays would be even better than standard relays in regard to minimizing any negative tonal effects. As used in the Fast/Gradual position on an Asteroid, 20 ohms should make no difference, any golden ears out there tried these and care to comment . . . Dana or Allyn?