Switching on the fly

[studiodunn]

I've been playing around with NFB and Cold Clipper values and would like to implement them into an amp using these neat little boards I got fro Osh park - https://www.oshpark.com/shared_projects/vgc0JhM3

Question 1) can either the NFB or Cold Clipper values be switched with the amp running?
And thinking about this Question 2 came to mind)
I know a pot can be used for NFB. i've seen it called Focus before, but could a 50 kpot in series with an 820ohm resistor be used to adjust the cold clipper as well?

A pot would seem to eliminate the momentary disconnect and eliminate any popping that comes from switching values.

[Orson Maxwell]

Basic rule of switching: don't switch DC. That includes plate supplies, cathodes (incl. NFB) etc.

I assume that the cold clipper is the stage with a large cathode resistance. If you want to make it switchable/variable, you'll have to live with the noise - either popping of the relay/switch or the crackling of the pot. The pot won't be happy having constant DC flowing through it either - it can then come back to bite you.

You can try and arrange a fixed bias for the stage in question similar to an output fixed biasing arrangement.

You can do some smart switching if you blank the popping noise - that is if you mute the amp first, switch whatever, and then unmute it again. Never done that, but it seems like an option, although not really a simple one.

[xtian]

A pot in gNFB loop is functionally fine. And we commonly use switches in preamp cathodes with no problems.

[studiodunn]

Thank you both for the input.

The SP3T switch had far less pop than the Rotary switch. The rotary however gives an amazing range of from light crunch to High gain using 820, 1.5, 2.7, 4.7, 10, 20 and 33.

For the NFB i just used the polarity switch( Old bassman) and wired a 100 / 5m / 39 in. Seems to be a good usable range.

Pics and Schematic coming, but after a ton of experimenting I finally have the OD channel in a really good place.

[Reeltarded]

If you are swapping cathodes with a rotary it barely makes a nothing if you parallel lower and lower values over a constant high value.. you could also limit a 50k pot and dial that stage in continuously.

[studiodunn]

If you are swapping cathodes with a rotary it barely makes a nothing if you parallel lower and lower values over a constant high value.. you could also limit a 50k pot and dial that stage in continuously.

I am using it to switch in and out a single resistor on the 3rd stage cathode. After the initial experimenting with switching values on the fly I have a pretty good idea of where I want to be for different guitars and sounds. I think I can avoid live switching for the most part and as long as it isn’t bad for the amp, I think it will work. I may try a pot as well, but it’s on the back of a fender chassis and hard to see. There is a pretty significant jump in od levels, so I’m thinking the rotary switch will be good for repetition.