Author Topic: Preventing pop in a Superheated SHO  (Read 1603 times)

fatfoohy

Preventing pop in a Superheated SHO
« on: August 19, 2014, 09:46:44 PM »
Long time, no post......

So I have built a Superheated SHO, and moved the Hot/Superheated switch to a footswitch instead of a toggle.  Since it's on a footswitch I'd like it to switch without a pop of course.  Would a 100uf cap going from 9 volts to the center pin of the switch, keep voltage on the circuit as it switches and eliminate the pop?



I'd like to hear some other thoughts on this before I get to tinkering.

Fatfoohy
having leftover parts is just proof that you made it better!!!!

R.G.

Re: Preventing pop in a Superheated SHO
« Reply #1 on: August 19, 2014, 10:23:59 PM »
So I have built a Superheated SHO, and moved the Hot/Superheated switch to a footswitch instead of a toggle.  Since it's on a footswitch I'd like it to switch without a pop of course.  Would a 100uf cap going from 9 volts to the center pin of the switch, keep voltage on the circuit as it switches and eliminate the pop?
It won't help. Might hurt.

This pops because the voltage on the drain of the lower FET changes when you change from a resistor load to a Mu-stage load. If this were all carefully balanced, with the cap on the mu-stage load pre-charged, and the mu-stage JFET selected to make it all work out... maybe.

In practice, it's far simpler to make two of these, one with the mu-stage load and one with the resistor load and make the footswitch switch between them. Duplicating the lower MOSFET is easier than what you'll need to do to make the single one pop free.
R.G.

Quick IQ Test: If anyone in a governmental position suspected that YOU had top-secret information on YOUR computer, how many minutes would you remain outside a jail cell?

Bill Mountain

Re: Preventing pop in a Superheated SHO
« Reply #2 on: August 20, 2014, 09:11:26 AM »
Plus with the dual circuit design you could run them in series for extra special goodness!!!

fatfoohy

Re: Preventing pop in a Superheated SHO
« Reply #3 on: August 20, 2014, 09:09:44 PM »
Hmm.......well that is truly disappointing..........

I'll have to prototype a stacked version, but for now I'm thinking I'll just build it with a toggle instead of footswitch to prevent the urge to switch it silently.

Thanks guys!

Fatfoohy
having leftover parts is just proof that you made it better!!!!