Hi All,
(https://i.postimg.cc/hfDZdcvG/Popswitch.jpg) (https://postimg.cc/hfDZdcvG)
I'm working on the above distortion circuit (simplified) with a high/low gain switch. The problem is that it makes a big old bang every time I flip the switch. I know that this is generally an issue and I found a number of different discussion on the board here, but they all refer to non-existent schematics (or that I can't find, I'm new here), so it's tough to figure out what they're talking about.
R.G.Keen has a faq posting (http://www.geofex.com/Article_Folders/box_pop.htm) that hints at the problem, but also says it's not really fixable. Basically, because I'm jumping between gain levels, the opamp is having to make non-continuous changes, which translates into a pop when the speaker tries to reproduce it. I've tried various values of capacitor in various places, thinking to use it as a super high-frequency RC filter, but no dice.
Does anyone had a fix/solution/magic bullet? I've seen reference to FET switching circuits, but haven't had the chance to research them at all yet.
Thanks in advance.
hello K_k, welcome to the forum.
hard wire your 560k resistor to the 500k pot. then switch the 110k in parallel w/ the 560k, that way you will always have the feedback loop closed, to some extent.
Short and sweet. Genius. Thank you.
p.s. I am very fond of your nickname.
IMHO, a make-before-break SPDT switch should eliminate your issue..
(it shouldn't leave no time for the op-amp to pass into open-loop gain..) :icon_wink:
Alternatively, you can connect each "open" feedback resistor leg to op-amp inverting input via a BIG resistor (1M, say) and make gain pot value 1M (instead of 500k)...
(don't bother k_k.. just a temporary mind trouble..) :icon_wink:
edit: Down-under connection is by far faster..
(both for welcome & suggestions..) :icon_redface:
Everything in series - switch jumpers either 110k or 560k:
(https://i.postimg.cc/nXMqym7Z/image.png) (https://postimg.cc/nXMqym7Z)
Quote from: antonis on July 31, 2019, 11:20:49 AMDown-under connection is by far faster..
Down-under connection?
Quote from: GGBB on August 01, 2019, 12:15:14 AM
Everything in series - switch jumpers either 110k or 560k:
(https://i.postimg.cc/nXMqym7Z/image.png) (https://postimg.cc/nXMqym7Z)
That one makes my brain go sideways. I'll cut myself some slack for not thinking of it. Cool idea, though, thanks.
Quote from: Karlsbad_kontradiction on August 02, 2019, 11:29:00 AM
Down-under connection?
It refers on mr.
duck_arse way of thinking.. :icon_wink: