Loud gain switch

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jrmintz

Well-known member
Joined
Jun 4, 2004
Messages
998
Location
NY
Hi all,

Why would the gain switch on a mic preamp click very loudly (electronically) when switching positions?

Thanks,
 
I have a lot of break before make switches where I have this problem, is there a remedy for this, or just something to live with?

dave
 
for some reason the MBB greyhills are special order at digikey and elsewhere, which is a major drag... It would be nice if there was a fix using the bbm switch as thats the part most commonly available here.

grumble grumble....

dave
 
what about putting a resistor in parallel with the switch? you'd have to refigure your values, but when the swich is going open in between positions the FB loop is seeing the parallel resistor.
 
Thanks guys,

I don't want to reconfigure the resistors on the switch - life is too short. :green:

I can live with it if I have to, I guess.

:thumb: :thumb:
 
[quote author="al_p"]what about putting a resistor in parallel with the switch? you'd have to refigure your values, but when the swich is going open in between positions the FB loop is seeing the parallel resistor.[/quote]

Hmm... That's an interesting idea. I guess it wouldn't work with most Neve style switches (caps as well as resistors). I'm gonna think about this for a while!

Ian
 
would that work? I get a pop on the gain switch on my 312, and the circuit already has a fixed resistor already present in the feedback loop, so in theory, when the switch is between positions, its as if the switch wasnt there at all, right? Still pops...

That sounds like it should work though.

dave
 
Wouldn't putting an extra FB resistor across the entire switch pad the FB loop? It would just lower the ceiling of the pop...I think.
 
If you make the parallel resistor 10 times the value of the highest total resistance of the resistor string, then it will have little effect on operation. This will probably not eliminate pop, but could minimize it.

MBB switches up to 12 positions were readily available last time I checked.
 
from who dave? I tried to find the greyhills and they seem to be special order from the usual suspects.

dave
 
I dont like those lorlins, cheap plasticy feel to them. Are the alphas any better? Cant argue with the price though, the greyhills are like $15 each.

dave
 
The Alphas are your typical utility-grade phenolic-wafer open-frame switch. They do the job and have a pretty solid feel to them. I've used them in some projects and have had no reason to complain.

Being open frame, the contacts require cleaning eventually. Actually, this is true of all rotaries; it's just that the open-frame types usually require cleaning sooner. Luckily, they're also a lot easier to clean!
 
Gus told me about the Alphas not too long ago. I think Mouser had just started selling them. They not only have a more solid "feel" than the Lorlins, but also seem to have way better contacts as well. Pry open a Lorlin and compare it's contacts to the Alpha's and you'll see what I mean. I believe the Alphas are the same ones you get at Radio Shack. If so, I have some really old ones (mid '80s) that are still working great.
 
Digikey sells CTS 11-position rotary switches that are very good - much better than Lorlin, and about $9.00 IIRC.
 

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