Removing an audible “pop” from a CMOS switch - Ramping Power?

Thread Starter

danalog

Joined May 8, 2012
19
here's another thought.....Something I had in mind for future project of some kind

I will be using hermetically sealed relays specially made for audio switching.
I have seen this and I think it is much better than any other switch
I would like to see that when you have it ready!
 

bertus

Joined Apr 5, 2008
22,270
Hello,

The effect on the tone will depend on the value of the capacitor and the value of the resistors.
The circuit makes a highpass filter like on this page: High-pass filters

As fro the resistor values, it depends on de driving capacity of the incomming circuit.
In case of 10K the driving circuit will see 5K (2 X 10K parallel) when the switch is open and 2.5K (4 X 10K parallel) when the switch is closed.

Bertus
 

R!f@@

Joined Apr 2, 2009
9,918
Bertus, I knew what bertus showed was a filter
If the RC combination filters, OP should listen and see if he hears any difference in the sound reproduced. Specially in the lower range.
If u are satisfied then bertus method should be fine.

The relay method has a lot of advantages u know.
No noise.
No signal loss what so ever.
No cross talk between the channels.
 

rogs

Joined Aug 28, 2009
279
Thank you Bertus, I tried this with 10k resistors and your tip immediately killed the pop in the switch!

What would be the difference in the circuit in respect to going lower with the 10k's or going higher as in the 100k's? I have tried them both and cannot tell an audible difference in the sounds overall tone or volume.
I was thinking that changing the size of the resistors would have changed the tone some, but now I am thinking that outside of balancing the DC level that the resistors do not color the sound. Is that a correct assumption?
You did say in your earlier posts that you wanted 'flawless' silent, transparent switching. I see you are happy to just accept a significant reduction in the pops, by using DC control of the switch inputs and outputs I mentioned in my earlier posts, rather than completely silent switching.

That will allow you to use the 4066 then.

Keep the value of the resistors high. Certainly 100K - preferably even higher.

Making them too low will load the very high output impedance of your guitar pick up, effectively 'damping' it's output a little, and slighlty reducing the high freqenecy response and sustain.
Not a lot --but you did say you wanted a 'transparent' signal path!

As it would appear that you are happy to accept some compromise, there are of course lots more options open to you now.....
 

Thread Starter

danalog

Joined May 8, 2012
19
I may have over reacted because his suggestion killed the "pop" that was the first suggestion that removed it. I wasn't thinking about the entire sound spectrum and didn't think to check the response across the entire range.
Times like this I wish I had an oscilloscope!

However, using the resistors didn't just reduce the "pop" it totally removed it... IF... I also removed the 2.2 Non Polar electrolytics that were added per your suggestion. That made me start to wonder if I had a solution or just a good start.

I know that using IC's is better on the sound than using a DPDT switch or FET switching, and a quick search of guitar DIY sites will show that many agree with me. Relays are nice and quiet (yet a tad pricey) and can fail over time. That is what has kept me from going the relay route.

That said -

I have also been learning that CMOS chips like the 4066 are a bit fragile and I could be setting myself up for a failure this way as well.

I am still very interested in using optoisolators and am also reconsidering relays too.

Help, I DO want this switching system to be transparent and bulletproof, yet cost effective.

Thoughts????
 
Last edited:
Top