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paulb 27th December 2001 03:52 PM

Muting: alernatives to mechanical relay?
I'd like to mute 6 channels of audio for about 10 seconds at power-on without having a 2 or 3 electromechanical relays. I plan to short the output for this duration. Has anybody seen or used something like analog switches (e.g. 4066 or higher quality versions) to do muting?
Thanks in advance for your suggestions.

Geoff 27th December 2001 04:01 PM


In one of his MOSFET amps, JLH used a simple FET clamp circuit at the input to provide a mute delay. I can send you details if this is of interest.


paulb 27th December 2001 04:40 PM

Thanks, Geoff, that's probably along the lines of what I'm looking for.
Is it in one of the schematics on your site?

Geoff 27th December 2001 04:47 PM


No, sorry it's not on my site (the amp's both MOSFET and Class-B). email me and I will reply with an attachment containing the relevant section of the article.


PH104 27th December 2001 08:20 PM

Analog optocouplers are also nice depending on your needs - about $3 ea. from Allied. For audio application notes see:


richt 27th December 2001 08:49 PM

merry christmas to this forum!

i highly recommend to use relays for muting!!!!!!!

by my experience solid states devices tends to alter in any
manner the audio,specially hi-end systems!

last week i modified my cd player eliminating the transistorizied muting & emphasis circuitry with relays (difference was huge)

if u are still interested with transistors ,let me know & tell you
how was configured my player.

or stick to digikey catalog that they have very good realys
ex. 8 contacts in one only package)

thank you

paulb 28th December 2001 01:11 AM

Those Silonex optcoupled variable resistors look great. Little pricey.
I may try the JLH circuit that Geoff sent me (thanks, Geoff). But I also did find some 4PDT relays in my junkbox that will probably work for now.
Thanks for your suggestions, folks.

GRollins 28th December 2001 06:06 AM

For those who are lazy, Potter & Brumfeld used to (probably still do) have relays that you buy off the shelf with set time delays.
When I bother with such things, I use an antique idea based on a unijunction transistor that triggers an SCR that triggers a relay. Unijunctions are worse than hens' teeth now for availability, so the next time I do something of that nature, I'll probably use something like a 555 timer to trigger the SCR. Not all that difficult to do.
Nelson burns off out-of-spec MOSFETs (at least I assume they didn't make the cut, it's what I'd do in his position to keep costs down) in a cute little one-two punch to trigger a relay. Check out the...duh, I forgot...maybe the Aleph Ono schematic, I think. Couple of resistors, couple of diodes, couple of MOSFETs and a cap. Nuthin' to it.
I've seen lots of variations on the resistor & cap time constant to the base/gate of a transistor to do a solid state mute here and there, but for the life of me can't remember where I saw the last one. If my memory unclogs, I'll post a link.


PH104 28th December 2001 04:46 PM


Thanks for the tip on the relay + delay on the Aleph Ono -- that is cute! I wish I had seen it earlier. I'm building 555-delayed relays for soft-starts for Parasound 3500s but the Pass MOSFET circuit would have given me a lot more flexibility in where I pick off the power for the delay circuit.

Thanks again


paulb 28th December 2001 05:42 PM


Originally posted by GRollins
For those who are lazy...
You talkin' to me?

Seriously, I've discovered the 4541 CMOS circuit for any time delay stuff and won't go back to 555s or anything else. Datasheet's a bit opaque but the part itself is versatile and accurate. I'll probably use it for this application with a cheap TIP14x Darlington transistor to drive the relay.

Check it out:

Hey, being lazy is good engineering practice, it involves thinking before doing...

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