Mute Circuit Vactrol/Opto or Something else

[RSRecords]

I need a noise free, pop free mute circuit. I've been investigating FET circuits as well as opto-isolator/Vactrol circuits. I can't seem to find a starting place for a vactrol circuit which seems to be the best option. It's a stereo unit. So I would think that could complicate things maybe? Any suggestions?

I searched the forum as well and found very little.

 

[RSRecords]

Found this circuit on ESP with a quick run down of how it works. Seems fairly straight forward...Any thoughts on it. I'll probably just breadboard it and see.

 

[Gold]

I remember Silonex had a good selection of app notes. It looks like the company no longer exists but was bought by someone. I didn’t dig around on the new site. Maybe the app notes are there or the way back machine can find them?

 

[Rocinante]

I made that esp mute circuit for a Mon ctrl and it worked great. Another resource is using the same layout they use for relay controlled foot pedals.
https://www.coda-effects.com/2016/04/relay-bypass-conception-and-relay.html?m=1

 

[RSRecords]

I made that esp mute circuit for a Mon ctrl and it worked great. Another resource is using the same layout they use for relay controlled foot pedals.
https://www.coda-effects.com/2016/04/relay-bypass-conception-and-relay.html?m=1

Awesome, yeah it seemed like it would work but couldn’t find any support to back that up. What did you use for the LDR. Premade or did you roll your own? I was thinking the Vactrol vtc-5c4. I think I can find them....

 

[Martin Griffith]

Farnell stocks these http://www.farnell.com/datasheets/16352.pdf NSL32, 500R on resistance, which should be OK. I might layout a simple double sided PCB, with through hole components if anybody is interested. It shouldn't take too long. Any suggested maximum size?

 

[RSRecords]

Farnell stocks these http://www.farnell.com/datasheets/16352.pdf NSL32, 500R on resistance, which should be OK. I might layout a simple double sided PCB, with through hole components if anybody is interested. It shouldn't take too long. Any suggested maximum size?

I very quickly drew it up in eagle and it measured 1.2" x 1" so it can be rather small. It probably hang off a decent panel mount switch. I'm unfortunately working this into a larger pcb project so a pcb wouldn't help outside of experimenting.

I'm not sure which characteristics are important in the datasheet. 500 msec until 100k seems slow to me but like I said I'm unfamiliar as to how that correlates in a real life muting experience. That could be fine.

 

[Rochey]

I'm curious, you say you researched the FET circuits. Is there something wrong with them?

Doug Self's book has some pretty good ones that use a T style - series in, shunt to ground, series out.

Assuming you have some kind of high impedance buffer afterwards, it should be good, no?

 

[RSRecords]

I'm curious, you say you researched the FET circuits. Is there something wrong with them?

Doug Self's book has some pretty good ones that use a T style - series in, shunt to ground, series out.

Assuming you have some kind of high impedance buffer afterwards, it should be good, no?

Yea, should be.. just exploring other options. It maybe followed by a that balanced line driver which has about a 5k input...I think...

 

[abbey road d enfer]

I'm curious, you say you researched the FET circuits. Is there something wrong with them?

Control-voltage feedthrough, THD and timing management. It takes time to optimize. Optocouplers are no-brainers.

 

[Rocinante]

I'm lucky and found a electronics shop nearby that had the vtc-54s and bought a bunch of them.

 

[RSRecords]

I'm lucky and found a electronics shop nearby that had the vtc-54s and bought a bunch of them.

Got any left? Could definitely use 4 or 5. I found some Macron brand at small bear. No idea if they are any good. Any idea?http://smallbear-electronics.mybigcommerce.com/photocouplers-macron-mi1210clx-series/

 

[Gold]

I just got 50pcs of VTL5C2/2's the other day. I have eight channels of DAOC that they are for. I'm keeping about half of them but will put the rest up in the Black Market after I have everything built and tested. Yesterday I matched them up. I used 2.5VDC as +10-12dBu is where the threshold will mostly be used. Out of 50 most fell into  80mA, 85mA or 90mA piles. There were about five outliers. The 90mA pile was the biggest so I'll keep those for the DAOC's.

 

[Rocinante]

Another great mute circuit is the 555 that esp explains here

https://sound-au.com/articles/555-timer.htm

I built an eight channel switching system using opto isolators and multiplex IC's that is silent as well. Opto with relay works great.

 

[trashcanman]

I'd like to hijack this thread with a related question. I'm figuring out a mute circuit for channels on an active summing mixer. Inputs would coming from from an audio interface or a tape machine, unbalanced.
I been trying to simulate a few and can't seem to get them to work. For example this one

Below is the schematic in Multisim.

Flipping the switch does not affect the volume of the sine at all. I'm guessing this is due to how I'm simulating it but I can't figure out why. Do I need to add the rest of the circuit before and after this stage? I was intending to put one of these on each channel when it enters the summer and after this it would go into a Lawo DV275 summing amp module. Is this even possible with this type of circuit?


EDIT: I've since found out that Multisim doesn't include simulation models for their JFETs so that explains why it didn't work.

 

[Rocinante]

I never did that circuit. But I have done many of ESP's other mute circuits with perfect results. What I really liked about them is that you can use momentary switches with them so you can access them from several different points e.g. a push button switch on the front panel and a footswitch.

 

[abbey road d enfer]

Another great mute circuit is the 555 that esp explains here

https://sound-au.com/articles/555-timer.htm

I built an eight channel switching system using opto isolators and multiplex IC's that is silent as well. Opto with relay works great.

The 555 is a timer; how do you turn it into an audio switch?

 

[Bo Deadly]

Maybe the simulation isn't running long enough to discharge the cap. Run longer ...

 

[abbey road d enfer]

Flipping the switch does not affect the volume of the sine at all. I'm guessing this is due to how I'm simulating it but I can't figure out why.

Simulation works perfectly in LTspice.

Do I need to add the rest of the circuit before and after this stage?

No.

 

[PRR]

> Flipping the switch does not affect the volume of the sine at all.

Bad simulated solder-joint?

Works for me, simplified to essentials. My Spice does not know space-bar, I put a timed switch. In the first mS the JFET is biased -4V (off) and output is nearly same-as input. At 1mS the 4V is taken off, gate capacitance is negligible, we get a greatly reduced output.