Re: Mute Circuit Vactrol/Opto or Something else
« Reply #20 on: November 14, 2019, 10:18:55 AM »
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.

Would these work in the original schematic? If they are dual would only 1 be needed per channel? Or should I just disregard pin 4 on the VTL5c2/2
I'm still a bit confused on the important data sheet specs... Can someone recommend an appropriate and obtainable part?


abbey road d enfer

Re: Mute Circuit Vactrol/Opto or Something else
« Reply #21 on: November 14, 2019, 11:03:29 AM »
Would these work in the original schematic? If they are dual would only 1 be needed per channel?
Yes.

Quote
I'm still a bit confused on the important data sheet specs... Can someone recommend an appropriate and obtainable part?
there are two important parameters:
  • ON resistance: it conditions how you need to dimension the other elements in the circuit. The circuit is a double -L attenuator; increasing the resistors increases attenuation, but one must not look for enormous attenuation. As long as the signal is attenuated by about 100dB, you can consider it's a true Mute. Targetting a higher attenuation would make the circuit sensitive to parasitic capacitance. Actually, it's the ratio between ON and Off resistance that should matter, but for practical purposes, one can consider the Off resistance as infinite.
  • Time constants: It's the time the photresistor takes to swing from one state to the other. Shorter times will provide quicker transitions.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Re: Mute Circuit Vactrol/Opto or Something else
« Reply #22 on: November 14, 2019, 01:41:53 PM »
Yes.

"Yes" it will work in the original schematic with 2 vactrols? or Yes I'd only need one? Haha.

Thanks for clearing up some of the specs.

abbey road d enfer

Re: Mute Circuit Vactrol/Opto or Something else
« Reply #23 on: November 14, 2019, 04:11:37 PM »
"Yes" it will work in the original schematic with 2 vactrols? or Yes I'd only need one? Haha.

Thanks for clearing up some of the specs.
You only need one. The same LED illuminates both photocells. I'm referring to the implementation with two series resistors and both photocells as shunts.
« Last Edit: November 15, 2019, 04:18:13 AM by abbey road d enfer »
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

squarewave

Re: Mute Circuit Vactrol/Opto or Something else
« Reply #24 on: November 14, 2019, 07:38:40 PM »
Would these work in the original schematic? If they are dual would only 1 be needed per channel? Or should I just disregard pin 4 on the VTL5c2/2
I'm still a bit confused on the important data sheet specs... Can someone recommend an appropriate and obtainable part?
Uhhhh, no. The ESP schematic with one in series and one shunting? One would have to be on while the other is off which cannot be done with the dual element vactrols. And you cannot use dual shunt because the on resistance is too high (700R at 40mA). And vactrols will distort if the signal level is high enough. And your burning 40mA?

No. Vactrols are for compressors and that's about it.

For mute or switching I would use an analog switch. There are really high quality high voltage analog switches now that have on resistance of a few ohms (and sometimes less than an ohm) and operate on microamps. Search mouser for a high voltage dual analog switch and do a series / shunt circuit.
« Last Edit: November 14, 2019, 07:48:09 PM by squarewave »

Re: Mute Circuit Vactrol/Opto or Something else
« Reply #25 on: November 14, 2019, 09:14:06 PM »
> 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.

Must be a simulation issue for me then. I'll just breadboard it up and see how it goes.

Rocinante

Re: Mute Circuit Vactrol/Opto or Something else
« Reply #26 on: November 16, 2019, 05:14:31 PM »
I used this in several guitar amps

If there's a harder way to do this, I haven't found it yet.


 

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