Noiseless optical bypass

[rullywowr]

The Voodoo labs optical bypass is quite trick, as is Josh's (1776) take on it with the Optostomp PCB.  I keep thinking how to make the footprint smaller of the PCB, and also lower the cost of the components.  I envision a DPDT with a small array of 0603 or 0805 resistors, capacitor, and SMT S1KB diode for voltage protection.

I am wondering if a small SMT SSR such as the IXYS CPC1017N would work.  "It is a Single-Pole, Normally Open 4-Lead SOP OptoMOS® Relay" and goes for around $0.40.  Datasheet here: http://www.mouser.com/ds/2/205/CPC1017N-16278.pdf.  On resistance is around 16R, which is even better than the H11F1M.  The on/off time is around 10mS which would be slower than the H11F1M however should be negligible.

When studying the CPC1017N datasheet, I am unclear on what the maximum voltage would be for the CPC1017N?  Since there is a LED used as the emitter, there has to be a limit on how much it can take.  It would be lit up in series with another LED (the effects LED on/off indicator) as well as a CLR.  It says the typical forward voltage drop is around 1.21v.

Since the typical H11F1 is also FET based, I am hoping that something like this would suffice in its place.  Any input would be greatly appreciated.  I plan on experimenting with it to see how it can perform in a audio switching application like bypass switching of effects.

[midwayfair]

The on/off time is around 10mS which would be slower than the H11F1M however should be negligible.

I have to kinda disagree here. The human ear can detect about .5ms of latency, and 10mS is enough to be perceived as "delay." The H11F1 is 25 MICRO seconds. It's 400 times faster! I realize that we probably deal with 10mS pretty often in digital recording without being too bothered, but I feel like you need a more compelling reason to put up with the poorer switching performance than saving a dollar on the chip when you're dealing with a latency that eventually you or someone else will be able to hear and will be bothered by. The H11F1 SMT is a little cheaper than the DIP package, too.

The good news is that there's no reason you can't make a board that could handle either, and then you could test them both. The pinouts are the same between all the optoisolator chips.

You should be safe going from 9V to 18V with the same CLR. If you were dealing with 30V or something, it might be worth worrying about. There should be some fudge room in your CLR regardless.

Oh, also, you need to worry about potential static protection with a CMOS chip, just like with MOSFETs, clock chips, companders ... and all those other components that blow up all the time. So you'll need an overvoltage zener at the input (which can also be a crude voltage regulator).

Where I would think about using these as a switch is in applications where an immediate on/off might produce a thump or scratching sound, like passive bias adjustment boosts. The question there is whether there aren't already better ways to handle such things.