Good deal from Goldmine on Optocouplers (Nov 3, 2021)

[Toy Sun]

I have no idea if these are going to work for anything, but at this price, why not?
https://www.goldmine-elec-products.com/prodinfo.asp?number=G15396D

Price is $2.95 for 12

From the site:
Tiny audio optocoupler is about the size of a pencil eraser and has 4 leads. These are used extensively in audio compressors, audio level controls, audio limiters, expanders/noise gates, guitar tremolo effects, guitar amplifiers and music effect boxes. Inside the black epoxy case is a 2 lead CDS cell (not a photodiode or photo-transistor) and a 2 lead LED. This is why the device finds extensive use in audio applications (photocell instead of photodiode). The LED requires about 10-16mA current and the resistance of the CDS cell varies from 150K up to megohms when the LED is off to under 400Ω when the LED is on. New. NOTE: Dot on case marks the cathode (-) lead of the LED. Blowout price! Actual brand may vary from picture. Sold in a package of 12.

[Kevin Mitchell]

That's awfully cheap. "150k to megaohms" for off resistance is a very wide rage of variance. Heaven forbid you need a couple close in spec.
Probably better off rolling your own in comparison. Just my opinion. Thanks for sharing the link!

[PRR]

LDR offness is a lot about how long you can wait. It never stops rising.

I've never seen an audio application which really depended on the >100K response. Usually an OFF LDR is mixed with an ON LDR (1K), or IAC a few-K fixed resistor. Take LA3a which runs 68K into an opto. If the opto was as low as 150K it could be a 3dB loss, but that is instantly compensated by trimming the level control for proper levels.

Anyway-- 25 cents each?? Experimenter's delight.

[amz-fx]

It is the turn-on time that can be a problem in some of these unknown optos.  The Silonex NSL-32 will switch-on in about 3.5ms, and that is quite fast - good enough for a compressor. Other photo-resistors have a much slower response. Unknown photocells are.... unknown. No problem for a tremolo but you would have to test them for comp or limiter use.

Back in the late 1990s when I was doing some work with Tom Henry, he bought a big stash of CLM6000 optos from a surplus outfit like Goldmine. When I built the prototype compressor and tested it, the circuit worked just fine. When he built it, the response was terrible... until I sent him one of my CLM6000s to try. It turned out that I was using new CLMs from Allied and he was using the surplus parts. They were rejects/floor sweepings and he had to sort them all to get the good ones...  seems like only about 10% were good.

Caveat emptor.

Best regards, Jack

[noisette]

I bought those (seemingly?) a couple of years ago from goldmine and I think there were NSL32 rejects.
I think they were even cheaper? I got about 50 pieces and a lot were usable for compression, the rest for switching purposes without going bankrupt etc.

[Jarno]

Amazed that there is stil so much stock of non-ROHS compliant components...

Bought a few NSL32's on ebay a while back, also little money, so they might be the same, and they are ssssllllooowwww.
I am into Synth DIY, and for vactrol filters and compressors they definitely are too slow, for channel switching in amplifiers probably fine.

Recently bought dual Clairex vactrols on eBay, might have been a tip from around here, haven't used them in anything yet.
https://www.ebay.nl/itm/323436151039

More expensive though.