optocoupler to replace mic for tube amp

[tedmich]

Hi all,

I have a circuit which varies LED intensity with sound level and am interested in replacing the 1.5k electret condenser mic with an optocoupler to allow me to drive the circuit off the tube signal.

Is there an FET optocoupler which could replace the mic in this circuit:
http://lh4.ggpht.com/_WbJ1JcTROqQ/St...g/s800/mic.jpg

and respond to the HV signal from the preamp?

I'll share the circuit when I get it to work

[Enzo]

Um, I guess I donl;t get the question. Optocoupler as a mic?

In general, your mic circuit simply produces a signal at the OUT. Whatever receives that signal has no idea whether it came from an electret mic capsule, a dynamic mic capsule, or a CD player.

SO whatever is offscreen to the right is expecting some signal which it will then display the average level of - a VU meter circuit of some sort.

You could grab a signal from anywhere in a circuit, use a cap to block any unwanted DC, and a couple resistors wired as voltage divider - or a pot wired as a volume control - to bring the level down to what you might need for the offscreen bits.

really, all you need is an FX send sort of thing.

[Steve Conner]

My head hurts. What are you trying to do? Optocouplers already have a LED inside that needs driven. So you'll need a circuit that varies a LED intensity with sound level, to drive your circuit that varies a LED intensity with sound level.

Anyway, the H11F1 JFET optocoupler will probably do whatever it is you're trying to do, but more expensively than just coupling the signal into the circuit with a couple of resistors and capacitors.