Transistor relay switch from line level AC signal - I Need Help!!

barrelwaves said:

As i said, the new design is tried and tested and working much much better. and really is the simple way of doing it, opamps tend to act a little different in real situations and funny enough not very well for mine. The final design of the opamp version was moderated and accepted as the "way to do it", with your schematics and all the others incorporated correctly. But in this case i have found the simple full wave rectifier to work much better. Because it works you see.

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There was no working opamp design posted by you in this thread?, and no posts suggesting your posted circuits were viable?. Personally I don't use simulators, but an opamp design like you should have used is so simple, and so obvious in it's design, that there's no need to simulate anyway.

The bridge rectifier 'design' is basically just the opamp circuit without the opamp amplifier on the front, but instead of one diode drop you lose two of them, plus the voltage require to switch the darlington driver arrangement.

Have you tried it with a single diode rather than the bridge?, to reduce voltage drop you could use germanium diodes rather than silicon.

Could anyone tell me what the peak or RMS voltage level is for line level running at +4dBu Please?

Paul,

+4dBu is 1.228V(rms)

Hi Sam!

Yer nice one i measured it out of my sound card and found the same, which is very very handy because the circuit will work as it is now with 1.2v input required! Lovely

See you in the grime wednesday
(If this is the same sam Jelfs?!)

there is only one Sam Jelfs

yeah, shall see you in the labs on Wednesday, hopefully we'll both be having a bit more luck by then!