Automatic Audio Standby Circuit

standby circuit

I am designing a subwoofer and would like to include an automatic standby circuit to automatically switch it on/off depending on whether a signal is present or not for a certain period of time. I know that this is easily done with a microcontroller, but I want to do it the harder and more satisfying analog way.

I know this must circuit exist, but amazingly I have only come across one circuit online at h**p://home.uni-one.nl/hans/ which is based on a 1996 Elektuur article. I don't completely understand the circuit operation (sorry, my analog is rusty) although I know it’s a comparator driving buffer/amplifier. I am unable to get a copy of the original circuit on which it was based. My quick Multisim simulation did not prove anything, although I will run it again and look at the circuit more careful.

I would appreciate any input. Thanks.

I can't see the schematic on that web page (it seems to be broken), but here is another auto-power on circuit. It has a pretty thorough description of how it works as well as schematics.

**broken link removed**

I hope it is what you are after.

Thanks for the reply. I just found this circuit too. I realized that the circuit is nothing more than voice-activated switch (VOX) and did search and this came up. Subtle word changes do make a big difference in Web search results.