5.1 amplifier speaker protection

[macplauder]

Hi everybody,

I just finished my 5.1 PC amplifier on the breadboard and it is working great so far. If anybody is interested I can post a schematic. Its basically the Earle Eaton headphone amplifier with higher supply rails (+/-21V) and the bias resistors replaced with current sources, it should give around 18W per channel.

The amplifier powers fairly expensive speakers (or my Beyer dynamic headphones) so speaker protection is a must. So far I'm using 100uF NP output capacitors to protect the speakers but these give a corner frequency of 198Hz and already gobble up plenty of board space. Bigger capacitors are no option because the whole amplifier has to fit in a fairly small monitor stand box.

I spent hours searching for a simple and small DC detection circuit but to no avail so far. Since 6 channels need to be protected, the board size and complexity piles up with the rectifier diodes, filter caps and transistors needed. What is needed is a simple circuit either using a special IC or making use of highly integrated circuits such as SMD quad op-amps. The special IC's I found on ebay are for stereo-use only and still require a fair amount of additional components. Maybe it is possible to use a PIC controller to sample the outputs with its integrated A/D converters, then shift & sum up the values to see if any DC is present?

Any suggestions are greatly appreciated.

Best regards,

macplauder

[ingenieus]

Check this out

Project 111 - PIC Based Speaker Protection

[AndrewT]

3 dpst relays (double pole single throw) can isolate all 6 outputs.
A 5.1 amp system is probably working from low voltage rails with lowish capacitance in the Power supply. The relays may survive a serious fault interuption.

One detector system to activate all 3 relays simultaneously, with a big RED flashing LED to tell you it is in protection mode, should not use too much space.
I think pic and some of the discrete detectors can run with 6ch inputs .