Mesa M-Pulse 600 BIAS

[PJay1]

Does anyone here know the BIAS procedure for a Mesa Boogie M-Pulse 600 power block? Thanks.

[Enzo]

I'll bet Mesa does, they are there Mon-Thurs. Call them.

[DivAud]

First you need to turn the bias down, usually counter clockwise turns the bias down. A safe way to find out the direction is put the amp on a load lamp and turn it in the direction that makes the lamp the dimmest.

Next, put the amp on a dummy load, turn the load lamp off, feed a 10K signal into it and adjust until the crossover distortion just goes away. Make sure you do not over bias this amp, it will over heat, run away, and blow up if it is over biased.

Next check the DC voltages on the .22 ohm resistors in the output section. This should be quite small, my guess would be 4 MV or less.

If you do not understand what I have said here, you probably have no business in this amp, Take it to your local repair shop and have it biased, this is not like a tube amp that needs biased when the output tubes are changed. This should only need biased if the power amp is rebuilt, or checked if the power amp is running too hot....!!!!!

If the amp is running fine, I would leave it alone......

[Steve Conner]

This is a good point. Why do you think you need to bias it? The only valid reason would be if you've replaced the output transistors. And since this is a MOSFET amp, you're opening a can of worms.