HELP! Adcom GFA-565 turn-on BUMP

[Numbdiver]

You guys were so great when I needed to fix the driver board cancer on my 565s, hopefully you can help me once again.

This problem has been there since the get-go, but I decided to ignore it. Since the amps have been repaired last winter, they work great, and have close to 0v DC offset.

That said, I can't turn them on OR off without a VERY large bump. In fact, I can't turn my other main amp off, or the servo off without a bump as well. So, I just leave them on. And never turn them off. Not the best scenario.

Here is a rundown of my system. Also, I've checked for DC on the preamp and servo box as well. I have Infinity IRS Gamma speakers which use a Adcom 565 on each speaker for the lows, and a Yamaha B-2x on the highs. A Yamaha C-2x is the Pre, and the pre has 2 sets of outputs, which are wired together internally. One set of pre-outs to the B-2x, one set to the Infinity Servo crossover. The Servo runs an RCA to each amp, and there is a feedback cable from each woofer accelerometer that runs back to the servo box. Everything is hooked up correctly (which is extremely important or you can get a run-away oscillation with the woofers).

So, I get a relatively small bump. I can live with that. But no matter what sequence of shut-down I do, and no matter whether the gain is turned all the way down on the servo box, I get 'bass pedal slamming into the bass drum at full force' bumps if I shut down any of the 3 amps or the servo box itself.

I've checked the current in-rush resistors, they are fine. It seems that there is just so much gain, and no way to turn the gain down, or disconnect the speakers when powering up or down.

Short of adding something like a Bryston speaker switch and using it as a speaker disconnect, any ideas?

I will borrow a Belles stereo amp in the next day or two, and replace the adcoms, just to take them completely out of the sytem for test purposes.

Any ideas at all, feel free to throw them my way. THANKS!!

Oh, all 3 power amps are on the same dedicated 20a circuit.

[Numbdiver]

I've been working this out over on AudioKarma. No solid answers yet, although it looks like the Adcoms are working fine.

I may have the gain switch on the back of the IRS servo box set too high (mid position). I didn't have the Bump issue with different amps in place, and the gain may just be too much for the Adcoms. I'm trying a different approach and will report back.

[Numbdiver]

Following up.

The amps and everything else were fine. I needed to turn the servo-gain down on the back of the IRS servo box (not to be confused with the LF gain control on the front of the unit). I'm now using the lowest (-12db) setting. No Bump issues.

Case Closed.