Put your old mpu board back in?

seen the same thing happen with bk2k. no fix. the only thing to do is find an original working board.

Now that I think about it it may be that DAC chip is the issue. Probably no longer available. If you take the DAC chip from your original board and put it in the rotten dog, it may clear up this problem

The Dac chip is u3, which is in the upper left-hand corner of the original board. It may not be socketed though. Might have to desolder it. But don’t damage that chip. They are just not available. Maybe the replacement that rotten dog is using is inferior to the original

This also might be relevent to your problem. My transporter speech sounded awful, loud, scratchy, could almost hear a heartbeat through the speakers. Is that what you are experiencing? The following link might be of use to you.

https://pinside.com/pinball/forum/topic/pinbot-sound-fix-w-rottendog-11a-mpu

This just seems to be a Rottendog board issue on some Sys 11 games. As my F-14 did the exact same thing, at low volumes it wasn't so bad but if you turn it up, the voices and certain sounds handled by the Rottendog are sooo much louder than the music and sound so distorted it was terrible. Not to mention, there's no bass and the sound is just flat. After repairing the original board it's like night and day, so much better sounds and voices are lower than the music and clear, as they should be. So now I have a very expensive backup if something happens to the original board again.

In summary of the other thread. The little daughter board on the mpu for the speech sounds has a resistor that is too low and sends too much power to the sound board. So when the two different sound sources are mixed, the mpu sounds are way over powered. There are quite a few fixes that have been come up with on the other thread.

Sounds like a thread is needed to cover all the fixes for the Rottendog MPU.