Not sure if it is the same problem but someone had bad sound with a rottendog MPU in an F14 a few days ago.

https://pinside.com/pinball/forum/topic/f-14-sound-issue-wrottendog-mpu#post-3163476

Rottendog may have a bad batch of parts and their standard lack of quality control has not caught them.

I just installed a rotten dog MTU in my transporter. I too am having the same issue with the voices sounding scratchy and unclear. The noise issue goes away when I unplug the audio cable from that daughter board. I too will be emailing rotten dog to see if there is a remedy.

I have a system 11b Mpu 100% working if someone is in need. I need to raise funds for a HD I'm working on

Bump. . .anyone else have this problem? It seems related to that auxiliary sound section that plugs into the main board. No response from RD either.

I have emailed RD asking question about a system 11 MPU board. No answer over a month.

listen, that board will also not work in elvira or fire. certain sounds (speech) are very distorted.
i tried more than one of those new mpu, also spoke top him on the phone, sent both boards to him.
they just dont work correct in some games.
the stock boards worked fine in the same exact machines.

That sucks. . .the Kohout system 11 board works flawlessly and of course they quit making it. I am floored at how bad the game sounds. . .I guess don't connect the sound from Rottendog's MPU to the sound board. What a pisser.

"listen, that board will also not work in elvira or fire. certain sounds (speech) are very distorted. . . .they just dont work correct in some games." Add Transporter the Rescue and Big Guns to that list. Although I suspect that if I put that damn board in my other system 11's it will sound like crap too.

it works ok in CYCLONE that i have tried.

I called Jerod (http://rottendog.us/contact%20us.html) when I was having this exact problem on my Taxi. He asked me to send it in, but the game was going on location the next day so I just rolled with it.

Bump. I'm having this exact problem with an Elvira. Has anyone found a resolution?

I had this issue on my Pin-Bot. I added a pot on the red wire of the input harness from the daughter board to the sound board and it took care of the loudness issues from the sounds from the MPU daughter board. But my helicopter noise is still there. Not as loud, but it's still there. Rotten Dog sent me a new chip for the board (not sure which one), and when it didn't work they basically shrugged and said sorry. I bought the game with the MPU already in there, so i didn't raise too much of a stink with them since i wasn't the original owner of the board, but with all the same issues people are having, i was hoping for more of a roll of the dice then a shoulder shrug.