MM 90's & silent circuit

[ccollins46]

New here, new to MM but been playing 30+ years. Always kicked myself for letting my PRS Soapbar Custom with 3 P-90's go so after seeing Albert Lee live & up close and discovering the BFR Ghost in a Shell with 3 MM90's, I jumped. Hands down one of the best playing, sounding and feeling guitars I've ever played... it's #1. Ditched tele and strat.

BUT - the first one I got from the dealer (luckily they had 2), when plugged in made a God-awful racket so loud one couldn't play over it. Remove the battery and the noise was gone. Still, I wanted to receive the benefit of the so-called "Silent Circuit." I exchanged it for their other one in the shop. While it's not clearly defective like the former, after some play-in time, it buzzes like a mother - more than even with a fresh battery. Actually taking the battery out makes it sound better.

I'm not an electrical minded person - sure, I've re-wired (to diagrams) and swapped pickups in strats and teles and soldered speakers in cabs, but that's about it.

I'm hoping someone has some insight for me on making the Silent Circuit actually work. I haven't been "under the hood" yet mostly because I think it would be meaningless to me. Any tips or recommendations would be appreciated! Thanks, Chris

 

[beej]

First off ... congrats on an awesome guitar! (Let's see some pics, hint, hint ...)

The Silent Circuit is a buffered dummy coil that adds some out-of-phase noise to the signal. It's not that complicated- so either it's set up / wired up wrong, or it's broken (and replacement isn't too difficult). The good news is that it's under warranty, so you'll be taken care of.

First off- do you get the noise in all 5 switch positions?

Where it adds noise- try adjusting the potentiometer on the Silent Circuit. It should reduce / increase the hum as you dial it out. If it's truly adding hum, there's a chance it's wired up incorrectly (though that seems unlikely). You usually find the sweet spot where it reduces the noise as much as possible. (This is best done with the guitar in playing position, away from any external noise sources.)

If this doesn't help- reach out to the store you bought it from and let them know, or since you're in the US you can contact Music Man directly and get their advice.

Let us know how you make out. (After posting pics, of course.)

 

[ccollins46]

I haven't looked under the hood yet to adjust the silent circuit yet as I'll be changing strings next week for a gig and will do so then. But interestingly, I plugged into a different amp in a different room - and it's quiet. Silent circuit not engaged b/c I removed the battery previously. Seems maybe some Class A amps hum more than others?

 

[beej]

For reference, with the battery pulled the SC is out of the circuit (the "virtual ground" it provides is the same as ground).

If you put it back in, with the new amp what happens?

Some amps definitely make more noise than others. But it's likely proximity to a noise source (something external or the power transformer of the amp) that makes the biggest difference.