Music Man Amps

I've played MM amps since 19*cough*, anyway.... soo, where was I, oh - yes, I've only had one breakdown on stage thus far and it was in 1997 when a protection cap on one of the output tubes in my 112 65 combo died and took a fuse with it (but nothing else). Since then I have experienced the usual on stage oopsies, strings breaking, cables getting stepped on, pedal board gremlin suddenly flaring up, but my MM amps have been rock solid. Granted, as I've already bored you to tears with, my pet 112 combo has developed a power supply issue that I need to deal with, but I could just use my 130 head instead. I'd use it either as half stack 2x10 or the full 2x10+2x10 if I feel like it.

Last week Tuesday it was practice time before a show the following Saturday. The 130 head and the 2x10 cab went with me to rehearsal and after two songs I noticed that the distortion was on all the time. The controls were also up quite a bit higher than I'd normally play it at a quiet practice round Puzzled I plugged the guitar directly into the amp, bypassing the pedal board. Still distortion, not entirely unpleasant but the amp sounded weak and lifeless to boot. There was, however, no noise or hum involved - just a very noticeable distortion and lack of volume. The issue was the same on both channels too. The tubes, although not new, should be ok and they looked normal.

In my mind I thought it was either the phase splitter IC or possibly a bad driver transistor. Friday night, 24 hours before I had to be on stage, I got the amp taken apart and started digging. Signal coming out of the speaker output had the lower half of a sine wave cut off about 1/3 down. That would explain the distorted sound for sure, but not the underlying issue. The sound out of the master volume sweeper was clean, so the problem was most likely on the driver board. The signal coming out of the first IC stage was fine too - but at the output of the inverting stage I got only a faint constant buzz on the scope. 15 seconds and one $1.00 (Canadian) TL072 chip later I was back in business. The amp now sounds cleaner and louder than it has in months.

So, the morale of the story is that practice before a show is good - not only to polish the form but also to ensure your vintage gear is working. Would have been a real bummer if I hadn't caught that dead IC in time.

I think I just came up with a reason to buy another amp, we shall see if it passes a vote in that special committee where I have one vote and she has 20.

Cheers,
Lars Verholt