"M" means it has the tighter gain/low end mod installed from the factory, and the upgraded tourmaster Output transformer.
I hope you got a "good" one. This seems to be the place that pops up first in google search when people have a problem with one of the Tourmaster Amps, so by default, ends up being the dumping ground for all the sneers towards this amp series.
I digress! What a SUPER versatile amp, not very highly regarded as they're made in China and there were some notorious issues with the early ones, but man, they do have some killer tone in them. And hey, who can argue with Micheal Wagener touting that he has/had one in his own personal recording studio. I also think the amp design/color and grill are super nice looking and classy.
Takes pedals well, sounds great with just about any of the guitars (tele/superstrats/les pauls/sg) i put through it.
All 4 channels are laid out nicely and each at its most aggressive kind of transitions into the next channel>>>
Another watermark of a nice amp tone IMHO, is something you WANT to play, YMMV and issues aside, to which again, I hope yours have none. Definitely a cool amp to play and get inspired with, and each channel kicks a lot of ass in it's own right.
I've found the amp's master volume is key to good tone and consistent volume matching across the 4 channels. I like that amp master volume up around 1/2 o clock on the dail IIRC as well. The resonance adds a TON of low end, and the presence does it's job well in the fizz deparment, but can get a bit harsh at lower volumes. Seems less effective (sort of like a peavey 5150) until =you hit around 3pm on the dial, except at louder volumes and power grid settings, the presence seems to work a bit more around the dial, which makes sense. These global controls (the power grid, master volume and res/pres) REALLY interplay well with the rest of the amp.
Worth mentioning right off the bat is the effects loop. Switchable parallel/series is nice. A nice trick is to put a patch cable between in/out and set your send and input levels as a built in footswitchable boost over your channel your on
The loop interplayed well with rack and pedal gear I put through it, but I liked it most as a built in tube boost, even if it's 'not really' a tube boost, it works great for a transparent volume boost!
The contour knobs and vintage/modern switches have pretty wide range of effect on each channel's tone, making each channel even more versatile. Definitely a variable multiplier in the world of tones you can dial in on each channel, and worth checking out extensively, because one setting on contour could vary from the slightest adjustment at stage volume, something you'll learn I'd guess the longer you play with the amp and your different guitar tastes.
-Clean 1 is a killer clean channel and with the power grid, you can get some edge of breakup tones, etc. Really fun channel and i'm eager to hear some pedals through it that I didn't have when I was using this amp heavily (Bogner red, Friedman BE-OD, Mesa 5 band). Many a tone could be had with just those 3 pedals, so the options are exciting combines with this amp! Beautiful sounding cleans and the reverb in these is matched/voiced phenomenally to the channels! Contour engaged around full blast
and the modern setting engaged, you can get a fairly convincing acoustic type sound. I say "type" because, obviously....but it does it nicely and sounds great!
-Vintage 2 is a plexi type clean and can cop the Led Zeppelin "Heartbreaker" tone with ease. You could play a whole gig on this channel alone with a boost and a dirt and get away with a LOT of styles. This channel also cleans up well. The contour and vintage/modern switch in this channel lends to a wide array of tones again and you're bound to find a tone you like in this channel!!
-Overdrive 1 is where it's at in this amp, IMHO if i had to choose. Again, as with the previous two channels, one can expect to cover a lot of ground with just this channel and spend a lot of time here jamming! It's well worth tweaking and messing with and getting to know this channel and it's parameters and capabilities, as there are many more and suprisingly, this channel is dead quiet at LOUD window shaking volumes.
-Overdrive 2 is a heavily compressed, scooped, but not too scooped sound. The brootz are there whether you like your gain just on the edge of saturation or full saturation and the gain knob should be experimented with pending pickups (as in other guitars) because some sound like mud with heavy gain
My experience w this amp:
I was really excited to have it. I traded a Mesa Heartbreaker for it that I hated, but never had an issue. When I heard and played the TM it seemed like a good fit, but I had no idea there were so many problems with them. I was sold on the tones of each channel immediately, and the versatility really speaks to me with any piece of gear, so there's also that.
I've had a number of issues with my tourmaster though, unfortunately. While I do believe I was one of the last Egnater customers to receive the gratis (i did pay shipping?) output tranny replacement, and thorougly thankful as such, it was a chore to obtain for some odd reason. I installed it myself, and it was fairly easy and the customer service agent actually helped me a ton!
Soon after the output trans replacement though, the reverb quit working. It was determined to be the reverb trans that malfunctioned through some troubleshooting here through PM with Bruce Egnater. I bought and replaced that and it sounded great for about another 20 hours of jamming, and then went out again (reverb). Super frustrating.
Recently, this past winter, I was using it and channel 4 crapped out, and i have since to crack it open (i have the combo) and mess with the tube, as that is the problem i'm hoping for and first logical place to start (*fingers crossed). I just haven't had the time to get the back open and mess around with that channel's tube, so I can't really say if this malfunction is a standard tube issue, which, let's face it, as a guitar player, be prepared to deal with tube issues at some point or another.
I didn't gig it, but it held it's own in a band setting driving a krank cab with texas heat speakers in it during rehearsals (cab was borrowed)
Super loud, and can also be tamed down with the power grid settings, which i REALLY like and find to be useful. 10 watts gets these amps roaring with the amp master cracked open at that sweet spot i mentioned earlier, and channel volumes up around noon.
You can also set your power tube bias across the 4 output tubes, which is a nice, overlooked feature on many other amps.
No issue with the tones, and I actually got my feet off the ground modding/repairing (kind of fell into it actually, or progressed out of neccessity!), just the reliability, again, fingers crossed you don't deal with any of that.
Have fun with it, obviously i'm a stubborn goat and won't give up on my TM anytime soon lol.
Hope this helps and good luck w yours!!! If you gig with it, as with any gig situation, just have a backup w you