A year with the MT15

Oscar

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Nov 26, 2021
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39
Impressions of a year with the MT15.

Reliability
The first one I got had a faulty standby switch and lots of hum in the FX loop. Returned it and received a second one which so far has been reliable.

The FX loop hum issue
I’ve found that (like a single coil pickup) the potential for loop hum is just there with this amp, but I’ve always managed to make it go away. Just throwing a pedal on top of the MT15 or directly besides it and hooking it up means hum. In contrast, good cables with straight jacks moving horizontally away from the amp in a straight line seem to work best, i.e. by putting my pedals on a table or a beer crate about 2 feet behind the amp. When using patch cables with angled jacks or if the pedal has to sit on top of the amp or besides it, then to find the sweet spot I move around the pedal and both cables with the amp switched on. Carefully positioning the cables relative to the amp and its mains cord really makes a big difference and if necessary I use some tape or tie-wraps to secure them. At first it was a hassle but by now I can do it in a minute. It doesn’t bother me anymore, because I can quickly make the hum go away.

Clean sound and pedal platform
The amp’s clean sound was its main selling point for me. Sweet, chimey, articulate and punchy. The controls are really effective to bring out the best in a guitar and most of the time putting them all at noon will work fine. With hollow body guitars and archtops I may need to fiddle around a bit, but with most solid body instruments noon will do. The channel’s bass response changes when switching the amp to 7 Watt mode; it becomes less thumpy.
The clean-boost function is something that I rarely use. Haven’t been able to find a good use for it yet.
Love the way the amp takes pedals through the clean channel!

Dirty sound
At bedroom volumes the bass respons of the drive channel is flimsy compared to the robust lows of the clean channel, so for dirt I really prefer the 15 Watt setting. Turning up the master increases the bass response of the drive channel but also rearranges my internal organs so I guess it’s the age-old question of finding a compromise between tone and volume (but that’s what I grew up on). I prefer to use my favorite drive pedal into the clean channel, but when judged on its own the MT15’s drive channel is excellent. It cuts through without being harsh, responds well to dynamics and the guitar’s volume control and sounds great with a variety of guitars. Powerful, articulate, transparent and creamy is how I’d put it. Of course it’s a modern high-gain channel by design and should not be compared to (say) a plexi or a JCM800. I use an Ernie Ball volume pedal that doubles as a boost to navigate the gain and it’s a trip.

Volume taper
The clean channel can be easily dialed in at any volume. As has been widely noted, on the dirty channel the master is jumpy and the amp might melt your face if you’re not careful. Everyone who grew up on Marshalls will be used to this. The more gainy a channel is, the harder it becomes to make the master turn up gradually. I saw a vid where Tremonti explained that in fact this is the final point that’s holding up the MT100. Anyway, I can get the amp to sound good at the levels I require. A delicate touch will go a long way.

7 Watt / 15 Watt
The 7 Watt setting has its own mojo going and changes much more than just volume. I use it a lot with jazz boxes to clean up some low-end boominess. Very pleased that the amp has this option.

The bang and the buck
I don’t hear the MT15’s price point. What I hear is a really nice amp, regardless of price point. I can live with the master volume taper and I can get the loop to behave, although with a bit of fiddling around. Love what the clean channel does to my favorite drive pedal. Love the versatility and 7W/15W option. I was bummed that the first one I got was faulty but I really like the one I have now. I’d buy it again.
 
Nice recap! Regarding the FX lop noise, was it always present or just when using certain pedals? How "bad" was it? Mine (bought second hand from a friend) worked like a charm, except for the noisy FX loop when using a Mr.Black Supermoon reverb - but I later found out that it is also the effect pedal that was noisy, so I have to check that again, but the noise was much more intense when going trough the FX loop compared to the front of the amp. It started to make a weird noise two weeks ago, but I hope it is maybe just a damaged 15/7W switch, could have damaged it one time I took the amp to a jam and could have put it badly in the trunk of my car, will see soon about that. Otherwise love the amp, love the sound and it is a small tank. I pimped it a bit, replaced the cheap/ugly knobs ;) and experimented with different tubes, now I have a 5751 in the PI (V6) position and a JJ ECC83 in the FX loop.

Have you tried different tubes maybe?
 
Regarding the FX lop noise, was it always present or just when using certain pedals? How "bad" was it? … Have you tried different tubes maybe?
Almost all of the hum comes from the cables to/from the pedal. Not from the pedal itself. When the cables are in certain positions relative to the mains lead, the transformers etc, then there’s hum. Now that I know where (and where not) to position those cables, problem solved.
I’ve not had reason to try different tubes yet.
 
Almost all of the hum comes from the cables to/from the pedal. Not from the pedal itself. When the cables are in certain positions relative to the mains lead, the transformers etc, then there’s hum. Now that I know where (and where not) to position those cables, problem solved.
I’ve not had reason to try different tubes yet.

Interesting stuff Oscar. Would you be so kind and elaborate a bit in regard to the positioning of the cables, straight/angled jacks, do cable brands matter, how long are your cables, does speaker proximity matter, etc.? It is worth trying out, will be putting my gear in the middle of the room and doing everything by the book ... let's see, if that solves my issues I'm buying dinner when you come to Ljubljana.

I tried some of the advice as to not cross mains and guitar cables (also power and signal cables on the pedalboard), using straight jack out/in the amp, using high quality cables and jacks I put together and tested myself, using an isolated power supply, but I did not find that to make a noticeable difference in my case ... maybe I did something else wrong or overlooked something.

Are you maybe using any other "extra" gear? Are you using 4 cable method, any kind of noise suppression pedal? What does your signal chain look like?

Regarding the tubes, I mainly wanted to test what kinds of sound I can get out of the small beast, but it also came handy as I found out one of the JJ was a bit sketchy and was then able to replace it. As a side note, I found out the hard way that it is very important to have a reliable "tube source", as there are different views and sometimes misconceptions regarding what that "special" NOS (usually more expensive) tube does to the sound compared to a cheaper one.

About the bang for the buck, I think this is a real good deal (if everything works and if you are into the sound it makes ... and I am).

Cheers
 
Hi! In my original post above I described what works best for me with the cables. That’s all the info I have. I don’t use any extra gear. Just one reverb pedal in the loop, that’s it. I’ve heard stories that some owners report their MT15 to be quiet while others just can’t get rid of the hum. From a design perspective there are two main challenges with the MT15: 1) price point; 2) squeezing it into lunchbox size. I guess PRS did not compromise with sound, but they did with the loop.

Finding really good tubes is a hassle, but to my ears it’s worth it.
 
Noting, Oscar is not the first to find orientation and location of the pedals and loop cables to be important in fighting loop noise.
 
How do y'all feel about the lower-gain sounds of the red channel? I.e. with gain at 9 o'clock?

I like those, especially with the neck pickup and a volume pedal with boost function. From clean to scream and really shows the tone of your guitar.
 
Nice recap! Regarding the FX lop noise, was it always present or just when using certain pedals? How "bad" was it? Mine (bought second hand from a friend) worked like a charm, except for the noisy FX loop when using a Mr.Black Supermoon reverb - but I later found out that it is also the effect pedal that was noisy, so I have to check that again, but the noise was much more intense when going trough the FX loop compared to the front of the amp. It started to make a weird noise two weeks ago, but I hope it is maybe just a damaged 15/7W switch, could have damaged it one time I took the amp to a jam and could have put it badly in the trunk of my car, will see soon about that. Otherwise love the amp, love the sound and it is a small tank. I pimped it a bit, replaced the cheap/ugly knobs ;) and experimented with different tubes, now I have a 5751 in the PI (V6) position and a JJ ECC83 in the FX loop.

Have you tried different tubes maybe?

Just to clarify with an update ... as I am learning along the way and in light of new events and discoveries :) ... looks like I found the culprit of the FX loop issue and it could be bad grounding of the FX loop pcb or a bad jack socket, also I must say I could have waited a bit longer before sending the Supermoon pedal back, although I felt like it was quite noisy even plugged in front of the amp - weird, because none of the YT reviews had any hiss/noise and nobody mentioned it.
 
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