PRS MT-15 Lead Channel Issues

[phoztek]

Hi all,


I'm fairly new to amp tubes and i've acquired a PRS MT-15 last week, but for some reason I think it has an issue and wanted to have you guy's opinion on this.
The clean channel works like a charm, I can get a pretty good sound out from it, but the lead channel is a whole different story. I've heard almost every video's out there, and I can't get anywhere near the tones I hear.
I know that most youtube and similar videos are post processed sounds but when listening to those videos where you have the mics from a camera or phone or any other capture devices not digitally processed, mine just doesn't sound alike.

I have the MT-15 connected to a 2x12 Harley Benton cab loaded with Celestion V30s, I have several types of guitars / pickups, some with more solid woods and others semi hollow, good cables, no ground issues.

The First thing I noticed, the lead channel doesn't get that saturation and seems that gain only adds muddiness to the sound, it doesn't feel tight at all. It feels like it's more like crunch than high gain distortion.
The bass knob, after 12 o'clock is non-existing, it's like it reaches its max at that position.
The overall lead sound has so much bass that In order to make it more or less ok, I have to reduce the bass to 9 o'clock.
I've tried the cab in different positions, heights and this doesn't seem to be the issue, it's still there. I've also tried two other cabs and got the same exact result.

I'm guessing that during the shipping, a valve might have got damaged somehow? Is this possible? To still have sound coming out but have a defective valve?
What do you guys suggest? Also would appreciate suggestions on what valves to replace and which ones are the better in your opinion ( i've heard people changing the 6L6's with EL34's and many others.

Thanks in advance!

 

[Deleted member 5962]

Did you buy it new, or used?

 

[phoztek]

Did you buy it new, or used?

Used 2nd hand

 

[Deleted member 5962]

Check the preamp tubes used in the gain channel first. Do you have "known good" replacement tubes you can roll in?

 

[phoztek]

Check the preamp tubes used in the gain channel first. Do you have "known good" replacement tubes you can roll in?

I pretty tech-savvy, but I don't have any replacements yet. Today I have band rehearsal, and after I'll just reset all the tubes and check it again. From what I read, gain comes from V1 and V2 ? Should I also consider the 6L6 replacement? If I can't get it working properly, I mean!

 

[Deleted member 5962]

If the clean channel sound right, I'd focus only on the gain channel pre-amp tubes first. Look at the tube chart for the amp and focus on those. Even one good new 12ax7 would give you one you could roll through those positions to see if one is bad.

 

[Dougu]

Hi all,


I'm fairly new to amp tubes and i've acquired a PRS MT-15 last week, but for some reason I think it has an issue and wanted to have you guy's opinion on this.
The clean channel works like a charm, I can get a pretty good sound out from it, but the lead channel is a whole different story. I've heard almost every video's out there, and I can't get anywhere near the tones I hear.
I know that most youtube and similar videos are post processed sounds but when listening to those videos where you have the mics from a camera or phone or any other capture devices not digitally processed, mine just doesn't sound alike.

I have the MT-15 connected to a 2x12 Harley Benton cab loaded with Celestion V30s, I have several types of guitars / pickups, some with more solid woods and others semi hollow, good cables, no ground issues.

The First thing I noticed, the lead channel doesn't get that saturation and seems that gain only adds muddiness to the sound, it doesn't feel tight at all. It feels like it's more like crunch than high gain distortion.
The bass knob, after 12 o'clock is non-existing, it's like it reaches its max at that position.
The overall lead sound has so much bass that In order to make it more or less ok, I have to reduce the bass to 9 o'clock.
I've tried the cab in different positions, heights and this doesn't seem to be the issue, it's still there. I've also tried two other cabs and got the same exact result.

I'm guessing that during the shipping, a valve might have got damaged somehow? Is this possible? To still have sound coming out but have a defective valve?
What do you guys suggest? Also would appreciate suggestions on what valves to replace and which ones are the better in your opinion ( i've heard people changing the 6L6's with EL34's and many others.

Thanks in advance!

Hello everyone, newbie here.... Owned my mt 15 well over a year and as a hopeless tone chaser i was immediately overjoyed when i first heard it..no opp.amps or jfet trickery's! Just pure tube fire!! Warts and all and i rolled tubes so much i can tell u with 80%certainty either v2 and IS the 2nd preamp from bottom right( try switching with the lonely phase inverter #6 preamp and see if it improves. If not it's likely the power tubes and would require biasing when changed..... I hope u have the issue resolved and if this was a help , of course set out to aquire a new phase inverter tube as it will only improve and the amp is capable of much better if your v2 was that defective.

 

[Goran Lorencin]

As said before, it is good to buy a few preamp tubes (12ax7, 12at7, 5751 - depending on the sound you are going for), and a pair of power tubes (6L6GC or 5881 for example) and have them on stock for this kind of situations or for dialling in "the sound". Roll the tubes and see what happens. I would stick with "original" replacement tubes for now, do not put EL34's in for now, stick with what the amp was designed for. Next thing to do is to get "educated" with going trough Rob Robinette's page about tube amps and then get back to us with the results. It took me quite a while to diagnose my MT15 issue, in the end I replaced the FX loop jacks, resoldered a few spots on the inside and changed a few tubes. Now it has a kickass sound without any issues ... as far as I know.
Regarding the EQ, it is very subtle, do not expect big changes. I also bought a HB 2x12 cab and swapped one V30 for a Jensen Electric Lightning and made a custom back.
Biasing the power tubes is very simple, all you need is a multimeter and a small screwdriver. This is basically a very straight forward tube amp. Maybe take the bottom off and look for any suspicious signs. But be careful and take safety precautions to not get in the way of electricity flowing trough the pcb if you will be poking around.
Hope you get it to sound as it should.

 

[Goran Lorencin]

Hi all,


I'm fairly new to amp tubes and i've acquired a PRS MT-15 last week, but for some reason I think it has an issue and wanted to have you guy's opinion on this.
The clean channel works like a charm, I can get a pretty good sound out from it, but the lead channel is a whole different story. I've heard almost every video's out there, and I can't get anywhere near the tones I hear.
I know that most youtube and similar videos are post processed sounds but when listening to those videos where you have the mics from a camera or phone or any other capture devices not digitally processed, mine just doesn't sound alike.

I have the MT-15 connected to a 2x12 Harley Benton cab loaded with Celestion V30s, I have several types of guitars / pickups, some with more solid woods and others semi hollow, good cables, no ground issues.

The First thing I noticed, the lead channel doesn't get that saturation and seems that gain only adds muddiness to the sound, it doesn't feel tight at all. It feels like it's more like crunch than high gain distortion.
The bass knob, after 12 o'clock is non-existing, it's like it reaches its max at that position.
The overall lead sound has so much bass that In order to make it more or less ok, I have to reduce the bass to 9 o'clock.
I've tried the cab in different positions, heights and this doesn't seem to be the issue, it's still there. I've also tried two other cabs and got the same exact result.

I'm guessing that during the shipping, a valve might have got damaged somehow? Is this possible? To still have sound coming out but have a defective valve?
What do you guys suggest? Also would appreciate suggestions on what valves to replace and which ones are the better in your opinion ( i've heard people changing the 6L6's with EL34's and many others.

Thanks in advance!

One other thing you could do is to make a video/audio recording and let us hear what is going on. Maybe it's all ok. The gain channel and EQ do behave similar to what you described. Does the master volume also go from 0 to quite loud in the first few degrees of turning it?

 

[Sybo]

How do you know what version you have?

 

[Goran Lorencin]

Inside on the pcb are the numbers. You have to unscrew the bottom plate.

 

[Sybo]

Thank you!