Tube Layout Chart for MT15?

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I put a JJ EC81(12AT7) in V3 and gave me more useable gain.....not as harsh.
I tried a Tung Sol 12AX7 in V1 and got a more Marshall-like sound.
I currently have a Ruby 12AX7AC5 HG+ In V1 and love it.....sound is between a Marshall and a Diezel VH4....to me anyway.....
 
I tried a Mesa AT7 in the Pi slot, also tried it in V2 and V3. It does drop the gain a little bit in the V1&2 but I'm a high gain guy so went back to the 12ax7's. The feel of the gain response in the Pi slot made it feel "flatter" in response if that's any help. For lower gain users I think this is great for sure.

Also dropped $40 on a Genalex premium 12ax7 and...Just a recommendation get something half price lol. I compared with a Mesa 12ax7 and the tone difference in negligible at best
 
Also dropped $40 on a Genalex premium 12ax7 and...Just a recommendation get something half price lol. I compared with a Mesa 12ax7 and the tone difference in negligible at best
That is a very highly rated tube for new stuff. What slot did you put it in?
 
I ended up removing it and saving it. That being said, I got this amp for the gain and also play a baritone in Drop G# so my opinions don't always translate especially when the thread was more about seeing a gain reduction. In addition the amp is fairly new so the stock tubes are also still quite new. Next will be an EL34 swap, I had them replacing the 6L6's in my Triple Rectifier and loved them.
 
First time looking at swapping tubes here. Call me dense, but V1(input) is located next to the input jack like most amps, right? The chart appears opposite. Standing at the back of the amp with power tubes closest to you, it shows the loop tube to the left of the power tubes rather than to the right of them(as it is on the actual amp).
 
First time looking at swapping tubes here. Call me dense, but V1(input) is located next to the input jack like most amps, right? The chart appears opposite. Standing at the back of the amp with power tubes closest to you, it shows the loop tube to the left of the power tubes rather than to the right of them(as it is on the actual amp).
Yes V1 is in front of the input, then V3 (2nd stage) and V4 (3rd stage). Then V2 (clean) and V5 (loop). The single that sits toward the power tubes is V6 (Phase Inverter)
 
Hi all, I just stumbled on this topic while researching recording amps. The MT15 sounds about perfect except for the aggressive metal character (I know, that's saying love the car except for the engine). I've done this kind of thing before years ago with a Mesa Studio preamp, and a 12AU7 (you read that right) smoothed it out to a gorgeous blues recording amp. So, my question is, since V2 and V3 are the Lead "gain" tubes, does V2 correspond to the Gain knob and V3 to the Lead Master knob? Or vice-versa? In that case, wouldn't it be better to swap out V2 instead of V3? But people here seem to find the V3 swap to provide a better gain sweep. Perhaps best to change both, eh?
 
The effects driver is the last tube in the line to the left looking at the front of the chassis or V5 not V6. Thought the same thing as the chart here is saying but it's wrong. Have both a MT 15 and a Archon the Tube functions are the same in both but the Archon lists the PI as V5 and the Effects drive as V6 go figure from the charts that PRS gives you.
From PRS
https://www.prsguitars.com/documents/mt15_tube_chart.jpg
 
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My gosh and fudge ... it looks like I had it all wrong, was thinking that the V1 was the first from the left when looking at the amp from the front. And as it turns out it is the first from the right, nearest the input jack ... is that correct?
 
Love what you all are sharing in this thread. I'm a tube rolling newb so this is pretty encouraging. I absolutely love the clean channel with the gain boost knob pulled but have been wishing to tame the lead channel. On other forums I've just been met with "take the MT15 for what it is or get another amp."

What I mean by "tame" is that I don't like not having more fine adjustment of the lead gain - to my ear, with 12AX7s it's already super compressed heavy crunch at 8:00 - 9:00 on the dial. I guess this is what some of you are referring to as "taper"?

I read Tube Depot's write up on the 5751 and they echo Andy474x. I'm going to try both the 12AY7 and 5751 in v2 and v3 (each slot individually and together) and share what I hear.
 
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The effects driver is the last tube in the line to the left looking at the front of the chassis or V5 not V6. Thought the same thing as the chart here is saying but it's wrong. Have both a MT 15 and a Archon the Tube functions are the same in both but the Archon lists the PI as V5 and the Effects drive as V6 go figure from the charts that PRS gives you.
From PRS
https://www.prsguitars.com/documents/mt15_tube_chart.jpg
So essentially the chart is as if you were looking at the amp from underneath. Brilliant. I have to say I suspected that looking at the position of the input jack and various knobs...
 
Love what you all are sharing in this thread. I'm a tube rolling newb so this is pretty encouraging. I absolutely love the clean channel with the gain boost knob pulled but have been wishing to tame the lead channel. On other forums I've just been met with "take the MT15 for what it is or get another amp."

What I mean by "tame" is that I don't like not having more fine adjustment of the lead gain - to my ear, with 12AX7s it's already super compressed heavy crunch at 8:00 - 9:00 on the dial. I guess this is what some of you are referring to as "taper"?

I read Tube Depot's write up on the 5751 and they echo Andy474x. I'm going to try both the 12AY7 and 5751 in v2 and v3 (each slot individually and together) and share what I hear.
We need a strict "no bumping threads started by deleted user" policy here. This guy starts a thread, bails, and now gets a residual check 4 years later. It's just not fair! :rolleyes:

:p:p:p

On a serious note, I always recommend a 5751 when you want a lower gain replacement for the 12ax7. While you can use the others, the 5751 is the only one that has the same characteristics electrically, but less gain. IF you want to tame the beast a bit, I think the consensus of those who tried it, was to replace V3, and I'd suggest that you use a 5751 first. .
 
Love what you all are sharing in this thread. I'm a tube rolling newb so this is pretty encouraging. I absolutely love the clean channel with the gain boost knob pulled but have been wishing to tame the lead channel. On other forums I've just been met with "take the MT15 for what it is or get another amp."

What I mean by "tame" is that I don't like not having more fine adjustment of the lead gain - to my ear, with 12AX7s it's already super compressed heavy crunch at 8:00 - 9:00 on the dial. I guess this is what some of you are referring to as "taper"?

I read Tube Depot's write up on the 5751 and they echo Andy474x. I'm going to try both the 12AY7 and 5751 in v2 and v3 (each slot individually and together) and share what I hear.
Hey man, good to hear there are others doing their own thing with the MT15. I'll tell the abbreviation of many of my posts, first of I think that the BIG thing many tube amps offer (compared to solid state) is the option of having many amps in one amp. There are many possible combinations using different positions and different tubes, and all of them will have a specific feel/sound. I am a big supporter of searching for "your" sound, I even changed the knobs to have a better overview (the original knobs are imo cheap, ugly and lifeless). I also unsoldered and replaced fx send and return jack plugs to get rid of an unwanted hum/hiss. And finally I started to play with tubes, preamp and poweramp. Power tubes change the character in a more subtle way (kind of like choosing the surface on which you will draw and will you use crayon, charcoal or pastel to make a drawing) while preamp tubes do all sorts of magic with the sound of your guitar and affect the main character of the sound (kind of like they determine what will be drawn).

I've gone trough X, T, Y and U versions of 12a, tried 5751, some vintage ones, tried Ruby and TAD power tubes, even JJ KT66 (but they are just too thick and are virtually touching when installed, so do not buy these). The biggest difference is in swapping position V1 and becomes less significant the further down you go the tube positions, in the end they all impact the sound if you really want to sniff corks. It just depends on if it is worth buying a tube, will it make enough a difference for you to justify the price of it or to be able to appreciate the sound you get.

Then there is option of using different kinds of 12ax7 tubes, large plate models are for example more "musical" but maybe more susceptible to vibrations, like Mullard for example, the ECC83S models are very hard core/rough, you have 7025s that ought to be more resistant to vibrations, you have "frame grid" models (in a normal 12AX7, the grid wire is wound around two posts, on a frame grid tube, the grid wire is wound on a rigid frame, frame grid tubes have very low microphony and tight tolerance) ... and so on.

You decide where you want to start, but go and buy a few different tubes and go to work - invest 100 bucks/euros and buy a few reasonably priced tubes. Start with V1 tube and then move elsewhere - but do your homework and first check which tubes can be used in your amp, but there are many. Your sound will also be determined by the speaker, guitar, cables and so on. I have found that it opened my ears the most when swapping X to T to Y ... it is like having 3 different amps in a way. Try it and see where it takes you, but be patient. Cheers
 
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Sharing some tube swap out results on the lead channel ... all tubes tested are JJs except the AU which was a Northern Electric.

The guitar used is a Player Strat with a roasted maple neck upgrade and Seymour Duncan Cool Rails in the bridge. My cab is a solid mahogany kit from StewMac, holding a 12" Eminence Cannabis Rex.

Lead channel master volume at 9:00, full power setting.

- 12AT7 in V2/V3 - no appreciable difference in the gain sweep, and it sounded harsher to me. Thanks for playing.
- 12AY7 in V2/V3 - a bluesy distortion at 9:00, hard rock at 10-11:00, metal at 11:00 - noon. Tone seemed warmer. That is with both tubes replaced. Individually in either slot wasn't impactful enough for me. I'll keep these handy for sure.
- 5751 in V2/V3 - WINNER! Blues at 8:00, 60s/70s rock at 9:00, 80s power rock at 10:00, and in your face at 11:00 (is this starting to sound like a cruise ship schedule?). Again, best to my ear replacing both tubes. Using neck pickup and gain at 9:30, there's a delicious Sunshine-of-Your-Love-by-Cream tone, which had me glued to my guitar for another hour.

- 12AU7 in V5 for FX loop hiss - I heard of some folks trying this. Wasn't the right solution for the problem - I then swapped out my HOF 2 reverb for a BOSS RV-6. Hiss gone.
 
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