Tube Layout Chart for MT15?

bubbastain

New Member
Joined
Jul 13, 2018
Messages
14
I’d like to know as well. I did try a 12AT7 in V1 and it was pretty cool. Really gave the gain knob a wider sweep. The gain knob at 10:00 is plenty for me so I don’t mind losing some
 

bubbastain

New Member
Joined
Jul 13, 2018
Messages
14
I do know that from right to left it’s V1, V3,V4, V2, V5 and then V6 is one in the middle.. Would like to know the specific function of each though.
 
Last edited:

bodia

Authorities said.....best leave it.....unsolved
Joined
Jan 21, 2015
Messages
29,799
Location
Suburban Chicago
Got this from Customer Service today. These guys rock!

V1 – input

V2 – lead gain

V3 – lead gain

V4 – clean gain

V5 – phase inverter

V6 – effects loop (behind front row of preamp tubes)
 

Yzerman

New Member
Joined
Feb 5, 2016
Messages
34
Replacing V3 with a 12AT7X does miracles for this amp.... smooths the gain out and helps with the taper. In V2 it was too muddy but V3 was perfect!
 

bubbastain

New Member
Joined
Jul 13, 2018
Messages
14
Got this from Customer Service today. These guys rock!

V1 – input

V2 – lead gain

V3 – lead gain

V4 – clean gain

V5 – phase inverter

V6 – effects loop (behind front row of preamp tubes)

Just wondering if this is from Right to Left or as labeled on the PCB? On the PCB from Right to Left it’s V1, V3, V4, V2, V5 and V6 behind the front row.
 

Yzerman

New Member
Joined
Feb 5, 2016
Messages
34
The one i replaced was the 4-5 gain stage for the lead as per Shawn's drawing...it should be V3.
 

bodia

Authorities said.....best leave it.....unsolved
Joined
Jan 21, 2015
Messages
29,799
Location
Suburban Chicago
Just wondering if this is from Right to Left or as labeled on the PCB? On the PCB from Right to Left it’s V1, V3, V4, V2, V5 and V6 behind the front row.

This was the first sentence in the email I got from Cust Ser

I have listed the preamp tubes below for your reference. They are in order looking at the back of the amp, going left to right (starting at the input). You can change the gain with a 5751 (or a 12AY7).

Shawn inserted a chart in post #9 above
 

Van Noord

New Member
Joined
Aug 4, 2018
Messages
41
Replacing V3 with a 12AT7X does miracles for this amp.... smooths the gain out and helps with the taper. In V2 it was too muddy but V3 was perfect!
THIS!! I did some tube swapping in every preamp spot with a Ruby 12AT7 V3 position yielded the absolute best results. More sweep on the gain dial, and revealed more of the gain's character and feel.
 

andy474x

Knows the Drill
Joined
May 4, 2012
Messages
4,506
Location
West Michigan
For sure! This is my go-to tube swap when I want to bring the gain down on an amp - and all the PRS amps I've played have plenty of it. V1 could even be a nice spot for one, but it would depend on what the effect on the clean channel would be as well, because one half of the V1 tube services on channel, and the other to the other channel. IMO, every tube amp lover should have a little stash of 5751's to play with. The nice thing about them vs a 12at7 is that spec-wise, the 5751 is more like a 12ax7, whereas the 12at7 is relatively much less like a 12ax7. Tonally as well, the 12at7 sounds much thinner and more harsh than a 5751, in the instances I've tried them. Although, I don't think it will hurt anything to use the 12at7 in an instance where the 12ax7 is stock, as the way the specs work, from what I understand, is that the 12at7 can handle more. It's the reverse that can wear down a 12ax7 faster - I read it on the internet, so it must be true. In the spirit of modding something, I suppose if the 12at7 gives you what you want, and it's not hurting anything, by all means, do it. But I still recommend trying the 5751 in those instances as well, just to see what the differences are.

Also, while we're on the topic of the MT15 tube chart, I just want to say how brilliant it is that PRS designed an amp that uses all 12ax7's for the preamp, from a maintenance and gigging point of view. You can just have a few extra 12ax7's and a pair of 6L6's on hand, and if anything takes a crap, you don't have to worry about having a whole selection of tubes on hand. Very convenient. It would be extra nifty if they would add some kind of quick access door to the tubes, to make changes speedy. That and the external bias check would truly make the PRS amps a maintenance and gigging dream.
 

Michael_DK

New Member
Joined
Nov 20, 2012
Messages
845
Location
Denmark
You guys who have swapped some of the tubes out for lower-gain ones - could you try and record some demos of the results? I'd be really interested in hearing how it sounds at various gain levels, it would be a tremendous help :)
 
Top