PRS MT15 Tube Swop

Goran Lorencin said:
You guys are like rocket scientists to me, I`m a newb when it comes to swapping tubes, but have a very sensitive ear and would like to know which tubes (specific model types) are there on offer to be swapped with the factory ones (not to void the warranty and to keep things tidy current wise)? You talk about 12AX7, 12AT7, 5751, ECC83s, 12AX7AC5 HG+, ... god damn where do those names end?! What do they mean? Must I go to Harward tube university to understand all that or? How important is it to use a specific brand/maker tubes?

I just want to find out what options I have when the time comes to swap out some tubes and which tubes I should have at home, ready to be swapped.

What are the alternatives for the JJ EC83S pre-amp tubes?

What are the alternatives for the factory power tubes JJ 6L6GCMS?

I hear many talking that sometimes (Chinese) factory tubes aren`t as good as others made by reputable/other tube makers, how does that equate sound or quality wise?

thx in advance my dear rocket scientists
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No affiliation to this place, but there is a TON of useful knowledge about tubes. Don't be turned off by the 1990s style web page

https://www.audiotubes.com/

Click on the yellow boxes in the middle of the page to begin learning.
 
Brand new to this MT15 saga. Tried a ton of amps yesterday and the MT15 blew me away. What a fantastic sound! Anyhow, a couple things I want to do after reading so much:
1- Get rid of hum in effects loop. What type of tube is the way to go?
2- Tame down the volume a bit. From what I've read, V3? What type of tube? Make? I know all tubes are not the same. Thanks
 
Paul Bouthiller said:
Brand new to this MT15 saga. Tried a ton of amps yesterday and the MT15 blew me away. What a fantastic sound! Anyhow, a couple things I want to do after reading so much:
1- Get rid of hum in effects loop. What type of tube is the way to go?
2- Tame down the volume a bit. From what I've read, V3? What type of tube? Make? I know all tubes are not the same. Thanks
Click to expand...

Regarding the effects loop, there’s not a tube that will fix the hum (at least none that I’ve tried). Best solution I’ve found is the Ebtech/Morley hum eliminator run in the loop. There’s some kind of grounding gremlin in the effects loop, it’s not a tube thing.

To tame the volume, start with a 12at7 phase inverter. I happen to think the amp sounds better with that tube in the PI, as well.
 
I've read that if you put in a lower tube it fixes the hum; but the eliminator sounds like a good idea.

What is a 12at7 phase inverter tube? I've seen some others put a 5751 in there. Just wondering what the difference is, thanks.
 
I've forgotten much of this, but any time you want a lower gain substitute for a 12ax7, a 5751 is the best choice overall. That doesn't mean it will be your favorite but in some amps, the others can cause potential issues... again, don't remember the specifics for certain, but I believe it's the transconductance where the ax7 and 5751 are the same, and the at and ay both are different. This can affect things differently in every circuit, and especially in each position in the chain.

Also, if you push the amp hard, the effect of a lower gain PI tube will vary dramatically depending on the amp circuit. In an amp like a Plexi, where the PI overdriving is part of the magic (and the one that people think is the power stage overdriving but it's not, it's the PI) I wouldn't ever consider a lower gain/higher headroom PI tube. In something like an MT-15 or other high gain amp where much of the tone is derived from the preamp stages, it's a much more viable option.

And again, I'm not saying you can't replace any of these tubes in the chain with a 5751, at7 or ay7, but there are some differences in the tubes which can affect things other than tone and gain.
 
FWIW, I changed out all preamp tubes to 12AY7's except for V2 (5751), the Effects Loop (12AX7), and Phase Inverter (12AX7). Very happy with the results - Cleaner cleans and a much more "Marshally" red channel akin to a DSL.
 
Britt Landrum said:
FWIW, I changed out all preamp tubes to 12AY7's except for V2 (5751), the Effects Loop (12AX7), and Phase Inverter (12AX7). Very happy with the results - Cleaner cleans and a much more "Marshally" red channel akin to a DSL.
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It's cool that you got results you like!
 
[QUOTE="Very happy with the results - Cleaner cleans and a much more "Marshally" red channel akin to a DSL.[/QUOTE]

Just curious - why would someone buy this amp with intentions to make it sound like a Marshall? Out of the box, this amp is aggressive with a powerful low end - which is why I bought it.
 
Paul Bouthiller said:
Brand new to this MT15 saga. Tried a ton of amps yesterday and the MT15 blew me away. What a fantastic sound! Anyhow, a couple things I want to do after reading so much:
1- Get rid of hum in effects loop. What type of tube is the way to go?
2- Tame down the volume a bit. From what I've read, V3? What type of tube? Make? I know all tubes are not the same. Thanks
Click to expand...
Yep, the MT15 is a small beast, it won me over in a glimpse, and the price I got it for was also good.
Regarding what andy474x said about the tubes and the FX loop hum, I must say I disagree, although at first I also thought that the noise was there to stay. In my case, after fiddling around with tubes (replacing one bad JJ, replacing two other original JJ tubes with a 12ax7 Mullard and a TAD 5751) made a surprisingly big drop in FX loop noise, that much so that I started using the 4 cable method again and it works like a charm, or at least it did the last few times I played ... hope it stays that way the next time I play ;) I also put rubber dampers on most of the tubes (for that pinch of more assurance). I think I also wrote in one post in which positions I have the new tubes. I must say that I was also surprised at the result, replacing the bad preamp tube also lowered the overall noise by quite a lot, am very satisfied now that I can use the FX loop, now the Sentry does its noise suppressing job on the lead channel as well, which is just f-ing awesome ... you do the chugah-chugah-chugah and when you stop it is silent. So I just want to say that it is (apparently) possible to fix the FX loop issue for which I also thought I would not find a remedy.https://forums.prsguitars.com/members/andy474x.1237/
 
Paul Bouthiller said:
Just curious - why would someone buy this amp with intentions to make it sound like a Marshall?
Click to expand...

BC I prefer the Marshall preamp sound running on 6L6's, the portability, the low wattage, the specs, and the price point of the MT15.

Wanted to share my latest find...KT66's in this amp add even more low end and additional crunch. Absolutely love the sound I am getting now!
 
Well now that I've swapped and tried a few different preamp tubes I must say they make a lotta difference, but want to also add that swapping power tubes also makes a difference in character, for example I prefer the original Ruby 6L6GSCM over TAD 6L6GC's that I also bought just to have a backup. They all sound ok, but the TADs are more Marshally (fine grain) and Rubys are sort of more visceral (coarse grain).
 
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