PRS MT15 Modifications

[@danz4904]

When you marked the holes for the new handle, you should have positioned the metal parts so they were against the inner edge of their handle slots. Mounting them closer together would allow the handle to pull up higher.

[@Lack0]

ECC83S = 7025 is a high gain 12ax7. So any regular 12ax7 would reduce gain in the amp. The TAD 5751 is the first choice to improve clarity, smoothness, tame vintage character. It has 25% less gain than standard 12ax7. The RUBY 12AX7WBC has 4dB less gain than a 12ax7 and noiseless, open sounding. TAD ECC803S is a long plate 12ax7 in the tradition of the famous Telefunken ECC803S. It has 1 dB less gain, very detailed and defined. Ideal for the audio driver stage (PI), strong cathode current. TAD ECC83WA Is a regular 12ax7 with a very unique mid focused gain. Very low noise, slightly less gain, soft highs and edgy dominant mids, crispy and more vivid tone. One of my favourites. And the best sounding 12ax7 IMO is the Tungsram ECC83. It has tapered mellow highs, well defined but solid lows, extended frequency range, very balanced. Chiming cleans, punchy chords, singing leads. super low noise and no microphonics issues Tube Amp Doctor says: Sound wise they are much alike the original UK made Mullard, smooth, with slightly extra air in the top end. A fabolous rich midrange is the signature character of the Tungsram 12AX7 / ECC83. I have all these tubes and use them to tame gainy amps. I would never put a 12au7 /12at7 into a circuit designed for 12ax7.

[@nicosanchez_music]

Appreciate the info on this!

[@dvdpz89]

I did the same exact thing to my handle. Only thing I would change is bring in the mounts closer together so I can actually fit my hand in without my knuckles rubbing the top.

[@digitalreign7485]

Agree with you. Mine is a bit snug as well.

[@josephkirk939]

Could you possible make a video on how to repair the red and blue leds on this amp? It seems to be a common problem with these amps and no good videos on how to repair them. Thank you. ​@@digitalreign7485

[@johnmacqueen3811]

I'm a standup and electric bassist who wanted a dedicated guitar head on the side. A pleasant surprise is how great it sounds with my standup for straight up jazz with a '70s era Underwood bridge pickup. I no longer have any nagging doubts about getting this head ( vs say a Blues Junior) since I have the option run it through my EA 1x10 bass cab or with my PRS baritone guitar through the same rig ( cab driver has a concentric tweeter.) Its just a hair shy on bass for my old Jazz bass but sounds great as well.

[@jeffvanbibber6609]

I replaced my handle over a year ago. Worked out great.

[@robtoc]

This was a great post...thank you! I ordered one of these from Sweetwater...it's on backorder right now.

[@digitalreign7485]

Much appreciated Robbie. Hope you enjoy it as much as I do. Cheers!

[@L.Scott_Music]

The handle mounting brackets should be slid towards the inside of the strap slots so that once installed the handle can bend up more for the hand to grip, but then slides out so the handle can sit flat. That is, if you had drilled the left and right bolt holes a 1/4"-1/2" closer together the handle would function a little better.

[@digitalreign7485]

Good advise. Someone else posted they did a similar thing to me and wish they had a bit more leverage with the handle.

[@ronnieparfait]

@@digitalreign7485 can’t do anything about it now.. unless you can maybe find a leather handle longer or get a custom handle made. Good job nonetheless.

[@stevenorton9438]

Hey so I took yr view with the preamp tubes I swap them out with what you said omg what a difference it's alot more usable thanks

[@digitalreign7485]

Hey Steve, Glad to here it brother. I feel the same way. Cheers!

[@thomasVA9707]

😂😂😂Sorry I'm laughing but you were supposed to drill your holes closer to each other to the middle so that the handle can pull up when you get your hand in when you lift it, i love what you did with the valves, i might try it in future but right now im over the moon with the standard sound, a demo of your sound with those two changed valves against the two old ones would be very appreciated

[@kurtj312]

I own 2 of these. One is amazing the other is lifeless (missing the rich complex harmonics in the clean channel). There are differences from the factory (an added capacitor) and there are always variants in the tolerances of parts. So, I use the 2nd as s slave for a stereo setup. I run Genalex 12AX7s and TungSol 6L6GCs. Yup, my gain on the lead sits about 9 o'clock.

[@digitalreign7485]

Kurt that’s interesting. I have also owned two of these amps but not at the same time. I wonder what specifically is the main difference that causes one to be fantastic and the other one not so much. As you said it could come down to the parts tolerances. Do you think the capacitor addition is adding those harmonics? Do you have a video comparing your two models? I would like to hear that. Cheers!

[@kurtj312]

@@digitalreign7485 It'll be a couple days, but I'll demo them for you. Kurt

[@digitalreign7485]

@@kurtj312 Nice! Looking forward to it.

[@nomadronin7361]

I had 1 and it definitely didn’t sound like the demos I hear on YT. It was very dark and got muddy very easily. I really wanted to like it but I just couldn’t get a tone I liked out of it and ended up selling it. Been thinking about trying one again to see if maybe it was just the one I had so it’s interesting to me that you had a similar experience.

[@kurtj312]

@@nomadronin7361 yeah that's exactly what I had. Sterile & lifeless. I have 2 now that, even while clean, harmonics justsing.

[@mike1967sam]

O yeah I forgot, I have this amp and I have it on very solid authority that the PRS MT15 is NOT 15 watts it's 24.29 watts on full mode and 11.4 watts on half mode not 7 watts. I mean just think of it 6L6 tubes normally put out a minimum of 25 watts so it makes sense.

[@digitalreign7485]

Without a doubt! I love the 6L6 grit though and for me is the purge right amp for gigging. It has all the low end punch with not an over abundance of wattages. Twenty four watts ids really ideal for club level volumes in most cases.

[@waitin4winter]

That is awesome. I used 550 paracord and created a wrap around the stock handle. It helps some, but at least no drilling was required.

[@digitalreign7485]

Yeah that is a good idea and I bet it does help with the feel of the handle. Cheers!

[@metalliholic]

Awesome Mod, About the tubes, do you need to rebias the amp if you make those changes?

[@digitalreign7485]

No. Only if you change out the power tubes. Then I suggest at the very least checking the bias and adjusting as needed. Cheers!

[@paulkielt9301]

To me a 12AT7 is a good choice as a Phase Inverter tube.

[@lorencing]

Nice mod if you need it, personally I feel that the original handle is ok, it's not like I will be putting stuff on top of the amp. But I did other modifications like different knobs and tubes.

[@huddleshuddles7360]

Is there a volume pot mod... this amp gets way too loud with micro adjustments.

[@digitalreign7485]

I haven’t looked into it. I have see folks adjust Fender Hot Rod Deluxe amps by putting in a 12AT7 or the like in the V1 slot to help with the “way too loud” volume knob with some success. You might try that for a less expensive fix.

[@michaelbarber590]

It has an audio taper pot (like the Fender Hotrod Deluxe and Deville). You can add a linear taper pot instead, but you may or may not be as happy with the sound.

[@itsmechris14]

JHS little black pedal box

[@jayteesgear]

Very interesting. I played these when they came out and dismissed it cuz the Gain was wayyy too intense but tried a NEW one and it has 5881 in place of the 6L6’s… I found the clean channel to rival a Victory preamp I have (which is AWESOME) but could NOT dial the Bottom end out of the Gain channel- any thoughts or advice?

[@digitalreign7485]

Hey Jay. I plan on comparing both the 5881 and 6L6 power tubes very soon. I believe what you say is correct. The 5881 seem to breakup even sooner than the 6L6’s. I’m interested to hear exactly how much when I shoot that video. The bottom end on the amp is very pronounced and is one of the main things I love about the amp. Too things I think help dial it in. Firstly, you need a really good speaker cabinet to hold that bottom end. I use avatar oversized 1x12 cabs and they are fantastic. Secondly, on the red channel I dial back the gain to around 10 o’clock to tighten up the sound and keep it from remotely getting muddy. Cheers!

[@typangtv]

Tubescreamer

[@KipCount]

Do you have any trouble with the FX loop being noisy?

[@digitalreign7485]

Hey Kip. I have had no troubles at all with the fx loop. The only issue I have had with the Amp is the footswitch pedal cable is shorting out and I now have to use my Orange pedal in it’s place.

[@donewithmodernlife]

I’ve had that problem but it’s dependent on the pedals I have in the loop. The amp only seems to like higher end pedals (Strymons work well, EHX & Ibanez cause noise.) When I run 4cm with my HX Effects & an active buffer in the loop it’s dead quiet though.

[@mrvabilene4971]

The oil off your fingers can in some instances can cause the tube to heat up more, especially on output tubes. Take it or leave it. Why not keep the tubes as clean as possible.

[@journeytree]

because it doesn't really matter that much

[@griffsimcox9459]

I have a 6505 mh that had the same "insane gain" issue 5751s all around made a huge difference. sadly they have a solid state phase inverter so no swapping that .... oh and nice handle :)

[@digitalreign7485]

Awesome! Glad to hear that it also works well on other high gain amps in the same vein. Cheers!

[@erpringle]

You need to change the v1, J.S. A tungsol 12ax7 works really good but I found that the cv4004 genalex works even better to my liking. Sorry but unless you're poor, IMO JJ'S suck, sorry just my opinion. You should definitely try changing the v1, it makes the biggest difference. Also I don't know about the at7 for the pi because it's designed for ax7, and this is just me but I think the 5751 would be a better candidate as long as it's balanced, for the phase inverter position. I am a firm believer in tube rollin. I love your videos and just found them as I just bought this amp and I like a lot. Just subsribed.

[@digitalreign7485]

I have a tungsol in v1 of my Marshall mini-plexi and it has great breakup in that amp. I have swapped a bunch of tubes into v1 of the mt15 and still prefer the consistency and noise floor of the JJ’s. Agreed there are better tubes than the JJ’s but for the money they are very consistent with good reliability IMO.

[@sfrozen1990]

I got this amp. Great sound, but when i try to plug an external switcher (from my master pedalboard) to change channel, It makes a very loud hum noise... What's the problem?

[@digitalreign7485]

I’m no expert on that stuff. But you might check to see if you have some sort of ground loop. The hum noise to me usually indicates some sort of ground issues.

[@nathanielroy5086]

Did you use a TRS cable? Let me know if you fix it, I was planning to do a similar setup with my amp when it arrives in 2 weeks

[@sfrozen1990]

I fix It with a behringer hum destroyer put in front of the amp's input. I think the problem is in the Power circuitation of the amp itself...

[@paisteplayer1040]

I played mine next to my bogner 3534 and mesa mark V35 neither amp was louder or fuller sounding than the mt15.

[@digitalreign7485]

Which one did you prefer the most and why?

[@paisteplayer1040]

The Mt15

[@paisteplayer1040]

@@digitalreign7485 They had have their pluses and minus'. The mt15 is easiest to dial in a nd sounds great, and they are super cheap used..

[@ivanzivanovic4013]

Can I replace the 6L6 tubes with a matched set of 5881s or does the swap need biasing per amp?

[@digitalreign7485]

Hey Ivan. Yes, the 6L6 and the 5881 power tubes are interchangeable. However, it is recommended to re-bias the amp since the 6L^ tubes have a higher wattage and plate voltage than the 5881. Cheers!

[@ivanzivanovic4013]

Yep I should have finished your vid first 🤦🏻‍♂️…

[@GoudVis56667]

I have some minor problems with the clean channel on this amp. The red channel is way louder than the blue so when I try too match the clean volume it starts to break up and then its not clean anymore haha. My pickups are quite hot so does it help to put a lower output tube in the clean channel slot? Also thinking about replacing the output transformer to make it a 50Watt amp and putting a master volume on it but that will costs alot more money.

[@digitalreign7485]

Hey Goud! Yeah that is definitely a thing with this amp between the clean and lead channels. When I play this amp live I set the clean channel volume first then match the lead channel volume wise. Im always mixed up when I play live so cranking up the amp isn’t really something that I’m having to fight through. As far as the clean channel break up, do you pull out the boost for a pushed clean? That will cause it to break up sooner for sure. In my experience this amp has a very clean channel that actually stays fairly clean. If you wanted more headroom the 50 watt transformer would give you that extra clean headroom. I would first try some lower gain pickups. I’m a fan of slighter hotter than normal pickups but I’m a fan of getting the gain from the amp like the MT15. This amp has the gain in spades! Cheers.

[@GoudVis56667]

@@digitalreign7485 I never toutch the build in boost because its already breaking up haha. Will a lower ouput preamp tube work to keep the clean channel break up less? If not im gonna take it to a tech and mod it.

[@chusamusic1409]

Pull the clean channels treble nob and lower the gain on the red channel.

[@GoudVis56667]

@@chusamusic1409 I need less breakup on the clean channel not more...

[@azarea]

@@GoudVis56667 Yeah, putting a 5751 in V1 will reduce gain in both clean and lead channel (making the gain pot more progressive on the lead channel and reducing breakup on the clean). Alternatively you can replace V2 if you only want the clean touched up. It's a 20 bucks "mod". Keep in mind reducing the gain on the clean channel will reduce volume as well, as it's not as compressed as a distorted channel.

[@fstnfurz]

Handle looks awesome man!🤘🏻 I’m gonna do the same to mine. Where did you get the handle at?

[@digitalreign7485]

I purchased it on Amazon. Link should be in the description of all the parts I used. Hopefully it still works. Cheers!

[@bigtorrisi]

FYI power tubes can hold charge for several days after they have been removed, and this charge can be fatal.

[@digitalreign7485]

I was always taught that the filter caps hold the charge up to 400-500 Volts potentially and should be drained before any work within the amp itself. Always take caution and unplug the amp for anything you are doing as it is “hot” when plugged in. Cheers!

[@lorencing]

I'm no electrician, but the tubes by themselves do not hold any charge, the capacitors on the other hand do.

[@bigtorrisi]

@@lorencing You're wrong there dude, it is the tube that holds the charge.

[@lorencing]

@@bigtorrisi looks like you are also not an electrician. If what you say was true, then I would have to be dead a couple of times. Tubes can not hold charge, capacitors (as the name suggests) hold capacity that can kill you, so it is them you have to drain before working on a tube amp. The tubes are basically glorified light bulbs ... that make use of that charge in the capacitors.

[@bigtorrisi]

@@lorencing Ill have you know I am one of the greatest electricians ever in the whole world. Anyway that aside, Im def right.

[@PhuketMyMac]

Have you been able to compare the PRS MT15 with a Mesa Rectifier? I haven’t done any tube swaps yet and I am wondering if I should. I use to love my Recto. Now that I have the MT15 I feel it has too much gain and can be muddy. Since I play punk rock like you, I would love to have more versatility with more options in crunch, hard rock territory. Once reaching 3, the gain is beyond my liking. Since we’re playing the same, have you been satisfied with the MT15 once the tube swap was done? I am asking cause I am tempted to swap my PRS with a recto.

[@digitalreign7485]

Hey Phuket. I have not done a direct comparison between the two. But I believe Sonic Drive Studio’s did a comparison a while back you should check out. That dude’s videos and quality are top notch. I’m in the camp as you are in regards to the Rectos. Too muddy for my tastes, I love all the recorded tones through them in the 90’s but I was never able to replicate them on my own. Check out a few of my other videos I did where I replace the preamp tubes on a few of the gain stages to 5751 and 12AT7’s to take off a bit of the over saturation and give you a little more headroom. I gig this amp regularly with the tube swaps and swear by it for added versatility in club gigs. Volume with the amp has never been a problem. Cheers!

[@dangitdan9938]

So what I hear is “great amp but doesn’t like pedals, especially fuzz” No fuzz is no bueno. 🙁 Any truth to this or does it actually take pedals well?

[@digitalreign7485]

The amp actually works really good with pedals. Fuzz pedals can be a tricky mistress though. If you are going to run fuzz into the MT15 I would suggest a Muff style one into the clean "blue" channel of the amp. For my taste the Red channel has too much gain to accept fuzz very well. If you where to back down the gain as much as possible and add a touch of fuzz with a bit of volume boost to the red channel then you might have something with good saturated lead tone. This is a good topic and one I think I will make a video about. Thanks for the comment Dangitdan and be on the look at for the MT15 Fuzz video. Cheers!

[@donewithmodernlife]

Mine works great with fuzz, drive channel included. A good octave fuzz seems to work especially well & gives me a killer lead tone. I do have a 12AT7 in v3 so my lead channel is much more useable & has about 20% less gain than the stock config.

[@theshape2153]

I can’t believe you touched the tubes.😆 just kidding.

[@werojas]

Hi... Are all tubes normal or are there any balanced?

[@digitalreign7485]

Hi Welfram. I’m not understanding your question. The power tubes are balanced but the preamp tubes are not necessarily balanced and as stated in. The video they have different levels of gain based on the different tube types.

[@lookslikemeband]

Subbed!

[@digitalreign7485]

Much appreciated!

[@howardgillingham4763]

That's added more boost and 10 more watts

[@digitalreign7485]

A really good guitar player can make it seem that way! Unfortunately that isn’t me! Cheers.

[@AJC-jo3ds]

PRS Tech Support confirms that V5 is the Phase Inverter and V6 is Effects Loop…

[@digitalreign7485]

Thanks for confirmation. Cheers!

[@nicosanchez_music]

Wait so is the phase inverter still the one in the middle row singled out between the power tubes and pre amps????

[@pedrolourenco2707]

you call this modifications, you should see teh inside of my Mt15! though it sounds better than any other Mt15 on the universe :D

[@digitalreign7485]

Excellent! What mods have you done to yours?

[@pedrolourenco2707]

@@digitalreign7485 first coupling cap to 680pf, treble boost by bypassing grid resistor with 220pf+200k, cold clipper to 10k (next stage grid resistor to 220k), last cathode bypass to 1uf!

[@digitalreign7485]

@@pedrolourenco2707 Hey Pedro. Have you uploaded a video of these mods? Would love to hear what you're hearing to improve the amp. Cheers!

[@johanhofstedt7317]

Pedro i´d love to se a video about what you did and how it sounds!!!

[@darkhorseO3]

Dude you screwed up the handle holes. You should have made them closer together to allow the handle to bow

[@digitalreign7485]

Yeah I agree. In hindsight that would of been better.

[@kraken8159]

Should of used a tape measure to center your handle install?🤣

[@digitalreign7485]

I used an engineering scale….it looks fairly centered! Cheers!

[@bernardfoshage9901]

Touching tubes with your bare hands is just fine. It's light bulbs, especially automotive, that get magma hot that you don't want to touch. Tubes don't get that hot.

[@a-nus]

Crank your amp for an hour and touch the tubes then report back

[@brettphillips2309]

Why did prs start using 5881 instead of 6l6 ? Mark is a 6l6 guy so this doesn’t make sense

[@digitalreign7485]

From what I heard through a KZbin video is that the 6L6 factory burned down and PRS convinced Mark to try the 5881 tubes.

[@TheBluesine]

Modifying the handle is just stupid! . Its unnecessary because the head is not heavy......

[@digitalreign7485]

Hey CP. I replaced it for comfort reasons not due to the weight of the head. It’s a lunchbox amp after all! Cheers!

[@bripolar]

Ur stupid

[@mike1967sam]

Did not catch your name so I'll just call you dude...dude that handle is a pain in the ass because you can't lower it, but a lot of Orange 15 watt and even 30 watt amps have that same handle.

[@digitalreign7485]

Hey purple haze! Hey man my name is Jeff. I completely agree the handle is a pain in the ass and super uncomfortable to carry and so that is why I replaced it. I recommend doing it yourself. It was a super easy mod and worth the time in doing it. Cheer bud!

[@mikehunty20]

Good thing is, you can't make it any worse.

[@tomix1970pl1]

Paint his nails next time.

[@Fuzzybunny-ki1cw]

"what's crack a lackin" ewwww unsubed

[@workdays8280]

This amp is nothing but a toy to my Black face fender twin. Absolute junk. And U turn it up gets no better only louder. I believe it's not even a real valve amp. It's a solid state amp. And no reverb so U need to add $300 on top for a reverb unit. Then $1200 for a 2x12 speaker. Total Chinese junk. These people on Anderson make this amp sound unreal but it is not like 100%

[@andremessias2974]

Troll alert !!!