Thanks Vince.

I had an Archon 50 (mkii) that had this same hum with anything plugged into the effects send. PRS screwed me around on the warranty saying they couldn’t replicate the issue. I watched a video recently on Psionic Audio’s channel with a Sonzera and he was commenting that the transistors they used in that amp for the effects loop combined with the topology/execution of the effects loop circuit, it would always have a lot of noise unless the effects loop circuit was fundamentaly changed. The Archon mki had such a pervasive effects loop hum issue that they warrantied a bunch and eventually just incorporated the fix for that into the actual manufacture of later mki Archons. I love PRS amps but I don’t understand why they hell they can’t manufacture an amp with an effects loop that won’t do this. Everyone else, including “lesser” brands have this figured out.

This one did need the shielded otherwise I wouldn't have used it. Some are worse than others. Good you got it fixed for him.

@@amp_mechanic did you try it with the cover back on the amp before adding the shielded wiring?

Mine is the 5881 version as well, 2 weeks old. Definitely a bit of noise. It hums in standby and has a lot of FX loop noise

How could I know which version is the mine one? Thanks, guys!!

@LuismaRamos , just look at the power tubes. Older versions have 6L6 power tubes, and newer versions have 5881 power tubes.

I got my prs mt15 Friday March the 29th it is the 5881 model...it has absolutely no noise at all...thankfully !

@@royrobles7423, awesome to hear....

I own this amp and it's a freaking powerhouse. I have had mine for 2 years and the only issue I've had are with the blue led lights on the clean channel. This is just one video on repair. Go try out the amp and see for yourself. It's great for a lunchbox.

Thanks! It really seems to be a consistency issue. As you note, some are fine. It is unfortunate.

Lol, yes, that’s why the Engl is almost 3 times the money on the used market. I love the MT15. It’s meant to be a super aggressive amp. would expect noise, and you would also expect some corners cut due to price. But yeah, sure if you want to spend the three times the money buddy. Go for it. Also, the other amp tech on KZfaq said this is one of the best built amps. He’s seen. Also, that guy according to his videos seems way more experienced. So I really don’t know who to trust. If you’re going to say, trust the noise, lots of different ants have lots of different noise for different types of issues. You have $3000 Mesa boogie’s that have exorbitant amount of issues. So I guess it’s all in the eyes of the beholder.

The issue is the circuit layout being based off of the Archon but without any consideration for the physical space constraints of a lunchbox. The circuit itself would have been fine but they needed to tweak how parts are layed out on the circuitboard to avoid the electrical interference being picked up by the wires. Most of the time, when you look in any amp, wires get routed on the outer perimeter, or they're generally run away from the circuitboard in the shortest runs possible. The innerds of the MT15 are just a complete mess. Don't even get me started on the linear tapered master volume pot lunacy (I had mine switched to an audio tapered pot to make the volume USABLE). With that said, a noise gate isn't going to solve this problem, internal or on a pedalboard. Believe me, I've tried. The amp sounds great, but the circuit design makes it fundamentally flawed.

Boss ns-2 worked wonders for noise issues in my mt 15 but only when I run it through the fx loop from send/ return on ns-2

Lost any gain/saturation?

@@lovecraftmusic8717 No, it sounds great, it just clean everything You can ear a short sound clip on my last video, in a full mix.

@@ederiel yep, still sounds good, thanks.

Can someone confirms that using lower gain preamp tubes in those spots fix the FX hum?

@@vanespedals1023 i haven't need to... Mine resulted pretty quiet. But to be honest I haven't tried the fx loop yet.

Good to know.

Great!

It sounds like they fixed the issue. I had 2 when they originally came out. The hum was bad enough to make my fillings ache.

I got mine march 29 2024...it is totally quiet...so far

Yes.

​​@@amp_mechanic it looks like the effects loop jacks are isolated from the chassis. Is this correct? If so, how does the send & return jack get ground for their sleeve connection after the wiring modification?

@@danz4904 One of the wires is the ground.

H Brad. I'm in Nova Scotia.

Thanks. Yeah, there's several oddities in the design. Sometimes what works for a prototype or two doesn't work when it comes to full scale production units.

@@amp_mechanic yeah, it’s weird that they didn’t just do some final tweaks and end up with an amazing product. I have the same issues on mine. I’m guessing this operation is not for someone inexperienced? I know how to solder but not worked on amps before.

@@Sperzel If you can dress your leads properly and have good heat control, it's not hard to do. I guess you have to decide if you do get stuck or mess it up, do you have an option to get it to someone who can fix it.

The clean channel is usually silent, and you can remove the lead channel hiss by connecting a noise gate to the effects loop

Check the bias, calculate the actual plate draw. Most of the time I've found the bias will be running hot on at least one or more tubes. There are plenty of other thing it could be but, that's usually my start point. It can also be a bad preamp tube. Easiest way to narrow that down is swap with a know good one and move down the line.

I did for testing it. That may have been off camera. I had shot a clip up about half way but mic was clipping and I didn't feel like grabbing another mic and gaining it down so I just turned the master down and re-recorded.

oh,well, pardon me....lmao. 😂

Yeah, it's not up to PRS standards unfortunately. Hope you can find something to suit your needs.

I'm not a content creator, I have this amp paid for with my own money. I have the newer 5881 version, swapped the fx loop tube for a 12au7 and its very quiet. The tones are phenomenal. I get it's annoying to have to swap out a tube in a brand new amp but to me it's worth it.

I've got one. It's noisy, but it sounds ridiculous. Good clean tone too. 🤷

@@TheMirrorifygreat. Did you fix the noise on lead ?

@@willian5452 I actually had to return my mt15 unfortunately. I think I was convincing myself the noise level was ok because I loved the tones so much but the longer I had it the more it annoyed me. Mine was a hum type of sound, swapping the tube out did lower it but it was still humming at around 30dB constantly. Tried different rooms, hum eliminators, different cables and guitars, nothing worked. The retailer said they were so sick of them coming back they were considering not stocking them anymore.