Mt15 HIss ( NOT HUM) issue

[Bmw9786]

Hey guys I got my amp yesterday plugged it in and let it warm up played both channels and they worked great so I stayed on the dirty channel for a while then switch back to clean and all of a sudden I had a tremendous amount of static and hiss that gets louder/quieter as you touch the volume control for the clean channel.. the dirty channel is fine... this is not the hum issue everyone else is having... did all the regular checks for guitars,cables.. it’s the amp and it’s the clean channel specifically.. please help..

 

[brokenromeo]

Probably an issue with one or more preamp tubes

 

[László]

Sounds like a preamp tube. If the amp is new, and it’s bad, PRS will probably replace the tube at no charge. You should call your dealer.

 

[bodia]

Sounds like a preamp tube. If the amp is new, and it’s bad, PRS will probably replace the tube at no charge. You should call your dealer.

This!

 

[SJP]

I just got my MT-15 the other day here in the US. I have seen many threads about the hum, buzz, noise issues but I still purchased it any way and I have this same issue as well.
With nothing plugged in, except the speaker cab and amp, on the clean channel it has some hum at high volume with is normal on any amp. On the lead channel it has this static noise (not buzz). The only way I can describe it is if you are on a AM Radio station and not tuned into the right channel you here static. this static starts as soon as you start turning up the lead volume at 1 and it gets very loud by 5. Anyone else experiencing this issue?

 

[brokenromeo]

Where is the gain knob set at...I would say that is normal high gain hiss...the only way to get that quiet is to use a noise gate. Completely normal for a high gain amp tube amp...

 

[SJP]

its the same as the lead volume, as you start turning up the gain knob it gets louder...you hear the static from 1 volume 1 gain and it gets louder as you raise it...on 15 w & 7 watts

 

[brokenromeo]

Yup, sounds like normal gain hiss...you might be able to quiet it down a bit with carefully selected preamp tubes, but it will only be a nominal change. You will need to put some sort of noise gate in the effects loop if you want to tame the high gain hiss. This is normal...as long as it isn't doing it on the clean channel too.

 

[SJP]

I'm not used to this static noise, I also use a Mesa Single Rectifier and I tested it yesterday and the hiss starts when the output and lead volume hit about 4 and gain 3/4 up...not an issue though because I don't play at that high volume so it's super quiet at around 2 to 3 volume. but this MT 15 starts to make noise at 1 volume and 1 gain...I' m trying to play at 2 on lead volume and 3/4 up on gain and it sounds like there is a friggin radio next to my cabinet blaring on AM frequency not tuned to the right station...annoying as hell. this can't be normal.

 

[brokenromeo]

Well, that level of hiss does not sound normal...I would contact PRS for help. It could be one or more of the preamp tubes causing excessive noise...if you have some known good preamp tubes laying around, you might swap some out to isolate where the noise is coming from. I think there is a tube diagram floating around on the forum...

 

[SJP]

This MT 15 is brand new but not bought directly from a store... bought online and it was delivered by UPS so who knows what package went through but it didn't look damaged.

 

[brokenromeo]

Tube damage can occur in shipping, you might also want to check that all of the tubes are properly seated...

 

[SJP]

it's possible, sucks that you get a brand new piece of equipment and you have to start taking it apart to fix issues. I noticed with the volume down to 0 you get the slight buzz,hum in the speaker cab with the MT15 and my Mesa Single Rec, I also get the same buzz coming through my Bose system so that must be from the circuitry in the house. But that static is crazy when you start turning up the lead volume and gain...the clean channel is sounds amazing and quiet. Overall it sounds amazing and loud as hell. One thing the MT15 is missing is the output level/knob for the volume. Even at 7watts if you want to jam quietly , 1 is too loud on lead volume...if you turn it down just slightly you are at 0...it would be great to have to leave the lead volume at 1 and have that output level/knob to fine tune/adjust the lead volume or clean volume. Is there anything out there I can use to control the volume if the amp doesn't have an output level/knob?

 

[Lonnie L Zamarripa]

I just got my MT-15 the other day here in the US. I have seen many threads about the hum, buzz, noise issues but I still purchased it any way and I have this same issue as well.
With nothing plugged in, except the speaker cab and amp, on the clean channel it has some hum at high volume with is normal on any amp. On the lead channel it has this static noise (not buzz). The only way I can describe it is if you are on a AM Radio station and not tuned into the right channel you here static. this static starts as soon as you start turning up the lead volume at 1 and it gets very loud by 5. Anyone else experiencing this issue?

Yes , I just purchased a new MT 15 at Gearfest. I set it up Saturday morning. At first I had a lot of 60 cycle hum. Moved it to another outlet and the hum was barely noticeable. So when I flipped the switch to lead the hiss makes the gain channel unusable. You would not be able to use it in a studio . Mind you I have not switched to 15 watts yet. When I did my wife came straight up out of her chair complete with expletives. The hiss is not a problem in the clean channel. I will be calling Sweetwater tech support tomorrow. Any ideas appreciated.