DGT 15 boost very noisy if master not engaged

[Dingoe_ed]

Hello searched some, but didn't see my issue discussed. Truly appreciate any input.

I just received the amp last night and right away notice the higher noise level compared to my '71 Pro Reverb and my Blues JR.

I'll test the amp today at higher vol and try a meter on it, but has anyone else had this issue.

Issue 1. I can have the Vol and Master all the way down, have the guitars vols and tones all the way down. Turn on boots with master off and the noise is bad. Roll Amp VOL up and gets so bad you can't play over it.

Boost toggled ON ( or engaged with foot switch), and Master toggled OFF = noise levels rendering the amp unusable for the most part.

The only way to make the boost work without a lot of hum/fuzz bad type noise is to run the master and bring it way back to quite the noise, but making the amp just sound small.

Tried DGs settings and the hum/fuzz noise level was crazy even before touching the guitar. Watched David's demo and his was definitely not like this one.

My other tube amps only make typical amp noise when turning up, but this one is not going well. I might plug in my 71 Pro Reverb 212 with 4 ohm setting and see if that changes things.

Issue 2. Loud Popping on shutdown: On my other amps I turn VOL (master if has one), off before shutting down the amp and no pops or extremely low. This DGT 15 pops extremely loud almost to the point of worry?

I truly appreciate any help with this. I'll test the amp again today and try a meter, but if V5/V6 show close numbers, not sure what to think.

 

[RickP]

You didn’t mention if the amp was new or used, but in either case a call the PRS support would serve you well. You should get no more noise using David’s settings than David did, so that points to an issue. If it’s new, might be a return or swap thing for fastest resolution. If used, you’ll need to go through a troubleshooting process checking preamp tubes and such.

 

[Dingoe_ed]

Thanks for the reply Rick.
Yes it was used thru big chain's gear exchange.

Tubes don't sound microphonic, but I'll have to open the back to tap them. But will definitely reach out to PRS today after I have a full list of issues.

Just seems like a lot of noice with the boost. If I just run no boost and use a BD2, it's fine but was really liking the idea of no peddles.

Thanks Ed

 

[László]

I'd have to agree with Rick; there shouldn't be a noise problem. If you're not sure about troubleshooting tubes, most Mesa owner's manuals come with very good suggestions on how to do it.

Sometimes a noisy tube doesn't show up via the tap test. The surest way is to replace them one at a time with a known good tube, and if the tube that's removed doesn't change the noise, put it back where it started and move on to the next tube.

It's definitely a pain in the rear to do it, but it works.

It's also possible to have a noisy output tube. If the preamp tubes are fine, replace them with a matched set of known good tubes and re-bias the amp to spec see if that helps.

If nothing works, the amp might need to be serviced by PRS.

 

[Dingoe_ed]

Thanks for the tube test solution. I use to do that with my old Amps and I have some here. I think I have the V1 tube from my Pro Reverb to can use for the 12ax7 and think I have an AT in the amp I can just pull to use as a test.

Going to test the output tubes with my meter thru the test jacks they have in the back of the amp.

Got a reply from the original owner (he had it for about 8 months or so and was also using a PRS DGT 1x12 cab). He said he noticed a louder powerdown as it has no standby, but he said he'd let it sit a moment or two after use, Vol/Master down and wasn't as noticeable. He said he wasn't having any hum issues though.

I'll post what I find here in a bit. Had to work on the truck today, but amps coming first.

Thanks Ed

 

[Dingoe_ed]

Did some tests.

Tap test good, so I'll pull each tube check with meter and do tube swaps as test like Laszlo suggests.

I get about 30 - 33 on the bias jacks. Manual states +/- 35 approximately, so that makes me think they are good. I'll pull and check with meter. Does anyone know what pins are the heaters on JJ EL84s? I assume I have good continuity because I got close to what manual states. But figured I'll check um.

After that not sure. Seems to just be a bit noisy and especially with boost tripped and Master OFF.

Think my ears are getting use to the hum too, because now playing I just don't think about till I stop and let the amp just run.

Still has loud shutdown pop even when I let it sit for a bit and I hear people say that's a tube issue, so I'll keep checking things.

 

[László]

You probably already do this, but I'll mention it anyway, because folks sometimes forget to (I've forgotten it myself on occasion):

When checking for noise, always disconnect the guitar and any pedals, including pedals in an effects loop, if there is one. That way the only noise you're hearing is coming only from the amp, and not from other gear.

Although my PRS amps are US CAD models, they're the quietest amps I've ever owned. My Mesa amps are silent as well. I'm super-careful about proper grounding, isolated AC outlets for the amps, isolated outlets on pedal power supplies, etc.

I can have all four of my amps turned on and set up for sessions using my amp switcher and mics, and have zero noise. I'll admit I'm kind of loony about hum and noise, but I'm in the music biz and can't have noise while recording.

 

[Dingoe_ed]

Thanks Laszlo, I hear ya and though I can play over the hum/static, it's not right and I'm a stickler for trying to get stuff right. Plus, my buddy that performs will right away say " that amps too noisy", I know he'll like the tone, but he wants Amos that are silent when just sitting.

I did as you said and isolated it from everything, but I'm going to move it to a different room today try that and also pull some EL34s from my small blues jr and see if those help.

I really think it's something in the master circuit. When I use the mastery and roll up to about 12 - 1 o'clock approx. I can get all the hum and static out. Beyond that it's back or amplified by the volume push.

Thing is it should work without a master running with the boost on, so I'll keep troubleshooting till I have to take it to the shop.

Thanks again for the help PRS said they will respond to my email in a week or so.

 

[Dingoe_ed]

Well tried all I can do.
EL84s from Blue jr, no change.

Different rooms electrical, no change.

Pulled the chassis everything looks good as far as I can tell.

Called PRS today sent videos. They're shorthanded, so could be a week or so.

Have 4 days to decide to keep it or pay to ship it back. Was such a deal on SW gear exchange, I'm keeping the amp can always have a tech try to quite it up later. Plus, if I don't run the boost it sounds great. With boost still sounds great, you just hear the amp noise. Actually I think I'm hearing it less and less, must be getting use to it.

Thanks again to all for input.
Ed

 

[Rollylama]

Have to ask....was any of this testing done without anything plugged into the amp input?

 

[Dingoe_ed]

Yes you can have just the amp and speaker cab stand alone with nothing plugged in and it's the same level as when gear is plugged in.

It's just a noisy amp, or at least mine is.

Spoke with a tech and he said he'll help to bring the unwanted noise down once and if I decide to reduce it.

Right now I'm just using the boost only with master and that's fine it's good enough for home use.