Mark V:25 noise and retube question

[kgbstrat]

Lately, My Mark V:25 Channel 2 has gotten very noisy. Gets worse when signal is driven harder, e.g. TC Spark boost pedal. Had a similar issue a long time ago that disappeared, but now is back. Tried all sorts of trial/error things, different cables, FX loop connected/disconnected, wired vs wireless, through the pedal board vs direct, different power cable, different power strip vs Furman power conditioner. dialed back gain (which is not that high to begin with, maybe around 11:00) - helps some, but still there. Same with Mark IV vs IIc+ modes (IIc+ a little less). Obviously the more gain, the worse the noise. Note, was not this bad a few weeks ago. I am assuming the tubes might be going, but other than the noise, the amp tone is great. I uploaded a video of the noise in the hopes that someone can say it's due to the preamp vs power tubes. I am at a loss and want to be sure before I buy a whole retube kit that I may/may not need.



Note, if I do retube, I noticed several stores that offer a kit mention a balanced 12ax7 in V6. However, I don't see any mention of that with Mesa themselves. Any issue with just getting 6 12ax7's (likely get the SPAX7's since they're not that much more) vs a retube kit (likely JJs) with a balanced one in V6? Or, are you supposed to use a Mesa 12AT7 in V6 since that is mentioned as a phase inverter tube?

 

[esowden]

I wouldn't worry about a balanced preamp tube for V6. I've never been able to tell a difference in tone in that respect, though some say they can. I wouldn't do a wholesale retube either - try switching individual preamp tubes with a (known) good tube to see if it's tube related. (Probably is but may not be.) Since channel 2 seems to be the one with the issue, I'd check V1, V2, V3 and V5 in that order. Noisy power tubes tend to be noisy regardless of which channel you're using.

 

[kgbstrat]

Ugh. Complete retube. Mesa SPAX7's and paired EL84's and noise is still there. Noise exists going direct or via the wireless. Definitely worse with the pedal board (4 cable method, fx loop in/out makes no difference, front chain adds more noise). Diagnosing the pedal board to see if any particular pedal is the issue. So far, no luck. At a loss. Using a fairly new Voodoo Labs Pedal Power 2 (isolated power), but not ruling out maybe the power supply could be the issue. Will contact a local amp tech for help in diagnosing the issue. Very frustrating.

 

[tbonesullivan]

What happens when you disconnect everything and just go direct in, guitar to amp, with nothing else plugged in on that same circuit?

 

[kgbstrat]

What happens when you disconnect everything and just go direct in, guitar to amp, with nothing else plugged in on that same circuit?

It's there, but faint. As soon as soon as you add anything to chain, like the wireless or pedal board, it gets worse. I trial and error'd all different combinations - direct, wireless, different wireless, one pedal at a time, no pedals, no fx loop, etc. Very inconsistent. I rewired my pedal board and removed two pedals (one wasn't getting much use and other, a BBE Sonic Stomp now has a broken DC jack so he's on the shelf for now)

The really strange thing, and this has happened twice now, I set up for the gig and the rig was very quiet, just a hint of noise. Go to start the set, plug in again and "it's baaaaccck". No changes (on my end) other than turning the amp back on and plugging in the guitar. To minimize, I disconnected the wireless and went direct to the pedal board. Still there, but much more manageable. Still need to figure out the issue that only recently started so I can use my gear like I want. Hopefully, I can find an amp tech/electrical wiz that can help figure this out.

 

[mace]

It sure sounds like a ground issue. Check all ground/lift switches and flip them one by one to see if the issue goes away. Flip the ground switch on the back on the amp for the cab clone. It really sounds like a ground issue somewhere.

I had an issue with a DI box hooked up to the piezo out on my guitar (while using the second pick-up output to go my pedal board). I was pulling my hair out trying all different things to get rid of the hum and finally glanced upon the DI box. I flipped it's ground switch and voila, no more hum.

 

[kgbstrat]

Latest suspicion, surprisingly, is the Furman power conditioner. Just hooked up the head and just my wireless (no pedals) which is in a 2 space rack with the Furman and an IEM wireless unit. Noticed a hum that went away when I touched the antenna (basically me grounding the unit). Plugged the head and wireless units into a regular power strip and very little noise and no change when touching the antenna.

 

[kgbstrat]

It sure sounds like a ground issue. Check all ground/lift switches and flip them one by one to see if the issue goes away. Flip the ground switch on the back on the amp for the cab clone. It really sounds like a ground issue somewhere.

I had an issue with a DI box hooked up to the piezo out on my guitar (while using the second pick-up output to go my pedal board). I was pulling my hair out trying all different things to get rid of the hum and finally glanced upon the DI box. I flipped it's ground switch and voila, no more hum.

I thought the ground lift switch only affected the signal going through the cab clone. If I have an issue at this weekend's gig, I'll try this (along with a few other things). Starting to suspect my power conditioner. In a two space rack with my guitar and IEM wireless units. Swapped positions with the Furman and wireless to see if that has any impact. Noise was better without my wireless in the chain this past weekend (that has volume on the unit and selectable gain on the transmitter). Playing with those settings will be another thing to try.

 

[mace]

Yeah, you might be right. In my case the hum was from the DI box -> guitar piezo output -> guitar -> guitar pick-up ouput -> amp. I was surprised that the DI box going to the sound board affected the amp!

You reminded me, if my wireless receiver was too close to my old pedal board power supply it would hum through the amp. Same with the wah pedal being too close to the power supply. I changed power supplies (pedal power 3) and it doesn’t bother the wireless receiver.

So, yeah, in all these cases of amp hum it was caused by something “in front of” the amp. Not sure if the CC ground/lift switch would do anything. But, easy enough to check.

 

[mace]

Oh, and at some point I had to put electrical tape on the bottom edge of my wah to prevent it and the patch cable from contacting the pedal board.

You may need the opposite, maybe you have a loose ground wire in that wireless unit.

 

[kgbstrat]

Last night's result. Noise went ballistic when the sound guy connected his XLR cable to my IEM wireless unit. The IEM wireless and my guitar wireless are next to each other in a 2 space rack, using the Sennheiser mounting kit (basically connected on the bottom of each with a plate. that was absolutely the catalyst to make the noise go haywire. Going to remove the IEM unit from my rack. Assume this will resolve the major noise issue.