Amp crackling noise

[Markdude]

I have a Marshall JCM900 SL-X 2100 head and it makes a crackling noise when it is turned off of standby. The noise is most frequent right after the amp is turned on (and standby is turned off) and then gradually diminishes a bit but never seems to completely go away. The noise is similar to the sound of scratchy pots being turned, but sometimes I can hear kind of a "swooshing" or surging noise too. This noise occurs whether or not something is plugged into the input jack, and it stays at the same level regardless of the master volume setting. Here's a video of the noise:

I had the amp looked over by a reputable tech and he said he could find nothing wrong with it. He cleaned all the jacks and pots, said he "tightened up" some components, and tested all of the tubes, and he was never able to replicate the noise, even though it happens every single time I turn the amp on in my house. When I picked the amp up from him today, it indeed was dead quiet when plugged in at his shop.

I've tried many outlets in my house and tried turning other lights/electronic devices off and unplugging them. I've also tried swapping the preamp tubes with brand new ones (even though the tech tested the preamp tubes and power tubes) but that didn't help either. It seems plausible that maybe the house's wiring is the problem. I have noticed some quirks, like how in one of the bedrooms, I can hear a crackling sound from the wall while I'm flipping the light switch (the sound happens as the switch is in between the on and off position), and the other day I plugged a brand new Playstation 4 power supply into a surge protector in the living room and I heard a pop and the lights flickered for a fraction of a second (but no components or lights failed).

I've owned 2 other amps while living in this house and one of them did seem to have an excessive hum, but the other one seemed fine.

Does anyone have any insight about what might be causing this and how it can be resolved? Would a voltage regulator, power conditioner, isolation transformer, etc. do any good? Unfortunately the house is a rental so I would probably only be able to get wiring changes done if the wiring was truly dangerous and/or out of code.

 

[glip22]

I would still think it's the amp and not your house. Did the tech try different tubes? If not, he sucks. That is step one. I don't care that they test good. Not when it comes to noise. It sounds like a cold solder joint to me. When the area warms up a little it subsides.
Did you try to use another outlet on a different breaker in your house just to be sure?
I would then open the amp and poke around with a chopstick to see if I could find the area or cause.
Reflow connections on the boards.

 

[LP Freak]

Sounds tube related. Probably a preamp. Get a new set and swap them out one by one.

 

[psychodave]

Do you have wifi in your house? Are you using any type of booster that uses the house wiring as an antenna? May sound funny, but sometimes you guitar cord will act as an antenna and pick some unwanted sounds. It's just good for thought.

 

[Racerxrated]

Do you have wifi in your house? Are you using any type of booster that uses the house wiring as an antenna? May sound funny, but sometimes you guitar cord will act as an antenna and pick some unwanted sounds. It's just good for thought.

I have this same thing happen at home, only during spring/summer. Intermittent, and the only cure seems to be unplugging and moving to a different outlet. Doesn't make sense but there it is.

 

[Markdude]

It's definitely not a preamp tube -- I've tried swapping the preamp tubes with those from an amp that works fine (both one by one and all at the same time) and a brand new set of preamp tubes with 72-hour burn in from Valve Queen. I've also tried removing preamp tubes on by one and even removing all of the preamp tubes and powering up the amp and it makes the exact same noise. I know it could be the sockets themselves but the tech cleaned them and I believe he checked the solder joints. I haven't tried any other power tubes but the fact that it makes this noise every single time I turn it on at my house (which has been probably 40+ times now) but was dead quiet when we turned it on at the tech's shop (I heard it in person myself and played my own guitar through it, so I know he's not lying) makes me think it's something more complicated than just tubes.

Not sure if it matters but if I leave standby on for long enough and then turn standby back off (without power the amp all the way down between), it reacts in the same way (lots of crackles at first, then they gradually diminish but don't completely go away).

The tech told me he cleaned the tube sockets and checked the solder joints, but I'm not against asking him to do it again (or going to another one) if it really seems like the power in my house can't possibly be the problem.

I've also tried turning off all computers in the house and unplugging the modem and router, but no change. I've tried 4 outlets in different rooms in my house but it makes the noises everywhere. I'm not sure if it would be considered any kind of booster but I do have boxes that send the cable modem's signal through the house's cable wiring, but the amp still does this with those boxes unplugged. I also don't think it's guitar cable related -- it does this even with nothing plugged into the input jack (and as I mentioned above, it does it even with no preamp tubes in the amp).

This is driving me crazy! It's a great sounding amp but I hate the crackling. I guess my next step will be to take it to a friend's house and see how it reacts there, since I've only heard it with two power sources so far.

 

[LP Freak]

Your last statement was going to be my suggestion. Take it to a buddies house and see what happens.

 

[MrDowntown]

I may have missed this somewhere, but has it always done it? Either way, To me that sounds like electrical interference (of some kind). If it made that noise and the nothing was plugged into the amp; guitar, pedals,etc (only amp plugged to wall receptacle and head to cab), you may want to try a different power cord if removable type, and and different cable for your cab.

If this isn't replicated at a different house, I'd say it's definitively something to do with; house wiring, fluorescent lighting, maybe a scanner or router running Nearby. If you have a PC running nearby with big fans running in it..that'll cause interference also.

Just my .02. GL

 

[scottosan]

My bet is on the power tubes. Remove the phase inverter so that no signal gets to the power section. If it still happens, it's the power tubes. If it's only when they first turn on, this has happened to me many times and always has been power tubes. They may still test well, as the crackle is mechanical/structural and has nothing to do with the output parameters.

 

[Markdude]

I've only had the amp for 3 months or so, but it's always done that in the period I've owned it. I've tried different speaker cables and power cables. Haven't tried different cabs yet other than at the tech's shop where it was quiet, but when I try it at my friend's place I'll try some other cabs too.

I'm not against getting some new power tubes, but if they're the culprit, I'm wondering why I didn't hear the noise at the tech's shop.

 

[Metal1977]

My bet is on the power tubes. Remove the phase inverter so that no signal gets to the power section. If it still happens, it's the power tubes. If it's only when they first turn on, this has happened to me many times and always has been power tubes. They may still test well, as the crackle is mechanical/structural and has nothing to do with the output parameters.

Yup! From my experience crackling or popping noise almost always come from power tubes. Very easy to trouble shoot. Try to gently tap on the power tubes while your amp is on, by doing this you will find which one is the culprit. Preamp tubes are more related to feedback or hiss problems.

Chris

 

[scottosan]

I'm gonna go out on a limb and predict they are JJs too. Very common.

 

[Markdude]

Turns out it is the power tubes!

At the time I dropped the amp off at the tech, I had no other amps with EL34s and figured I'd rather pay the bench fee than buy new power amp tubes in case something more complicated was wrong. While waiting on the tech, I snagged a Hughes & Kettner Statesman Dual EL34 because I'd always wanted to try one. Like I mentioned before, the fact that it didn't make the noise at the tech's shop really made me think that tubes weren't the issue (and that fact still confuses me), but I decided to put the Marshall in half power mode and put the H&K's power tubes in the inner slots on the Marshall. Voila, works perfectly now.

And scottosan, you were right, they are JJ power tubes.

 

[MrDowntown]

And the tech told you tubes were ok?

 

[Markdude]

Yeah, but I don't disbelieve him. We fired the amp up in his shop and there was no crackling at all, I heard it myself. I still have no idea what the deal is with that but I'm glad I finally figured out the issue.

 

[MrDowntown]

Yea that's crazy, and proves I know less than Shit about amps!

Glad you got it figured out...some knowledgeable dudes here

 

[scottosan]

And scottosan, you were right, they are JJ power tubes.

At one point, I owned at least 7 amps, all EL34 based. I used to be a huge JJ fan until about 4 years ago and ran into constant issues with JJ's regardless of the vendor. I noticed the higher the plate voltage the more issues I had. My preference for reliability in any amp is the Ruby EL34BHT. They will take anything you through at them and are great for the price. They are made specifically for hight plate voltage amp, like Bogners and some Marshalls.

 

[Adambomb]

My bet is on the power tubes. Remove the phase inverter so that no signal gets to the power section. If it still happens, it's the power tubes. If it's only when they first turn on, this has happened to me many times and always has been power tubes. They may still test well, as the crackle is mechanical/structural and has nothing to do with the output parameters.

Thats my bet too. Do exactly what he said. Remove PI preamp tube like he said above. Im almost certain its a power tube "tubes". Good luck

Whoops.. glad you got fixed OP. Had a Friedman did the same thing but not all the time and it was a faulty power tube. Good deal, carry on Sir.

 

[glip22]

Turns out it is the power tubes!

At the time I dropped the amp off at the tech, I had no other amps with EL34s and figured I'd rather pay the bench fee than buy new power amp tubes in case something more complicated was wrong. While waiting on the tech, I snagged a Hughes & Kettner Statesman Dual EL34 because I'd always wanted to try one. Like I mentioned before, the fact that it didn't make the noise at the tech's shop really made me think that tubes weren't the issue (and that fact still confuses me), but I decided to put the Marshall in half power mode and put the H&K's power tubes in the inner slots on the Marshall. Voila, works perfectly now.

And scottosan, you were right, they are JJ power tubes.

I hope you learned a good lesson. 90% of noises, etc. with amps turn out to be tubes. Always change all tubes and even the fuses first before costing all the poor forum members hours of their expensive time and effort JK.
Glad it's fixed and find a new tech. A tech that simply tests your existing tubes sucks. Yeah, I know it didn't do it at his place but he should have replaced them anyway.