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Mystery amp buzz driving me crazy..

R

Rama777

Jul 19, 2022
56
34
#1
So I’ve got a pretty new Ampeg Rocket 210. I wanted to record something today for the first time with the amp and was having trouble getting a buzzing noise which I noticed on playback. It turns out it’s coming from the speaker. I never noticed it before. You kind of have to put your ear right in line with the speaker and be pretty close. I wouldn’t have noticed it otherwise.

Turning knobs does nothing. It is a constant low buzz that is effected by absolutely nothing other than being powered on.

I tried every circuit in the house. Same result. I cut off every other breaker in the house and that didn’t do anything.

my other Ampeg cab does not buzz.

I noticed something else. Of course if I move the microphone off axis, it diminishes but is still present and essentially the recorded buzz quality just changes. But here’s where I feel like it gets weird, if I hold the microphone near the sides of the amp, and especially up close to the head of the amp, it buzzes really bad in the microphone. I tried holding the mic close to my other amp to make sure that wasn’t just a thing with amps. Sure enough no proximity buzzing noise from the other amp.

No way I can record with this amp. I don’t want to hastily call Ampeg if it’s possibly some other interference or ground issue. Any ideas??
 
#2
What mic are you using, and is it an XLR balanced connection?

If so, the pin 1 shield connection must carry through to the housing of the mic otherwise it will be noisy yet still pass audio.

I have seen inexpensive and counterfeit Chinese mics with such defects. Pin 1 and the capsule shield are not carried through to the housing.

Also, some mics are more prone to this noise, try another mic that's known to be genuine, there are a ton of counterfeits out there.
 
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#4
I tried the DI out for the first time. Horrible buzz. Ground lift switch does nothing. It’s definitely not the cable. Or at least I don’t think it is because the cable sounds clean using it on any other piece of gear.
 
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#7
I've got the same amp.
It may not have anything to do with your issue, but I went over mine with a screwdriver and tightened all the screws when I got it. So many were surprisingly loose.
It may not help, but if something is loose I wonder if it could cause some buzzing?
 
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#10
I listened to the buzz/hiss on the recording from the microphone and the DI both and the noise is definitely different. Both "buzzy hisses" but using an EQ sweep, the frequencies of the noise is in different places.
 
#13
Ampeg support is unhelpful. I’ve ruled out grounding issues. Technically I haven’t “ruled out” voltage fluctuations on my mains supply, but I am very doubtful that’s the issue.

to reiterate, microphones pick up a very intense electromagnetic signal from hovering a microphone around the sides of the cabinet and near the amp portion of the unit itself. The amp itself is clearly putting off an EMI signal.

furthermore, I hovered the microphone over an outlet and got the expected sound of 60hz interference. I switched on the power on my amp while still holding the microphone at the outlet and all the sudden it causes the outlet EMI signal to get much much louder, matching the sound of the amp EMI signal I was getting from hovering the mic over the amp. If I switch on the power on my other amp while holding the mic near the outlet, the steady 60hz signal remains unchanged. So without a doubt the amp has some kind of wiring or shielding issue. The amp itself is not only creating interference within its own field but also adding a ton of noise on the circuit.

Any electronics pros know where I should look in the amp for the potential sources of the problem?
 
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#14
Your mic / cabling / or preamp sounds to be the real problem. Any balanced, properly shielded microphone shouldn't pickup any noise near an AC outlet, unless it's passing lots of current, and even then, it should be only marginally noisier in real close proximity to the outlet. It sounds more like an electrostatic shielding issue.
 
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#15
Interesting. I kind of doubt it’s the microphones because I’ve tried an SM57, a sennheiser 441 and a Telefunken CU-29 vacuum tube mic all with the same results. I’ve tried 5 different xlr cables, but admittedly they are all pretty old but have been generally well taken care of.

The preamps I suppose could be the culprit. I have two preamps on my 1200 dollar audio interface. They sound totally clean on everything besides the amp. I can record on my other amp with zero EMI issues.

As for the outlet noise, yes, it’s only when I hold a microphone right up to an outlet. A rather faint 60hz buzz unless I turn my amp on, which increases the volume of the buzz at the outlet maybe by 4-800%.

Again the amp cabinet itself also puts off a tremendous buzz with a microphone in proximity, whereas my other amp does no such thing.

Also the DI is fiendishly noisy, which helps rule out microphone issues. Oh and snap!! I forgot to mention that the headphone jack on the amp also puts out the same identical buzz sound, which kind of seals the deal and proves to me that it’s the amp correct?
 
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#16
It shouldn’t buzz. Compare your amp to YouTube demo videos. Forget about the mic, do you hear it when you are playing?

If no, look at your mic, cable, and interface. Are they near fluorescent lights or LED dimmers, a router, or other power supplies, even a computer monitor can be a problem. Try to keep them away from any potential offending device. Are the cables short and snaked back and forth on the floor. Is the mic cable microphonic. Slam it onto the floor and see if it picks up noise.

Try positioning the mic a couple of feet from the speaker.
 
#17
Just edited my last post. Added the fact that the headphone jack makes the exact same noise so it has nothing to do with the microphones or cables. My headphones sound clean on every other source all on the same outlet.
 
#18
I appreciate everyone’s sound input!! I really feel like the headphone jack closes the case on it being the amp, unless there is still any potential issue with the power, but I can say for certain that nothing changes by using a 3-prong to 2-prong adapter, presumably ruling out a grounding issue so far as I understand.
 
#19
Rama777 said:
I appreciate everyone’s sound input!! I really feel like the headphone jack closes the case on it being the amp, unless there is still any potential issue with the power, but I can say for certain that nothing changes by using a 3-prong to 2-prong adapter, presumably ruling out a grounding issue so far as I understand.
Click to expand...

Sounds like you’ve done all you can on your own.
 

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