Please help me debug noise when plugging in small bass amp.
August 21, 2021 8:50 AM   Subscribe

1) I recently bought a Joyo MA-10B portable bass amp. Sounds great for practicing on my passive Squier PB+J when I power the amp with batteries, however:

2) When I plug it in using the provided 1.2A adapter, and crank the volume and/or gain past 50% or 60%, a LOT of noise comes out of it, not just humming but crackling.

3) The noise subsides if I touch any metallic part of the bass, or the strings and especially the cable.

4) There is no noise when using batteries, maybe a distant whine if I turn everything up to 100%.

5) This also happens if I plug in a Telecaster.

6) I checked the grounding of the outlet I'm using with a multi-meter: plugged in the red end to the power-hole, the black to the neutral, reads 210V (Chile is nominally 220V). Plugged in the black end to ground, reads 210V as well.

7) The Joyo adapter only has 2 prongs, so I think the grounding is irrelevant?

8) Tried 3 different guitar cables, including a brand new one.

9) I also get some noise when playing bass or guitar on an Orange Crush 20 guitar amp, and in this case it depends on the angle of the instrument to the amp (parallel to amp: more noise, perpendicular: less). This noise is not as bad as on the Joyo, but I never turn the Orange up past 20% volume, so maybe it's related to that.
posted by signal to Technology (6 answers total) 2 users marked this as a favorite
 
3) The noise subsides if I touch any metallic part of the bass, or the strings and especially the cable.
...
7) The Joyo adapter only has 2 prongs, so I think the grounding is irrelevant?


Not an expert, but it seems you have two different 'grounds' in your system (resolved by touching a metal part and grounding through yourself), and that's never good. Maybe this bloke can help?
posted by pompomtom at 9:10 AM on August 21, 2021


The adapter you are using for powering the amp clearly has a bit of a 50Hz coupling between the mains and the DC side. You could solve this by running a wire from the mains socket ground prong to a metal part on the amp or one of the wires on the output side of the adapter. Either wire should work, but the 0V/negative wire is the preferred one.
posted by Stoneshop at 9:37 AM on August 21, 2021


3) The noise subsides if I touch any metallic part of the bass, or the strings and especially the cable

Check that you have a string ground wire between the bridge and the rest of the guitar electronics.

You may want/need to add shielding to the bass.

Check that all solder connections in the bass electronics are good.

6) I checked the grounding of the outlet I'm using with a multi-meter: plugged in the red end to the power-hole, the black to the neutral, reads 210V (Chile is nominally 220V). Plugged in the black end to ground, reads 210V as well.

I'm not versed in the Chile electrical system, but this is unclear to me - is your wall outlet 2-hole or 3-hole?

7) The Joyo adapter only has 2 prongs, so I think the grounding is irrelevant?

The fact that you get no noise when using batteries suggests that grounding is relevant - the question is where the problem lies and what you can do about it.

The thing is, there's a ground in the electrical system eventually. On 2-prong outlets there's usually a ground connected to the neutral side of the supply somewhere up the line, like in the circuit breaker/fuse panel box for your house.

I can't find any specific info online, but you should check if the JOYO adaptor is the "self-regulating" kind where it can use either 110 or 220/240. Most are these days, but it's possible you got the wrong one or their adapters just don't do that.

It's also possible that the Joyo adapter is not great, doesn't have much in the way of voltage regulation & noise filtering in it, and getting a better quality adapter (like a True Tone OneSpot) will help.

I also get some noise when playing bass or guitar on an Orange Crush 20 guitar amp, and in this case it depends on the angle of the instrument to the amp (parallel to amp: more noise, perpendicular: less)

Single coil guitar pickup. (Which is what your Tele has and the "J" pickup in your Squier PJ is.) They've just inherently got a level of noise - the fact that the noise changes as you change your physical position is the tell. Not a whole lot you can do about that.

If you have any fluorescent lights (or neon) in the room, turn 'em off. They generate noise that gets easily picked up by single coils.

This noise is not as bad as on the Joyo, but I never turn the Orange up past 20% volume, so maybe it's related to that.

Probably, to at least some extent. There's a whole thing about gain structure - which knobs are you turning up how much - that I don't really have time to get into at the moment, but you should start your noise investigations with the guitar/bass volumes all the way up, which will give you the best signal-to-noise ratio as your starting point.
posted by soundguy99 at 10:24 AM on August 21, 2021 [4 favorites]


First off, eponysterical.

Crackling makes me think something is arcing, and the fact that this happens only when you use your 1.2 A adapter makes me think it could be the transformer inside that. However, the fact that the noise disappears when you touch anything metallic on the bass makes me think that you're changing the overall capacitance of something in the circuit by touching it and helping to decouple your amp from an external source of noise. If I were you, I'd try the following:

1) See if the noise is location-dependent, that is, does it go away or change if you use the amp in a different room. If so it might be that your amp is picking up noise from an external source, and needs better shielding and/or some extra capacitance on the power supply.

2) See if the noise is present using a different 1.2 A adapter. If not, it was probably a bad transformer in that adapter, problem solved.
posted by biogeo at 11:15 AM on August 21, 2021


Response by poster: Thanks for all the answers!

soundguy99: " I'm not versed in the Chile electrical system, but this is unclear to me - is your wall outlet 2-hole or 3-hole? "

3 hole.
posted by signal at 1:39 PM on August 21, 2021


Best answer: " I'm not versed in the Chile electrical system, but this is unclear to me - is your wall outlet 2-hole or 3-hole? "

3 hole.


OK, so I think your wall power is fine (or good enough).

I'm kinda increasingly thinking the power adapter is broken or just not very good in the first place.

One other possibility is if the amp power adapter is the US kind with 2 flat blades, then you would need another adapter to convert from that to the round hole jacks for Chile. Maybe that converter is bad? Try another one if you have it.

crank the volume and/or gain past 50% or 60%

The thing is, on amps, "gain" and "volume" are not the same thing. They do both increase the signal level, but not in the same place in the circuit, and they have different purposes. So this could be relevant to your noise concerns.

(Apologies if this seems a little condescendingly basic - I know you've posted stuff to Music & I know you've commented on other music FPP's & Asks, but, uh, you wouldn't be the first musician I know who makes stuff without really knowing how it works . . .)

"Gain" is essentially the first level control, which boosts the signal from your instrument into the preamp stage of the circuit. For a lot of amps (especially guitar amps) this is where they can add varying amounts of intentional distortion. Exactly how this works depends on the amp, but the short version is that it adds LOTS of signal boost and overloads some of the components in the preamp circuit.

So not only is distortion inherently noisy, but because it's a big signal boost right at the beginning, it can emphasize or increase other existing noise issues - like a crackling from a bad guitar cable will be minor if the gain is low, but when you crank up the gain it's HOLY COW SNAP CRACKLE POP.

"Volume" controls are essentially the last volume right before the signal goes out to the speaker - IOW, it controls how loud your amp is.

ANYWAY, so the Joyo 10B has a "Drive" channel and a "Normal" channel. So if you're on the "Drive" channel there's already some level of distortion added, and how much distortion is controlled by the "Gain" knob. It's a bit unclear from the manual if the "Gain" knob does anything if you'e switched to the "Normal" channel, but there's a good chance it does.

So your cleanest sound for the amp would be 1) turn your bass guitar volume(s) up all the way 2) Make sure you're switched to the "Normal" channel of the amp 3) turn the "Volume" control on the amp up all the way - no wait, actually, turn it up halfway to start until you figure out if the "gain" control does anything 4) start with the "gain" control all the way down 5) start to pluck a string while slowly turning the "gain" control up.

If the gain control does something - or if you have no sound out of the amp with the gain control all the way down - then you want to turn the gain knob up until you hear some distortion, then back it down so you're not getting that first boost of overdrive. Then adjust "Volume" for how loud you want the amp to actually be.

IOW, once you're sure you've gotten the cleanest signal you can from the amp, you know that you're not adding noise or distortion from your amp settings, so whatever noise issues you have are something else - shielding, bad power adapter, etc.

The Orange seems to be pretty similar, although I would note that AFAICT this is a slightly different circuit, where the "Gain" and "Volume" only apply to the "Dirty" channel - the "clean" channel only has the "Clean channel volume" control. I suspect, because the manual notes that "higher settings on the clean channel will produce natural overdrive and breakup", that this is also technically a "gain" control, and Orange is just bypassing a second "volume" control.

But so yeah, basically same situation as the Joyo - if you're in the "Dirty" channel you're already adding some noise & increasing the chances you're boosting other noise, and if you're in the "clean" channel there's only so far you can turn it up before you start to overdrive some portion of the circuit and add noise from the amp and/or boost other noise.
posted by soundguy99 at 4:33 PM on August 23, 2021 [3 favorites]


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