Hello there, first message on the forum and hopefully this is the right place for this kind of questions.

I have an Audio-Technica ATR2500-USB mic (), had it since release around 12 or 13 years ago, but always sounded very low so didn't use it much. Yesterday I picked it up again to see what the problem was, and found that while the volume is actually adequate (much less sensitive than other mics I have though), it picks up a hum from mains (I've recorded and confirmed it's a sine of ~50Hz) that behaves in a strange way, at least to me, so I'm hoping for at least an explanation, but even better for theories on what to do about it.

I connected the mic to my laptop and no other cables anywhere, not even the charger or anything else. I can hear the hum very faintly (noise between -60db to -55db according to Reaper). With my laptop on my lap and me sitting on a couch or a chair, if I put my feet on the floor, the noise gets noticeable louder (around -48db). If I actually touch the mic with my hands (it has an aluminum body), the noise becomes very loud and distorted (gets up to -12db), at this point it doesn't really matter if I touch the floor or not.

I'm assuming this is due to some grounding issues, but from what I've read online about people having similar problems with other kind of mics, they get better results instead of worse when touching the mic (i.e. the noise goes away). I'll try to get better pictures today, but somebody took these that might already show something to a trained eye:

Does anybody have a theory of what might be happening? I know there is probably not enough info here for a true diagnostic, but even if I cannot fix it, I'd like to know what's happening. And of course, being able to fix it will be nice, if just for the fact that I spent a lot of money at some point and will be nice to use it for something before keeping it in a closet for another 13 years :).

Thanks in advance for any tips, really appreciate it.

It does sound very much like a *lack of* grounding issue. Laptop power supplies tend to be a bit dodgy with regard to grounding in the first place, but with nothing connected you have no ground at all. If you were to ground yourself you would make the noise reduce by touching the mic, but ungrounded you're kind of a big antenna yourself.

-Scott

--
---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy" - Joe Henry

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In general, USB mics do not hum, because the connection is digital. However, it may be that there is a floating ground connection.
First, I would try another USB cable, then test the mic with another computer.

For the sake of verification, you may want to add a wire between teh mic body and the computer chassis.

If that were my mic, I would take it apart, look for damaged or poor connections, especially connections to the case, and maybe for power rail electrolytic capacitors that could have failed. But I've been doing this for over 55 years. :-)

Please try your mic on different computers and in different places to see if the hum occurs everywhere. Also, this mic apparently requires a custom driver to control its gain. Do you have that installed?

It does sound very much like a lack of grounding issue. Laptop power supplies tend to be a bit dodgy with regard to grounding in the first place, but with nothing connected you have no ground at all. If you were to ground yourself you would make the noise reduce by touching the mic, but ungrounded you're kind of a big antenna yourself.

Thanks Scott. One of the tests I did was connecting my charger, but it made the problem a bit worse, which I also didn't understand, as the charger would be grounding the laptop, but I'll try directly grounding myself and see what changes :).

In general, USB mics do not hum, because the connection is digital. However, it may be that there is a floating ground connection. First, I would try another USB cable, then test the mic with another computer.

For the sake of verification, you may want to add a wire between teh mic body and the computer chassis.

Thanks Jerry. I doubt it's the cable, it's brand new and used it with other mics with better success, but it's a good point to test that assumption. Same with testing on another computer and finally testing with a wire between both, although the USB cable should have that connection made, but of course anything can happen with cheap electronics :D.

If that were my mic, I would take it apart, look for damaged or poor connections, especially connections to the case, and maybe for power rail electrolytic capacitors that could have failed. But I've been doing this for over 55 years. :-)

Please try your mic on different computers and in different places to see if the hum occurs everywhere. Also, this mic apparently requires a custom driver to control its gain. Do you have that installed?

Thanks kennjava, I'd definitely take it apart and check, but I obviously don't have the experience to know what to look for (although I dabble in Arduinos and things like that), but I can definitely post some photos and maybe you or somebody else can point where there might be a potential fault. About that driver you mention, do you have any links about that? I haven't found anything on the manual or any search regarding "drivers" anywhere on the official site.

Again, thank you all for your time.

Ok, so just as a bit of an update, as I was getting ready to disassemble it I decided to make a few more tests. I connected it, and suddenly got no noise (after getting noise for hours yesterday). I thought it was because now I'm in my office instead of another random place of the house, but when I touched the cable, the noise came back. Long story short, it seems the connector is faulty. I can twist it a few times and sometimes the noise disappears, not even in the exact same spot, it's just random. I can also make it disappear if I manually connect the connector shielding with the USB shield (just tried putting one of my keys in the connector :D), so yeah, there is maybe a cracked solder joint or something similar inside, I'll have to open and deal with it.

Thanks again to everybody offering suggestions, really appreciate it.

On Tue, Jul 9, 2024 at 07:38 AM, Edu Garcia wrote:

About that driver you mention, do you have any links about that?

The driver is mentioned in the 3rd paragraph of your link:

... it does not say "custom", and you're right, the manual only refers to a default driver. Have you accessed the driver to make level adjustments, as described in the manual? Try plugging headphones directly into the mic, to see what that's like.

, if you haven't already seen it.

... Have you accessed the driver to make level adjustments, as described in the manual? Try plugging headphones directly into the mic, to see what that's like.

Here's a review, with some tips about application, if you haven't already seen it.

Thanks, I remember reading that review a while ago, it rings a bell, but I checked it again just in case. And plugging headphones directly doesn't seem to have any noise, but I think it's just because either mic gain is too low, or my headphone's impedance is too high (or low, still learning about all of this :D), or both. Also, level adjustments on the "driver" (Windows side of things, basically) doesn't seem to change anything, Reaper doesn't seem to notice what I change there (only input level and format available).

Anyway, after "fixing" the issue (I'm not completely sure it's fixed, I still hear the hum although it seems to be lower) the new noise for the mic is -67db, which I'm not sure if it's expected, good, bad or what... I feel there is more that can be done to reduce that hum even more, but -67db is much better than -50db :)

. . . I still hear the hum although it seems to be lower) . . .
_________________________________________________________

Notwithstanding my rookie status, considering the fact the hum comes and goes jockeying the connectors ... I sorta, kinda, almost, maybe, possibly suspect what is termed the "Pin 1" problem, which you can read about here: Jim Brown K9YC is an AES guy with loads of funky ideas, some of which may be correct:




Also maybe see info and links to articles here:






I have found this sort of issue pop up in all sorts of situations, especially wiring microphones to amateur radio transceivers, sometimes requiring the cable shield to be linked to the connector case and, also therefore, equipmenent chassis, and sometimes not, it is a mixed bag - working in some cases, other times making it worse - but I figure it may be related ... or not ... remember I AM still a rookie!

Just thinking aloud out of turn ... James K8JHR

I was going to add - solder a jumper between pin 1 and the shield on the XLR to ensure the preamp casing and the cable shield are continuous.

I have has to do this several times where a mic will sound great when plugged into my recorder running on batteries, but buzzes like hell when you plug the power supply in.

Jack

Le 10/07/2024 à 14:58, Richards a écrit?:

possibly suspect what is termed the "Pin 1" problem, which you can read about here:

Actually, the Pin 1 problem is a different issue, which happens only when interconnecting pieces of equipment that are grounded on remote points.
A microphone, in essence, is floating; its only connection to ground is via its cable.

Thank you all for the additional ideas, and sorry for the delay, I don't seem to be receiving updates through email for some reason, will have to check settings.

Notwithstanding my rookie status, considering the fact the hum comes and goes jockeying the connectors ... I sorta, kinda, almost, maybe, possibly suspect what is termed the "Pin 1" problem, which you can read about here: Jim Brown K9YC is an AES guy with loads of funky ideas, some of which may be correct:

Will check those links, thanks! Although this mic is an USB one and not XLR, so not sure it applies, or not in the same explicit way?

I was going to add - solder a jumper between pin 1 and the shield on the XLR to ensure the preamp casing and the cable shield are continuous.

Thanks, although as mentioned above this is an USB mic, if the problem is the preamp I won't even know where to start looking for that :D.