Humming / Buzzing Noise - Audio Setup - AC - Microphone - Apollo Twin X - Neumann TLM 103 - Furman

[RTX7030R]

What the noise sounds like:

https://imgur.com/a/nf6K2JH

I have a humming sound which is more or less audible depending on how much I increase the input gain / headphone output - it is also however - perpetually present, as it is visible digitally within software (such as an EQ) - the problem is something to do with either the microphone, or an electrical issue because I have eliminated the other possibilities via trial and error (it is not my computer because the noise is present while the computer is not connected to the interface/ I have used alternative interfaces / I have used alternative XLR Cables / It is not an issue with headphones as the noise is still present without the use of headphones). This noise only happens when phantom power on the Apollo is activated - This noise only happens when there is both ends of an XLR cable plugged in at both the microphone and interface entry points, if either is unplugged the noise stops. After speaking to many people, I was recommended to purchase a power conditioner as the issue may be dirty ac which is creating interference and noise. So I bought a power conditioner, plugged my interface into it, and powered it on, the noise still persists.

Does anybody, anybody at all have a possible solution to resolve this issue? I have been trying for so, long, countless hours sat looking through forums and videos, speaking which people over the phone, nothing I have tried has solved this bane of mine. On a side note, when I touch the XLR cable at the point where it plugs into the microphone, the volume of the sound decreased ever so slightly.

Apollo Twin X
Neumann TLM 103
Furman M-10 X E Power Conditioner

 

[sam_adams]

This noise only happens when phantom power on the Apollo is activated

Assuming that you have this device powered from an AC adapter, contact Apollo tech support and see if they have any suggestions. There is probably a boost regulator for the 48V phantom power inside that might be bad.

 

[RTX7030R]

Assuming that you have this device powered from an AC adapter, contact Apollo tech support and see if they have any suggestions. There is probably a boost regulator for the 48V phantom power inside that might be bad.

Thank you for that, I appreciate the response greatly! I did this very thing months ago, the Apollo representative told me to return the interface, which I did, the humming still happens on my current Apollo (I bought another one) and also happens on my M-Audio 2X2, so i’m still pretty confused!

 

[AnalogSteph]

After speaking to many people, I was recommended to purchase a power conditioner as the issue may be dirty ac which is creating interference and noise.

Infuriating. Other people's money always is the easiest to spend.

As it happens, I have seen this type of problem before. Assuming the hum is not actually picked up acoustically - it is a microphone after all - the most likely explanation is that the microphone's electrostatic shielding is less than perfect for some reason. Condenser microphones need an extremely high-impedance input to work well, higher than you'll see in anything in anything else - you'll literally be finding biasing resistors of up to 10 gigaohms in there. Their capsules and wiring are extremely sensitive when it comes to electrostatic coupling (after all, they are supposed to pick up tiny changes in capacitance), so their case and basket must form a rather effective Faraday cage as an extension of the XLR cable shield. If some part is left with poor contact, you will be picking up mains hum, even when the computer attached to the audio interface is grounded via its mains power supply (though the less its ground potential agrees with its surroundings, the worse it will be).

Is this a used or new TLM103? If the former, I would not rule out that it may have been improperly reassembled at some point. If either the hot or cold signal wire have come undone from the XLR connector, that would probably do it as well.

This sort of issue is rather common in the type of Chinese-built mics which have a metal tube kind of wedged between the basket support and a screw-on ring (very common on budget condensers, my t.bone SC400 just being one of many). If the ring is not cinched down properly, the tube covering the electronics may lose good contact and hence shielding effectiveness, with the result of hum being picked up. I imagine a Neumann would have a slightly more refined construction than this honestly rather crude affair.

Look what I came across while looking for disassembly instructions:

Maybe your problem is much the same as that guy had. (It goes without saying that a certain level of confidence and experience with repairs is much advised before tackling a job like this.)

I wonder why mics don't seem to be using the kind of contact fingers that used to be so common on PC cases... perhaps those don't work well with very round shapes as opposed to flat panels.

 

[thecheapseats]

with a DMM - check continuity from the mic's ouput pin1 to the lower shell case of the mic (don't scratch it).... from your vid (no audio?) looks like shield is disconnected as the peak is 50/60 hz - ish... the vid posted above is helpful... just for a reality check - can you borrow another p48 mic and see if that is ok?...