Low "rumble" in my condensor

[CPhoenix]

Help! lol..

Okay.... i've been getting a very bad low rumble type of sound in my mic recently. At first...i thought the mic went bad. I had an AKG Perception 100. I was getting some really loud low end rumblings in my recordings. It had happened overnight, with no real changes in my setup... so i figured the mic had finally gone bad. I had it for 5-6 years and didnt exactly take pristine care of it... since it was my first mic and i had it while i was inexperienced.

So... i grabbed a used AKG Perception 120. The problem seemed to go away. But now i'm noticing the rumblings again. I'm wondering if the problem isnt the mic anymore. My studio has grown a little.

I'm confident its not the preamps. I have an Audiofire4 stock pres and a Project Studios VTB. I go back n forth between mic pres n its the same rumble. So im confident its coming before the pre. I have new cables.... so i dont think its specifically the cable. I tried two different newer cables... same rumble.

Im wondering if it's either A) a grounding issue, B) two many cables and wires close to each other, or C) terrrible luck in getting a busted used mic.

Its notable that i have a significant amount of wires very close to each other. Could i be experiencing some interference? All of these wires are suuplying power to different items on my desk. I also have a power strip running into another power strip which runs into the wall socket. Could this be part of the problem? I'm ignorant when it comes to this.

I tried to do a search, but i must not have been using the right keywords here... so if anyone cuold point me to a good thread about this id really be appreciative




EDIT:::::
I forgot to mention. The hum only comes from the condensor mics. I plugged up my SM57 to the AF4 and the VTB..... no rumble whatsoever. It was dead silent.

Is the phantom power maybe getting interference?

 

[The MH]

Have you tested using another outlet or power strip yet to see what happens?

 

[The Funk Junkie]

Even though it will be a pain, you might want to move the bare minimum of your set-up into another room to see if the rumble is the same. If it's gone, then you'll know it's probably something with the room or interference with the cables or power.

 

[bandcoach]

audio sample please - hard to advise if we can't hear the rumble for ourselves....

However, it could just be a fan in your computer that is being picked up or cables knocking together due to fan or other table-borne noise - look at putting the cables inside some conduit (wrap them in a towel to begin with to see if the\at helps).....

 

[ObiK]

It kind of sounds like a ground loop. Try separating your power and audio cables. A clip would help us pinpoint the sound a bit easier though.

 

[CPhoenix]

Here's two pictures... gonna upload clips also


This is what silence is looking like for me right now. It never ever looked like this until recent.
I built an audio booth... the booth has been protecting my mic from the computer fan.

I even took my mic out of the room (since the cable is long enough)... and the level of "noise" didnt change at all. I've also covered my computer with a blanket to block the fan.... no difference. not even a nudge lower.... which makes me believe the fan isnt the culprit.


BTW... I only have the preamp gain up halfway.... and u can see how much noise is being amplified. i raised the trim of the clip so u can see what's going on better. all of that noise didnt used to be there.

 

[CPhoenix]

Here are the clips.

Its a low sound as though it may be the fan.... but its not. unless the fan is seeping into the audio cables somehow... which im not sure is possible.

The "rumble" clip is me recording silence in my booth. The "rumble1" clip is a recent recording of when i first noticed it. You can hear the low rumble.

The "Mixdown - WC Great 2" clip is a few weeks before this issue. It was with the new mic. You can hear a little bleed from the headphones... but no low rumble at all.

 

[CPhoenix]

Here's a better example''' heres a graphic of a clip that was recorded before my problem.. "norumble"

and afterwards... hes a graphic of what was recorded today "rumble3". The graphic below actually has a lot of silence in it... but u wouldn
t know that b/c so much noise is getting picked up that u can barely tell where the singer is singing.

again... i made no changes to the fan or the booth. i dont think its the computer fan

 

[CPhoenix]

The booth is double walled. 1 & 1/2 inches between the wals to break up most outside noise. (Not all... its not perfect... but a lot). I had been getting very clean,natural sounding recordings up until recently.

I'ma have work on this grounding thing n try to isolate WTF is going on

 

[~X~]

heat?????? either that or your equipment isnt gainstaged properly.

list your entire signal chain

 

[sleepy]

The track 5 clip sounds like interference from the computer, or one of your devices. I have a cheap Behringer headphone preamp and I get that sometimes. I don't get it in my recording, only through the monitoring. That might not even happen anymore. Been a while since I've heard it.


Power down your computer and monitor the sound and see if it's still there. Also, unplug any devices like cordless phones, or anything else tha transmits a signal. It might be good to invest on a power conditioner.

 

[bandcoach]

without listening I'm going for a dud cable - swap out your mic cable and try again......

 

[CPhoenix]

heat?????? either that or your equipment isnt gainstaged properly.

list your entire signal chain

Heat is possible. I did actually rearrange and you know what... I placed my AF4 on top of my Presonus HP4 headphone amp to save space. I wonder if that's part of the problem. I did notice that it seems to get worse over time.... heat gets hotter over time. Hmm.

My chain is actually extremely simple right now. I stopped using the VTB, so right now it's AKG Percep 120 > AF4 > computer.

However... in regards to sleepy's comment... i did noticed that my HP4 seems to have blown one of it's outputs. I did something extremely weird... when I turn the 3rd headphone outlet all the way up... all of the amps stop working ( amp1, 2 and 4). Weird. Maybe there's some weird sh-t going on there.


I'm going to try literally everything you guys've mentioned so far tonight. I'm so pissed and feel unprofessional w/ this hum. Hopefully i pinpoint it... it's gotta be the setup somewhere.

Here's my entire gear chain. Not much but...
Ins:
AKG 120 > AF4
SM57 > VTB > AF4
Roland JV1010 > AF4

Outs:
AF4 > Presonus HP4
AF > SM NanoPatch > MAudio BX5 monitors

Midi Out/In:
Roland JV1010

Korg TR is plugged up... i didn't run it with MIDI THRU yet.

USB stuff:
Novation SL mkii
Faderport
Korg Kaossilator Pro
ShuttlePro
Korg PadKontrol
Wireless mouse
Wireless keyboard





---------- Post added at 06:36 PM ---------- Previous post was at 06:33 PM ----------

Oh... one other thing I completely forgot to mention. This might actually help somebody troubleshoot with it.

I get a hum only from the condensor mics. Both the AKG P100 and P120. It doesn't matter if I run 'em through the AF4 preamps or the VTB. Or even the stupid Art Tube MP.

However, please note that I swapped mics and ran the SM57 > AF4 and SM57 > VTB. There was NO HUM. It was dead silent.



Is it possible for a phantom powered cable to interact w/ the voltage of these other devices? That has to be the answer somehow.

---------- Post added at 06:41 PM ---------- Previous post was at 06:36 PM ----------

It might be good to invest on a power conditioner.

Yeah... i've got this on the list... but I might have to bump up the priority now.

Any particular one a good one? I see cheap Furmans all the time. Would I be spinning my wheels getting a $50-$100 one?

 

[bandcoach]

Another thought - the phantom power supply might be shot - ripple on the line caused by dead capacitors (they are what smooth the line down to dc) could cause the sounds you are hearing.....

 

[CPhoenix]

^Man... I just tested this out also. I cut off the phantom supply on the AF4... and ran my mic back thru the VTB and only used the VTB's phantom power.... same rumble. I also flipped between cords. no change. Here's the weirdest weirdest part. I unplugged almost everything in my setup... and kept only the computer monitors, studio monitors, and the USB stuff lugged in. I just pulled out my AKG P100, plugged it to the AF4... and there is NO HUM. Its dead.... f'in silent. Like its sole purpose is to make a liar out of me. What... the hell. I went back n forth, back n forth bettween 100 and 120, and now for some odd reason the P100 is silent and the P120 is rumbling. I cant figure this out for the life of me. I'm confident the P120 is not busted... the P100 started rumbling first a few months back, which made me think it was busted and get a new mic. Now all the sudden the old mic is working perfectly and the new (used) mic is sounding busted. i need an f'in nap.

---------- Post added at 09:45 PM ---------- Previous post was at 08:07 PM ----------

Okay... i'm ready to call it on this one guys. I really really appreciate everyone's help.


I did more n more testing tonight. Nothing worked.... unplugging everything... moving things around... nothing.

I did one final test.... which leads me to believe the AKG Percep 120 I have is in fact busted, defective, and/or an ******* lol. I took my Art Tube MP. It actually has a VU meter on it, which was helpful tonight. I turned the computer off... and plugged only the ART straight into the wall socket. I did NOT route it to anything. Only the mic cable going in, nothing going out. I turned everything on the ART all the way up... gain/output/20+ db boost.... everything maxed out. Turned on the phantom power. I then plugged in the old AKG P100 mic. The needle didnt jump at all. In fact... it didnt even budge, unless i tapped the mic to make sure it was working.

Then I plugged the AKg P120 into it under the same minimal circumstances.... and the needle went crazy.

In my eyes.... it looks like there's no other way to call it, except to call this mic busted.. ad somehow the old mic I first started hearing rumblings with magically fixed from being unused for 2-3 months.

Any other possible verdicts I can come to here? I'm completely at a loss for words. Somehow my P100 is no longer busted... but its replacement is. I'm speechless.

 

[Type_1a]

^Man... I just tested this out also. I cut off the phantom supply on the AF4... and ran my mic back thru the VTB and only used the VTB's phantom power.... same rumble. I also flipped between cords. no change. Here's the weirdest weirdest part. I unplugged almost everything in my setup... and kept only the computer monitors, studio monitors, and the USB stuff lugged in. I just pulled out my AKG P100, plugged it to the AF4... and there is NO HUM. Its dead.... f'in silent. Like its sole purpose is to make a liar out of me. What... the hell. I went back n forth, back n forth bettween 100 and 120, and now for some odd reason the P100 is silent and the P120 is rumbling. I cant figure this out for the life of me. I'm confident the P120 is not busted... the P100 started rumbling first a few months back, which made me think it was busted and get a new mic. Now all the sudden the old mic is working perfectly and the new (used) mic is sounding busted. i need an f'in nap.

---------- Post added at 09:45 PM ---------- Previous post was at 08:07 PM ----------

Okay... i'm ready to call it on this one guys. I really really appreciate everyone's help.


I did more n more testing tonight. Nothing worked.... unplugging everything... moving things around... nothing.

I did one final test.... which leads me to believe the AKG Percep 120 I have is in fact busted, defective, and/or an ******* lol. I took my Art Tube MP. It actually has a VU meter on it, which was helpful tonight. I turned the computer off... and plugged only the ART straight into the wall socket. I did NOT route it to anything. Only the mic cable going in, nothing going out. I turned everything on the ART all the way up... gain/output/20+ db boost.... everything maxed out. Turned on the phantom power. I then plugged in the old AKG P100 mic. The needle didnt jump at all. In fact... it didnt even budge, unless i tapped the mic to make sure it was working.

Then I plugged the AKg P120 into it under the same minimal circumstances.... and the needle went crazy.

In my eyes.... it looks like there's no other way to call it, except to call this mic busted.. ad somehow the old mic I first started hearing rumblings with magically fixed from being unused for 2-3 months.

Any other possible verdicts I can come to here? I'm completely at a loss for words. Somehow my P100 is no longer busted... but its replacement is. I'm speechless.

dont feel too bad about this... there are famous stories of studio engineers literally ripping apart million dollar studios trying to track down a random intermittant source of noise...

ill read this again in the morning when my problem solving skills are a bit sharper.. all i can say for now is it sounds like a ground loop... since its not the cables its likely in one of the devices... one thing you can try is to insert a gaining device at various points in the signal chain and then turn the gain up and see if the noise floor increases... if it does then the noise originates before the gaining device... that will at least let you figure out where its happening...

 

[bandcoach]

Not a ground loop - as the sound does not exist with the same gear and a different mic.

So how good are your soldering skills, cphoenix????

I'm still backing a broken cable somewhere whether it is inside the mic or between any of the pieces of gear -

Open the mic up and see if the cables tying it back to the xlr have come loose or have frayed in anyway - it will look like the wire is barely hanging on - if so, resolder the cables to the xlr exactly as they are right now (if you can be certain of what goes where), otherwise find a mic mechanic to fix it for you (I'd offer, but it is a bit of a round trip to Aus and back).....

 

[CPhoenix]

^Haaaaa.... I soldered once back in my senior year of high school lol. I was actually pretty good though... so maybe I can pull it off.

I'll have to try to find a diagram on how to open this mic. I've never done it before. It seems like the top portion of the cap will twist off. I actually tried a little bit last night, but didn't wanna break it b/c I've never done it before. Guess i'll end up doing this... this is the only thing that makes sense.

I got it used for around $50 bucks... so all in all, i'm not pissed off. However... i did expect it to work for more than 2 months. Didn't get a warranty since it's cheap... nor would shipping make sense unless it were for like $20 round trip to someone. Looks like i'm stuck fixing it myself until I save up for the next level mic, which I honestly need at this stage in my career anyway to be honest. But.... it would be nice having two working condensors that are practically the same mic if i need to do any stereo recording!


Thanks bandcoach... you've inspired me to put back on my engineering hat and see if i can fix this thing lol.

In essence... a faulty cable somewhere would likely cause this rumbling sound? My guess last night was that maybe the plate inside was vibrating when its not supposed to.... or just gotten dusty, since I admittedly keep my mic uncovered in the booth, overnight. I never put it away... it just stays on the mic stand. Could it perhaps be a collection of dust as a possibility? Would dust on a mic cause this to happen? If so... i'll start locking my mics up overnight. (I told u i didn't exactly take great care of it )

 

[bandcoach]

so, I finally listened (it's been the middle of the night the last few times I've looked at this thread.)....

I've got to tell you that even with my monitors all the way up I found it hard to hear the rumble under the speakers.....

The rumble on its own, that sounds like thermal noise to me.....

Final thoughts: if the mic cable is accidentally being heated, then I would I expect this kind of noise, but I'm still banking on a slightly different cable problem.....


As for the mic, all you have to do is to remove the screw that is holding the xlr in place - then gently extract the xlr and inspect the pins and cabling.....

 

[wwallace]

Rumble noise

I know this is a super old thread but had to comment.

My new large-diaphragm condenser was producing this "ghost rumble" noise. It was independent of preamp or swapping cables and the low cut switch didn't affect it. I saw lots of references to it online but no solutions. I finally noticed that the XLR inside the mic body had pin 1 (shield) connected with a jumper to the chassis ground tab. Everything I've read states that a condenser microphone should "float" and that the shield should never ground to the mic body.

So I clipped the jumper and my B2 immediately lost the rumble, dead quiet now. Makes sense, running a jumper could create a ground loop internally ...which is why swapping out cables that had the GND connected and not, had no effect. The manufacturer probably did it to be 'universal'.