The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
Tags:

Strange buzzing on Zoom F8 (can you help me identifty the problem?)
Old 9th August 2017
  #1
Here for the gear
 

Thread Starter
Strange buzzing on Zoom F8 (can you help me identifty the problem?)

Hello,
I work as an on set sound mixer/boom op and every once and a while my recorder picks up this really strange buzzing noise. I've been doing some googling and can't seem to find many other people with this problem with my specific recorder.

At first I thought it might be the lavs picking up some rogue wireless signal but it's coming through the boom track.

I run a Sennheiser MKH50 into a K-Tek pole with an internal wire into my Zoom F8 portable recorder with a standard XLR cable.

It works fine like 98% of the time but every once in a while starts picking up this buzzing noise that sounds like a fly buzzing mixed with electric current. It usually works fine if I turn it off and turn it back on but it's still frustrating that it will ruin a take occasionally and I have no idea why.

I've attached a sample of a take where it started acting up.

Any advice on how to fix or identify the problem would be fantastic.

Thanks in advance,
Louis
Attached Files

Zoom Audio Buzzing.mp3 (3.82 MB, 437 views)

Old 10th August 2017
  #2
Lives for gear
 
Matti's Avatar
Maybe I´m too old but I cannot hear anything described in the sample...

Matti
Old 10th August 2017
  #3
Here for the gear
 

Quote:
Originally Posted by polishdog90 View Post
...every once and a while my recorder picks up this really strange buzzing noise. I've been doing some googling and can't seem to find many other people with this problem with my specific recorder...

...It works fine like 98% of the time but every once in a while starts picking up this buzzing noise that sounds like a fly buzzing mixed with electric current. It usually works fine if I turn it off and turn it back on but it's still frustrating that it will ruin a take occasionally and I have no idea why...

...Any advice on how to fix or identify the problem would be fantastic...
Hi Louis,

First of all, I confirm that I hear and see the strange noise in the sample you provided.



In my opinion, the reason you hear it only some of the time is because the noise is moving in frequency (here starting at 8KHz and moving down to 3.5KHz) and as it moves through audible frequencies that's when you can hear it.
Also the noise is not constant, it is intermittent therefore it is even harder to detect all the time.

Here is a link to a video showing your noise vs. FFT display: video (74MB).

To me it looks like a drifting oscillator... but if you are going directly from a microphone to F8 then I do not know where the noise is originating from.

A simplest test you can do is this: on your F8, on that input connect pin 2 and 3 (so there is a short between these 2 pins, also turn the phantom power off) and record for few minutes. What that will do is this: Your source is 0V (no external audio), if there are any internal noises in your F8 it should get recorded.
That should give you idea if the noise is internal or external to F8.


Rob
Old 10th August 2017
  #4
Lives for gear
 

For fault finding in situation like this, every sound recordist should have one of these - a noise terminator. Standard XLR3M (metal shell) connector with a 150 ohm 1% metal film resistor connected between pin 2 and 3 (inside the shell) with pin 1 connected to the shell.

Connect it to the affected input on the recorder. Note the noise level. Remove and connect cable to input, connect terminator on other end of cable. Note noise level. Remove and connect cable to mic. Note noise. Make diagnosis.

Your problem could arise from either noise pickup on the cable (damaged shielding or funny grounding between cable and recorder or cable and mic) or the mic itself (RF condenser - spurious oscillation in the mic electronics or damaged shielding of the capsule). Substitution and/or swapping should enable more precise diagnosis.


[Note that there is a case for a second terminator unit that is identical but with the 150 ohm resistor replaced by two 75 ohm resistors in series, with a 1500 ohm resistor from their junction to pin 1. This will draw about 10mA of phantom current from the mixer/recorder, and may show where dry joints or dirty pins may generate extra noise and crackles with phantom current passing through them.]
Old 10th August 2017
  #5
Lives for gear
 
Matti's Avatar
Wasn't listening loud enough...


Matti
Old 10th August 2017
  #6
Lives for gear
 
Thomas W. Bethe's Avatar
Lots of things could be causing this, SCR Buzz, bad or partial ground on mic, incomplete ground in fish pole, or .... I had this same problem in a Fostex FR2LE recorder I never did figure out what it was. My other FR2LE worked fine. The above suggestions are all good. As is always the case in troubleshooting start from the known and work back from there. Best of Luck!
Old 10th August 2017
  #7
Lives for gear
 
Bruce Watson's Avatar
 

Quote:
Originally Posted by polishdog90 View Post
I work as an on set sound mixer/boom op and every once and a while my recorder picks up this really strange buzzing noise.
I've heard exactly this before. From my MixPre-D. I spent weeks after the fact trying to track it down. Eventually I got lucky and found it. Which probably won't help you a bit. Still...

Turned out that I forgot to pack extra batteries to a gig and had to record the last half running the MixPre-D from its AC power source. The RFI got in on the cable between the transformer (wall wart) and the MixPre-D. The sound itself was coming from the light ballasts. Installing and using fresh batteries eliminated the buzz and took me back to a black background.

That's probably not your problem, but it might point you in a reasonable direction. That being that a possible source of the noise is the on-set light ballasts. That is, HMI and fluorescents.

Also it illustrates that there are multiple paths for noise to enter the box besides the XLR inputs.
Old 11th August 2017
  #8
Here for the gear
 

Thread Starter
Thanks for the replies everybody. Somebody on another forum said that they've had that exact same problem sound with the MKH 50 and it was due to a grounding issue. I'm gonna try tightening the screws and see if that helps. If not I'll have to get a noise terminator and do some further investigation.

Last edited by polishdog90; 11th August 2017 at 02:39 AM.. Reason: clarification
Old 11th August 2017
  #9
Lives for gear
 

Sounds like RF intermod to me
Use star quad and abandon the interior cable in the KTech pole
Roger
Old 11th August 2017
  #10
Lives for gear
 
Matti's Avatar
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump