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Dynamic Mic Noise



 
 
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  #1  
Old August 29th 18, 01:02 PM posted to rec.audio.pro
mcp6453[_2_]
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Posts: 725
Default Dynamic Mic Noise

After 55 years in the audio business, I have encountered a strange
problem for the very first time. I set up a small mixer and two dynamic
mics for remote recording. Everything tested perfectly at home. When I
moved the setup to the remote location (an office building), there was
hum and buzz in both mics. Isolation the mics from all wall warts and
power supplies did not have an effect on the noise.

New mic cables. No change.
Different (dynamic) mics. No change.
Added dbx286s for each mic. No change.
Disconnected all external equipment from the mixer. No change.
Physically rotating the mics on the desk. Change.

At this point, I think there is a serious electrical problem in the
building. There was not much time to test, but I will be going back in
the next few days to do so. I was not able to turn off the fluorescent
lights to see if a ballast has gone nuclear.

I may take a couple of condenser mics to see if they exhibit the same
problem, but I really want to use dynamics.

Thoughts?
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  #2  
Old August 29th 18, 01:21 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,458
Default Dynamic Mic Noise

mcp6453 > wrote:
>After 55 years in the audio business, I have encountered a strange
>problem for the very first time. I set up a small mixer and two dynamic
>mics for remote recording. Everything tested perfectly at home. When I
>moved the setup to the remote location (an office building), there was
>hum and buzz in both mics. Isolation the mics from all wall warts and
>power supplies did not have an effect on the noise.
>
>New mic cables. No change.
>Different (dynamic) mics. No change.
>Added dbx286s for each mic. No change.
>Disconnected all external equipment from the mixer. No change.
>Physically rotating the mics on the desk. Change.


You have a magnetic field somewhere, maybe from a large transformer nearby,
and the microphones are picking up magnetic field leakage. Moving the
location to the other side of the room might fix everything. Then again it
might not. You might also try an original Sennheiser MD421, which has a
bucking coil to reduce magnetic pickup.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #3  
Old August 29th 18, 01:45 PM posted to rec.audio.pro
mcp6453[_2_]
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Posts: 725
Default Dynamic Mic Noise

On 8/29/2018 8:21 AM, Scott Dorsey wrote:
> mcp6453 > wrote:
>> After 55 years in the audio business, I have encountered a strange
>> problem for the very first time. I set up a small mixer and two dynamic
>> mics for remote recording. Everything tested perfectly at home. When I
>> moved the setup to the remote location (an office building), there was
>> hum and buzz in both mics. Isolation the mics from all wall warts and
>> power supplies did not have an effect on the noise.
>>
>> New mic cables. No change.
>> Different (dynamic) mics. No change.
>> Added dbx286s for each mic. No change.
>> Disconnected all external equipment from the mixer. No change.
>> Physically rotating the mics on the desk. Change.

>
> You have a magnetic field somewhere, maybe from a large transformer nearby,
> and the microphones are picking up magnetic field leakage. Moving the
> location to the other side of the room might fix everything. Then again it
> might not. You might also try an original Sennheiser MD421, which has a
> bucking coil to reduce magnetic pickup.
> --scott


Thanks, Scott. I only have one original MD421. Can you think of another
mic that would be useful to try along with the 421?
  #4  
Old August 29th 18, 01:57 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,458
Default Dynamic Mic Noise

mcp6453 > wrote:
>On 8/29/2018 8:21 AM, Scott Dorsey wrote:
>>
>> You have a magnetic field somewhere, maybe from a large transformer nearby,
>> and the microphones are picking up magnetic field leakage. Moving the
>> location to the other side of the room might fix everything. Then again it
>> might not. You might also try an original Sennheiser MD421, which has a
>> bucking coil to reduce magnetic pickup.

>
>Thanks, Scott. I only have one original MD421. Can you think of another
>mic that would be useful to try along with the 421?


Some generic condenser mike without a transformer in it.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #5  
Old August 29th 18, 02:11 PM posted to rec.audio.pro
mcp6453[_2_]
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Posts: 725
Default Dynamic Mic Noise

On 8/29/2018 8:57 AM, Scott Dorsey wrote:
> mcp6453 > wrote:
>> On 8/29/2018 8:21 AM, Scott Dorsey wrote:
>>>
>>> You have a magnetic field somewhere, maybe from a large transformer nearby,
>>> and the microphones are picking up magnetic field leakage. Moving the
>>> location to the other side of the room might fix everything. Then again it
>>> might not. You might also try an original Sennheiser MD421, which has a
>>> bucking coil to reduce magnetic pickup.

>>
>> Thanks, Scott. I only have one original MD421. Can you think of another
>> mic that would be useful to try along with the 421?

>
> Some generic condenser mike without a transformer in it.
> --scott


I'm trying to think what I might have that's transformerless. My TLM67
doesn't have a transformer, but I only have one. (We need two matching
mics for video aesthetics.) What about the Beta 87A?
  #6  
Old August 29th 18, 02:19 PM posted to rec.audio.pro
Mike Rivers[_2_]
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Posts: 1,946
Default Dynamic Mic Noise

On 8/29/2018 5:02 AM, mcp6453 wrote:
> I set up a small mixer and two dynamic mics for remote recording.
> Everything tested perfectly at home. When I moved the setup to the
> remote location (an office building), there was hum and buzz in both mics.


Look outside for a nearby cell tower. A friend had a problem like that
in his studio when Verizon turned on a new transmitter in a tower to
near his place. After verifying the cause by having a Verizon tech come
out and temporarily shut off the transmitter, he managed to get them to
leave it off. You might not be that lucky.

--
"Today's production equipment is IT based and cannot be operated without
a passing knowledge of computing, although it seems that it can be
operated without a passing knowledge of audio" - John Watkinson

Drop by http://mikeriversaudio.wordpress.com now and then
  #7  
Old August 29th 18, 06:23 PM posted to rec.audio.pro
mcp6453[_2_]
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Posts: 725
Default Dynamic Mic Noise

On 8/29/2018 9:19 AM, Mike Rivers wrote:
> On 8/29/2018 5:02 AM, mcp6453 wrote:
>> I set up a small mixer and two dynamic mics for remote recording.
>> Everything tested perfectly at home. When I moved the setup to the
>> remote location (an office building), there was hum and buzz in both
>> mics.

>
> Look outside for a nearby cell tower. A friend had a problem like that
> in his studio when Verizon turned on a new transmitter in a tower to
> near his place. After verifying the cause by having a Verizon tech come
> out and temporarily shut off the transmitter, he managed to get them to
> leave it off. You might not be that lucky.


I actually mentioned to the other guy that I thought there might be a
cell or microwave tower nearby causing the problem. I'm going to take a
few mics over there and do some experimenting. It has me ****ed off at
the moment.

Thankfully this session was not critical or time sensitive. With all of
the RF pollution going on in the country now, it's not a bad idea to
have a couple of mics in the kit that don't exhibit the problem. (one of
the mics was an SM58.)
  #8  
Old August 29th 18, 07:30 PM posted to rec.audio.pro
PStamler
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Posts: 871
Default Dynamic Mic Noise

It sound like your problem is not RFI (Radio Frequency Interference) but EMI (Electro-Magnetic Interference) Another mic with a hum-bucking coil is the Electro-Voice RE15/RE16 (same basic capsule, but the 16 has a pop filter and a slightly brighter sound). But small transformerless condensers (like Oktava MK012s) will ignore the noise too -- why exactly do you prefer to use dynamics in this situation?

Peace,
Paul Stamler
  #9  
Old August 29th 18, 07:48 PM posted to rec.audio.pro
Bill[_20_]
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Posts: 80
Default Dynamic Mic Noise

In message >, mcp6453
> writes
>After 55 years in the audio business, I have encountered a strange
>problem for the very first time. I set up a small mixer and two dynamic
>mics for remote recording. Everything tested perfectly at home. When I
>moved the setup to the remote location (an office building), there was
>hum and buzz in both mics. Isolation the mics from all wall warts and
>power supplies did not have an effect on the noise.


Some years ago, I was asked to build a small broadcast studio for a new
religious conference centre. The room they had selected looked ideal,
but during the first recce, I walked round the outside of the building
and saw that the power distribution for the whole site had its building
backing on to one wall. A subsequent test with a dynamic mic into a Uher
(remember them?) showed that hum was a real problem.

We chose a room on the other side of the site. The promotions lady was
not happy to be turned out of her nice office.
--
Bill
  #10  
Old August 29th 18, 08:21 PM posted to rec.audio.pro
mcp6453[_2_]
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Posts: 725
Default Dynamic Mic Noise

On 8/29/2018 2:30 PM, PStamler wrote:
> It sound like your problem is not RFI (Radio Frequency Interference) but EMI (Electro-Magnetic Interference) Another mic with a hum-bucking coil is the Electro-Voice RE15/RE16 (same basic capsule, but the 16 has a pop filter and a slightly brighter sound). But small transformerless condensers (like Oktava MK012s) will ignore the noise too -- why exactly do you prefer to use dynamics in this situation?
>
> Peace,
> Paul Stamler


I'll take the RE15 and RE18 to test. I don't have an RE16.

The recording is for spoken voice in a room with terrible acoustics.
Dynamic mics are more forgiving, in my experience. Having said that, I'm
going to try to Beta 87As just for fun.

 




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