[mcp6453[_2_]]

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?

[Scott Dorsey]

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."

[mcp6453[_2_]]

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?

[Scott Dorsey]

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."

[mcp6453[_2_]]

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?

[Phil Allison[_4_]]

mcp6453 wrote:




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?



** Condenser mics normally use Mu-Metal shielded transformers OR are transformerless. In both cases nearby magnetic hum fields have little or no effect.

Dynamic mics pick up nearby hum fields via their **voice coils** - examples like the SM57 & SM58 have an unshielded transformer buried in the handle as well that also picks up induced hum.

Few mics have hum bucking coils fitted, suggesting that most users regard it as a non problem and simply move the mic away from the hum source.


..... Phil


so without a hum bucking coil to defeat the effect are all excellent hum det

[geoff]

On 30/08/2018 12:45 AM, mcp6453 wrote:
On 8/29/2018 8:21 AM, Scott Dorsey wrote:
mcp6453Â* 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.Â* Moving the
location to the other side of the room might fix everything.Â* Then
again it
might not.Â* 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?

Just the one would indicate if a local strong hum field was the problem,
or not .

geoff

[Mike Rivers[_2_]]

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

[mcp6453[_2_]]

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.)

[PStamler]

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

[mcp6453[_2_]]

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.

[mcp6453[_2_]]

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


By the way, I agree that it's probably EMI instead of RFI. Now if I can
just find my roll of mu-metal tape, I'll wrap the bodies of the mics.
Or, maybe I can turn the room into a Faraday cage.

[Adrian Tuddenham[_2_]]

mcp6453 wrote:

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


By the way, I agree that it's probably EMI instead of RFI. Now if I can
just find my roll of mu-metal tape, I'll wrap the bodies of the mics.
Or, maybe I can turn the room into a Faraday cage.

Use the mic as a sensor and track down the source.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[mcp6453[_2_]]

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?

Here's what I've found. The problem is definitely EMI. There's a cell
phone tower less than a block away. Moving the mic in the room can
exacerbate or eliminate the noise. Unfortunately there is not a
practical position that will eliminate it. So, I took an RE15, RE18,
MD421U, and Beta 87A. All of the mics eliminated the noise although
there was still a little with the 421. Since the 87As were the only ones
I had two of, I used those. They didn't sound so good for this
application and need to be replaced.

Upon further research, I discovered that the PR40 (my favorite
spoken-word mic) and the RE20/27 have humbucking coils. With God as my
witness (ala WKRP), after all this time, I never knew about the coils.
How I overlooked it escapes me. What this experience has taught me is
that it is a REALLY good idea to use mics with humbucking coils whenever
possible - particularly in unfamiliar territory. Since I almost always
use a PR40, I've avoided the problem in most cases. However, the PR40 is
very large for on-camera use, so I'm thinking about a couple of RE16s,
unless someone can suggest less expensive alternatives that also include
effective humbucking coils.

[John Williamson]

On 06/09/2018 17:36, mcp6453 wrote:
Here's what I've found. The problem is definitely EMI. There's a cell
phone tower less than a block away. Moving the mic in the room can
exacerbate or eliminate the noise. Unfortunately there is not a
practical position that will eliminate it. So, I took an RE15, RE18,
MD421U, and Beta 87A. All of the mics eliminated the noise although
there was still a little with the 421. Since the 87As were the only ones
I had two of, I used those. They didn't sound so good for this
application and need to be replaced.

If the interference is from a cell tower a block away, then it is RFI,
and can probably be stopped dead by putting ferrite beads on the mic
cables near the mic and mixer (If used). Cell interference has a
characteristic sound, and is not a hum.

EMI is much shorter range, will be a constant or intermittent hum or
buzz, and will likely be from a transformer or light fitting choke
you've not found yet. Moving the mic will show where the field is
strongest, and lead you to what needs to be turned off. Changing the
angle of the mic may help with this, as the sensitivity depends on the
relative angles of the mic and the field, though changing the mic angle
will also foul up the recording...


--
Tciao for Now!

John.

[Mike Rivers[_2_]]

On 9/6/2018 1:02 PM, John Williamson wrote:
If the interference is from a cell tower a block away, then it is RF

RFI is a special case of EMI. They're both electromagnetic radiation.
What you get from a power line or a wall wart is interference from
electromagnetic induction.

Picky, picky.

A friend of mine with this problem actually got Verizon to turn off the
transmitter on the tower that was causing the interference with his
mics, but it took a lot of complaining. Something that might help (he
got the transmitter turned off before he placed the order) is to change
out the connectors on a few mic cables with the Neutric EMI-filtered ones.

http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc



--

For a good time, call http://mikeriversaudio.wordpress.com

[mcp6453[_2_]]

On 9/6/2018 2:23 PM, Mike Rivers wrote:
On 9/6/2018 1:02 PM, John Williamson wrote:
If the interference is from a cell tower a block away, then it is RF

RFI is a special case of EMI. They're both electromagnetic radiation.
What you get from a power line or a wall wart is interference from
electromagnetic induction.

Picky, picky.

A friend of mine with this problem actually got Verizon to turn off the
transmitter on the tower that was causing the interference with his
mics, but it took a lot of complaining. Something that might help (he
got the transmitter turned off before he placed the order) is to change
out the connectors on a few mic cables with the Neutric EMI-filtered ones.

http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc

These connectors appear to be a good idea for high-frequency
interference. It would be interesting to try them. If I were on the road
a lot, I'd probably use cables with them all the time.

[John Williamson]

On 06/09/2018 19:23, Mike Rivers wrote:
On 9/6/2018 1:02 PM, John Williamson wrote:
If the interference is from a cell tower a block away, then it is RF

RFI is a special case of EMI. They're both electromagnetic radiation.
What you get from a power line or a wall wart is interference from
electromagnetic induction.

Picky, picky.

Not really. What I call EMI is usually low frequency, directly induced
in the coils, while RFI is a modulated higher frequency, which normally
only affects circuits with a semiconductor or other rectifying component
in them, such as a preamp.

I find it a useful distinction to draw, as the cures are different.

The OP describes a hum or a buzz, rather than the typical "chirping"
sound of a cellphone being picked up, so I was guessing at LF, possibly
from a choke, fluorescent light or (Unlikely) a SMPS near the
microphone, which doesn't have a humbucking coil. It's hard to get
interference from cellphone transmissions, even from base stations,
more than a few feet from the microphone due to the low power and
inverse square law of propagation, though an experienced movie sound guy
can often tell what make of cellphone is about to ring on set.....


--
Tciao for Now!

John.

[Ty Ford[_2_]]

On Thursday, September 6, 2018 at 1:02:58 PM UTC-4, John Williamson wrote:
On 06/09/2018 17:36, mcp6453 wrote:
Here's what I've found. The problem is definitely EMI. There's a cell
phone tower less than a block away. Moving the mic in the room can
exacerbate or eliminate the noise. Unfortunately there is not a
practical position that will eliminate it. So, I took an RE15, RE18,
MD421U, and Beta 87A. All of the mics eliminated the noise although
there was still a little with the 421. Since the 87As were the only ones
I had two of, I used those. They didn't sound so good for this
application and need to be replaced.

If the interference is from a cell tower a block away, then it is RFI,
and can probably be stopped dead by putting ferrite beads on the mic
cables near the mic and mixer (If used). Cell interference has a
characteristic sound, and is not a hum.

EMI is much shorter range, will be a constant or intermittent hum or
buzz, and will likely be from a transformer or light fitting choke
you've not found yet. Moving the mic will show where the field is
strongest, and lead you to what needs to be turned off. Changing the
angle of the mic may help with this, as the sensitivity depends on the
relative angles of the mic and the field, though changing the mic angle
will also foul up the recording...


--
Tciao for Now!

John.

I'm with John on this one. 3 million years ago when I got my first DAW (AKG DSE7000) I set it up only to find that the CRT was blowing a ring of noise right at my 421. I moved on to a Gefell M71.

Wow looks like a newsgroup post from what 20 years ago?

Regards,

Ty Ford

[Scott Dorsey]

Ty Ford wrote:
I'm with John on this one. 3 million years ago when I got my first DAW (AKG DSE7000) I set it up only to find that the CRT was blowing a ring of noise right at my 421. I moved on to a Gefell M71.

This also is direct magnetic interference. CRTs are awful for this... big
coils operating at 30 Hz and 17 KHz, spewing magnetic fields all over the
place. They couple into microphones.

And, as noted, the 421 is specifically designed to deal with magnetic fields
using a bucking coil, so if the 421 is picking it up, you've got a big one!

The good thing about direct magnetic interference is that, as Mike noticed,
it's directional. Turn the microphone until it's parallel to the field and
the noise goes away. Secondly, as you should notice if you have ever played
with permanent magnets on the fridge, the field drops off very quickly with
distance.

I am thinking the cell tower is a red herring and that what you've got here
is a magnetic field.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison[_4_]]

mcp6453 wrote:


Here's what I've found. The problem is definitely EMI. There's a cell
phone tower less than a block away.


** Well out of range then.


Moving the mic in the room can
exacerbate or eliminate the noise. Unfortunately there is not a
practical position that will eliminate it.


** So it's not the cell tower.


So, I took an RE15, RE18,
MD421U, and Beta 87A. All of the mics eliminated the noise although
there was still a little with the 421.


** The RE15, RE18 and MD421 all have hum bucking coils, while the 87a is a condenser mic.



Upon further research, I discovered that the PR40 (my favorite
spoken-word mic) and the RE20/27 have humbucking coils. With God as my
witness (ala WKRP), after all this time, I never knew about the coils.
How I overlooked it escapes me.


** The others escaped you too.


What this experience has taught me is
that it is a REALLY good idea to use mics with humbucking coils whenever
possible - particularly in unfamiliar territory. Since I almost always
use a PR40, I've avoided the problem in most cases. However, the PR40 is
very large for on-camera use, so I'm thinking about a couple of RE16s,
unless someone can suggest less expensive alternatives that also include
effective humbucking coils.


** Condenser mics do not need such coils.

There is a big hum field in or near that office room you have yet to uncover.



..... Phil

[Bill[_20_]]

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

[PStamler]

On Wednesday, August 29, 2018 at 7:02:13 AM

An electric guitar with a single-coil pickup makes a great probe for electromagnetic hum.

And dynamic mics are no more immune to acoustically bad rooms than condenser mics.

Peace,
Paul

[geoff]

On 30/08/2018 4:31 PM, PStamler wrote:
On Wednesday, August 29, 2018 at 7:02:13 AM

An electric guitar with a single-coil pickup makes a great probe for electromagnetic hum.

And dynamic mics are no more immune to acoustically bad rooms than condenser mics.

Peace,
Paul



I guess a condenser mic may be more sensitive and pick up more of the
low-level rubbish from the room that a dynamic may miss ...

geoff

[John Williamson]

On 30/08/2018 09:21, geoff wrote:

I guess a condenser mic may be more sensitive and pick up more of the
low-level rubbish from the room that a dynamic may miss ...

Not so much if it's hum originating from the magnetic field a
transformer or lighting choke gives out, unless it uses a transformer in
the circuit somewhere.

Condenser mics tend to be more sensitive to things like cellphones or
two way radios, which are not a steady hum as described. They may, if
it's really close, pick up the discharge in a fluorescent tube.


--
Tciao for Now!

John.

[geoff]

On 30/08/2018 10:57 PM, John Williamson wrote:
On 30/08/2018 09:21, geoff wrote:

I guess a condenser mic may be more sensitive and pick up more of the
low-level rubbish from the room that a dynamic may miss ...

Not so much if it's hum originating from the magnetic field a
transformer or lighting choke gives out, unless it uses a transformer in
the circuit somewhere.

Condenser mics tend to be more sensitive to things like cellphones or
two way radios, which are not a steady hum as described. They may, if
it's really close, pick up the discharge in a fluorescent tube.




Yeah, but was referring to the apparent preference for using dynamics in
the first place in that nasty room environment, apart from the hum thing.

geoff

[PStamler]

Meanwhile I notice that the OP says he needs to use two microphones for visual purposes. Will both of those mics be live? If so, and if the capsules are apart, he may run into problems with comb filtering.

[PStamler]

The Beta58 is alive and well, now called the Beta 58A. Swee****er, among others, sells them:

https://www.swee****er.com/store/det...cal-microphone

In my one experience eith a Beta 58A, it sounded better than any SM58 I'd heard. The fact that Tom Russell was singing into it didn't hurt.

Peace,
Paul

[Phil Allison[_4_]]

PStamler wrote:



The Beta58 is alive and well, now called the Beta 58A.


** Not true.

The Beta58 was Shure's first attempt to modernise & upgrade the venerable SM58.

Among several other changes, the Beta58 featured a hum bucking coil and eliminated the transformer in the handle by using a higher impedance diaphragm coil - 250ohm instead of circa 13ohm, which allowed direct output.

It remained on sale for a short time in the early 1990s, before being withdrawn and replaced with the Beta58A in which the hum bucking coil was removed but strangely the transformer returned along with a circa 20ohm diaphragm.



..... Phil