[Truth]

I have a ribbon microphone that is picking up AM radio. I had no idea
what it was until today. It's usually a squeal and I don't hear the
voice or music. So I was guessing and trying different things all to
no avail. I was turning off equipment, moving it far away from the
mics, removing any fluorescent lights, etc. Problem remained. I even
got some special power cords for the mic power supplies. Still, the
squeal is there.

But today, in addition to the squeal like you're getting a bad radio
signal, I could hear the radio content as well which made it clear
what the problem was. I turned on the radio downstairs and tuned it
to AM. I found the station the mic was picking up in my recording and
it was the same type of squeal, so it seems this is the problem. The
problem is not constant, it comes and goes. I've tried the mic with
different preamps and I get the same problem with both. I've also
tried different microphones. Only the ribbon mic picks up this RMI
squeal.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power? Is this problem due to
noisy power lines and will getting a power conditioner eliminate it do
you think? I had my equipment in the same room as the mic. I moved
it out of the room and into the hall to test and the problem remains.
Replaced all fluorescent bulbs with regular incandescent ones. There
is a dimmer in the house, but it's located down the hall and far away
and is turned off. Nothing is powered on in the same room as the mic
now and the squeal is still there. I've turned off all radios in the
house as well. Unplugged a wireless router. None of this helps,
which makes me think it's the power.

[Paul Stamler]

Does the interference change when you move the mic cable around?

Peace,
Paul

[Truth]

On Sep 13, 3:03 am, "Paul Stamler" wrote:
Does the interference change when you move the mic cable around?

Peace,
Paul

Thanks for all your replies and help, I appreciate it. I haven't
tried that yet while the problem is occurring. I will do that and see
what happens next time. Up to this point, I have left the cable in
the same spot unmoved. Sometimes I hear absolutely no squeal/whistle
and at other times the noise is unbearable, all the while I have not
touched the cables.

[Scott Dorsey]

Truth wrote:

Thanks for all your replies and help, I appreciate it. I haven't
tried that yet while the problem is occurring. I will do that and see
what happens next time. Up to this point, I have left the cable in
the same spot unmoved. Sometimes I hear absolutely no squeal/whistle
and at other times the noise is unbearable, all the while I have not
touched the cables.

What model microphone, preamp, and cable are we talking about here?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Truth]

On Sep 13, 11:52 am, (Scott Dorsey) wrote:
Truth wrote:

Thanks for all your replies and help, I appreciate it. I haven't
tried that yet while the problem is occurring. I will do that and see
what happens next time. Up to this point, I have left the cable in
the same spot unmoved. Sometimes I hear absolutely no squeal/whistle
and at other times the noise is unbearable, all the while I have not
touched the cables.

What model microphone, preamp, and cable are we talking about here?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

My chain:

House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI
Lynx Two C Sound Card

[Eeyore]

Truth wrote:

"Paul Stamler" wrote:
Does the interference change when you move the mic cable around?

Thanks for all your replies and help, I appreciate it. I haven't
tried that yet while the problem is occurring. I will do that and see
what happens next time. Up to this point, I have left the cable in
the same spot unmoved. Sometimes I hear absolutely no squeal/whistle
and at other times the noise is unbearable, all the while I have not
touched the cables.

Something that I don't think we've yet touched on is that there may be some
instability (oscillation) at very high frequencies in your equipment and it's
mixing with the RF. That could cause a 'scream'.

Graham

[Richard Crowley]

"Eeyore" wrote ...
Something that I don't think we've yet touched on is that there may be
some
instability (oscillation) at very high frequencies in your equipment and
it's
mixing with the RF. That could cause a 'scream'.

If he hears the same "squeal" in an independent radio receiver,
it could be an indication of something wierd happening in his RF
neighborhood. His audio recording equipment could be operating
"nominally" and we are barking up the wrong tree.

[Arny Krueger]

"Richard Crowley" wrote in message
...
"Eeyore" wrote ...
Something that I don't think we've yet touched on is that there may be
some
instability (oscillation) at very high frequencies in your equipment and
it's
mixing with the RF. That could cause a 'scream'.

If he hears the same "squeal" in an independent radio receiver,
it could be an indication of something wierd happening in his RF
neighborhood. His audio recording equipment could be operating
"nominally" and we are barking up the wrong tree.

In many urban areas, AM receivers simply find assorted squeals. Especially
true if there is a powerful transmitter nearby.

[William Sommerwerck]

I'm coming in late, so sorry if I repeat something some else already said.

If the mic is on a stand, try coiling the cable around the stand. I learned
this about 25 years ago, when experiencing RFI at a concert. Coiling the
cable can introduce enough inductance to "choke" the RF.

[Truth]

On Sep 13, 1:27 pm, "William Sommerwerck"
wrote:
I'm coming in late, so sorry if I repeat something some else already said.

If the mic is on a stand, try coiling the cable around the stand. I learned
this about 25 years ago, when experiencing RFI at a concert. Coiling the
cable can introduce enough inductance to "choke" the RF.

Thanks very much for that tip, I will give that a try if the problem
comes back. Right now, I'm not hearing it.

[Truth]

On Sep 13, 3:03 am, "Paul Stamler" wrote:
Does the interference change when you move the mic cable around?

Peace,
Paul

Now that the cable is more or less in a straight path, unwound, I have
been moving it around and it doesn't introduce squeal. One key
difference is that it's unwound rather than in a heap overlapping
itself.

[David Morgan \(MAMS\)]

"Truth" wrote in message oups.com...
On Sep 13, 3:03 am, "Paul Stamler" wrote:
Does the interference change when you move the mic cable around?

Peace,
Paul

Now that the cable is more or less in a straight path, unwound, I have
been moving it around and it doesn't introduce squeal. One key
difference is that it's unwound rather than in a heap overlapping
itself.


What about the RF....(?) That is usually a cabling (signal issue).

[Arny Krueger]

"David Morgan (MAMS)" /Odm wrote in message
newsnYGi.563$io2.18@trnddc06...

"Truth" wrote in message
oups.com...
On Sep 13, 3:03 am, "Paul Stamler" wrote:
Does the interference change when you move the mic cable around?

Peace,
Paul

Now that the cable is more or less in a straight path, unwound, I have
been moving it around and it doesn't introduce squeal. One key
difference is that it's unwound rather than in a heap overlapping
itself.


What about the RF....(?) That is usually a cabling (signal issue).

I suspect that arranging the cable in a linear form may have slightly
increased its series inductance, and/or decreased its mutual inductance with
circularly-polarized sources.

[David Morgan \(MAMS\)]

"Arny Krueger" wrote in message . ..

"David Morgan (MAMS)" /Odm wrote in message
newsnYGi.563$io2.18@trnddc06...

"Truth" wrote in message
oups.com...
On Sep 13, 3:03 am, "Paul Stamler" wrote:
Does the interference change when you move the mic cable around?

Peace,
Paul

Now that the cable is more or less in a straight path, unwound, I have
been moving it around and it doesn't introduce squeal. One key
difference is that it's unwound rather than in a heap overlapping
itself.


What about the RF....(?) That is usually a cabling (signal issue).

I suspect that arranging the cable in a linear form may have slightly
increased its series inductance, and/or decreased its mutual inductance with
circularly-polarized sources.


I think thats called a coil.

[Truth]

On Sep 16, 8:11 am, "Arny Krueger" wrote:
"David Morgan (MAMS)" /Odm wrote in messagenewsnYGi.563$io2.18@trnddc06...





"Truth" wrote in message
roups.com...
On Sep 13, 3:03 am, "Paul Stamler" wrote:
Does the interference change when you move the mic cable around?

Peace,
Paul

Now that the cable is more or less in a straight path, unwound, I have
been moving it around and it doesn't introduce squeal. One key
difference is that it's unwound rather than in a heap overlapping
itself.

What about the RF....(?) That is usually a cabling (signal issue).

I suspect that arranging the cable in a linear form may have slightly
increased its series inductance, and/or decreased its mutual inductance with
circularly-polarized sources.



Yes, the position of the 7 pin cables is now linear which has caused
the squeal to disappear for the time being. Before they were in a
random heap
overlaying themselves on the wooden floor of the tracking room. Now
they are in a straight path out the tracking room into the hall that
is covered with carpet. So they are on some carpet, which may have
some effect on them, I don't know. Perhaps something similar to the
ferrite bead effect. Or more likely what you described.

If the cables are to blame, perhaps the different frequencies being
picked up are due to the arrangement of the cables on the floor. I
know it's a far shot, but does this make any sense to any of you
experts?

[Eeyore]

Truth wrote:

I have a ribbon microphone that is picking up AM radio.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power?

I think you mean "I'm just wondering what is demodulating the interference" and
the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if
it's there, the trick is not to demodulate it.

What's the mic ?

What's your preamp / mixer / interface ?

Graham

[Truth]

On Sep 13, 7:15 am, Eeyore
wrote:
Truth wrote:
I have a ribbon microphone that is picking up AM radio.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power?

I think you mean "I'm just wondering what is demodulating the interference" and
the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if
it's there, the trick is not to demodulate it.

What's the mic ?

What's your preamp / mixer / interface ?

Graham

Interesting. Could the problem perhaps originate in the power, get
transferred and made worse on the way to the computer?

My chain:

House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI
Lynx Two C Sound Card

[Eeyore]

Truth wrote:

Eeyore wrote:
Truth wrote:
I have a ribbon microphone that is picking up AM radio.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power?

I think you mean "I'm just wondering what is demodulating the interference" and
the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if
it's there, the trick is not to demodulate it.

What's the mic ?

What's your preamp / mixer / interface ?

Graham

Interesting. Could the problem perhaps originate in the power, get
transferred and made worse on the way to the computer?

Not really.


My chain:

House Power
Ribbon Mic's Power Box

Ribbon Mics don't need extermal power. Oh I see. It seems your Royers have some
strange 'head amplifier'.

I wouln't mind betting there's your problem.


Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)

What do you mean by non-standard ? Alarm bells are ringing already.


2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI

A DH Labs DI ? I can't find anything by googling. Is it active or passive ?

Graham

[Truth]

On Sep 13, 12:20 pm, Eeyore
wrote:
Truth wrote:
Eeyore wrote:
Truth wrote:
I have a ribbon microphone that is picking up AM radio.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power?

I think you mean "I'm just wondering what is demodulating the interference" and
the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if
it's there, the trick is not to demodulate it.

What's the mic ?

What's your preamp / mixer / interface ?

Graham

Interesting. Could the problem perhaps originate in the power, get
transferred and made worse on the way to the computer?

Not really.

My chain:

House Power
Ribbon Mic's Power Box

Ribbon Mics don't need extermal power. Oh I see. It seems your Royers have some
strange 'head amplifier'.

I wouln't mind betting there's your problem.

Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)

What do you mean by non-standard ? Alarm bells are ringing already.

2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI

A DH Labs DI ? I can't find anything by googling. Is it active or passive ?

Graham

Sorry, that wasn't clear. DH labs 12 feet 110 Ohm XLR used as the
connection between the preamps and the sound card. Two used for an
analog connection between the Pendulum and the Lynx Two C, one used
for the connection between the Weiss ADC2 Digital Output to the sound
card's digital input.

[Eeyore]

Truth wrote:

Eeyore wrote:

A DH Labs DI ? I can't find anything by googling. Is it active or passive ?


Sorry, that wasn't clear. DH labs 12 feet 110 Ohm XLR used as the
connection between the preamps and the sound card.

What the heck is a "DH labs 12 feet 110 Ohm XLR".

Are you using daft audiophool 'snake oil' cables ?

I'd get rid of those straight away and use something sensible and reliable.

Graham

[Truth]

On Sep 13, 12:20 pm, Eeyore
wrote:
Truth wrote:
Eeyore wrote:
Truth wrote:
I have a ribbon microphone that is picking up AM radio.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power?

I think you mean "I'm just wondering what is demodulating the interference" and
the answer is almost certainly the mic preamp. Any cable will 'pick up' RF if
it's there, the trick is not to demodulate it.

What's the mic ?

What's your preamp / mixer / interface ?

Graham

Interesting. Could the problem perhaps originate in the power, get
transferred and made worse on the way to the computer?

Not really.

My chain:

House Power
Ribbon Mic's Power Box

Ribbon Mics don't need extermal power. Oh I see. It seems your Royers have some
strange 'head amplifier'.

I wouln't mind betting there's your problem.

Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)

What do you mean by non-standard ? Alarm bells are ringing already.

2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI

A DH Labs DI ? I can't find anything by googling. Is it active or passive ?

Graham

The cable connecting the ribbon mic to it's dedicated power supply is
a 7 pin cable provided by Royer Labs. Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

[Arny Krueger]

"Truth" wrote in message
oups.com...

Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

The mic's power supply is supposed to provide resistance to RF, and probably
does. AFAIK, Royer are nobody's fools.

RF usually doesn't come in on the power lines, nearly as often as it simply
comes through the air.

Power line circuitry tends to attenuate RF - as anybody who has tried to run
an X-10 system knows.

[Scott Dorsey]

Truth wrote:
The cable connecting the ribbon mic to it's dedicated power supply is
a 7 pin cable provided by Royer Labs. Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

If it's an RF problem, it has nothing to do with the power system.

I'm not so sure it _is_ an RF problem, though.

When you heard this squealing sound on an AM radio tuned to 790, was
your audio gear operating at the time?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Paul Stamler]

"Truth" wrote in message
oups.com...

The cable connecting the ribbon mic to it's dedicated power supply is
a 7 pin cable provided by Royer Labs. Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

Much more likely in the mic itself. The transformer in the power supply is
usually pretty good at filtering out RF on the line.

Peace,
Paul

[Eeyore]

Truth wrote:

The cable connecting the ribbon mic to it's dedicated power supply is
a 7 pin cable provided by Royer Labs. Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

Anyone's guess. For the life of me I don't understand why you'r fixating over the idea
that the AC power is the problem. It's aboutt he leat likely thing ever ! Are you
susceptible to the kind of audiophool nonsense that gave us the Tice Clock and the Shakti
Stone and one way cables ? Hint, the guys selling that stuff are fraudsters and they talk
nothing but garbage. You need to erase everything from your mind that you ever heard in
the 'hi-fi' mags.

So, is the 3 pin XLR mic output on the 'power supply' ? I've looked for the info but
haven't found anything useful.

Graham

[Scott Dorsey]

Truth wrote:
House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics

OKAY! So you don't have normal ribbon microphones at all. You have
the 122V.

So, the first question: Do you hear the problem with the 122V turned off?
If turning off the mike stops the noise, the rectification is taking place
inside the mike.

The second question: If you connect up only a single microphone, do you
hear it?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Truth]

On Sep 13, 1:28 pm, (Scott Dorsey) wrote:
Truth wrote:
House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics

OKAY! So you don't have normal ribbon microphones at all. You have
the 122V.

So, the first question: Do you hear the problem with the 122V turned off?
If turning off the mike stops the noise, the rectification is taking place
inside the mike.

The second question: If you connect up only a single microphone, do you
hear it?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Yes, turning off the mic stops the noise from what I remember. That
still leaves the power box, or 7 pin cables connecting the box to the
mic as possible sources if you disregard the power itself. Well, the
source in my opinion is the radio station but there is little I can do
about that. After moving the power boxes out in the hall and
unwinding the 7 pin cables out so they are more or less straight and
not a in pile, the problem has seemed to disappear. It's too early to
say though. Every time I think I got rid of it, it comes back
eventually. This makes me think the cable is the problem and I would
benefit from a shorter run. It's something I will mention to Royer
when I contact them. I'm monitoring using the Pendulum preamp as I
type this, all is good right now.

I notice it with both microphones, sometimes at the same time,
sometimes at different times, whether they are both powered or not.
If I turn off one I still hear it in the other.

[Arny Krueger]

"Truth" wrote in message
ups.com...

I have a ribbon microphone that is picking up AM radio.

I don't think so. What you have is a mic that is picking up RF and a mic
preamp or something else that is demodulating the RF and presenting the
modulation of the RF as audio.

I had no idea
what it was until today. It's usually a squeal and I don't hear the
voice or music. So I was guessing and trying different things all to
no avail. I was turning off equipment, moving it far away from the
mics, removing any fluorescent lights, etc. Problem remained. I even
got some special power cords for the mic power supplies. Still, the
squeal is there.

The squeal might be a hetrodyne between two different RF sources. Hetrodynes
are due to nonlinearity. The nonlinearity is probably due to some active
component being driven outside its linear range.

But today, in addition to the squeal like you're getting a bad radio
signal, I could hear the radio content as well which made it clear
what the problem was. I turned on the radio downstairs and tuned it
to AM. I found the station the mic was picking up in my recording and
it was the same type of squeal, so it seems this is the problem.

Seems consistent with the other things that you've said so far.

The problem is not constant, it comes and goes.

Moving mics and cables around can cause these sorts of changes.

I've tried the mic with
different preamps and I get the same problem with both.

Either the two preamps share the same sensitivity to RF, or the problem is
elsewhere.

I've also
tried different microphones. Only the ribbon mic picks up this RMI
squeal.

One major variable is that ribbon mics usually demand that a lot more gain
be used to amplify them.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power?

A corroded connection in the mic itself could be providing the necessary
nonlinearity.

Or, your mic preamps might be doing just fine all by themselves, but are
outputting too much RF for some downstream component to handle linearly.

Is this problem due to
noisy power lines and will getting a power conditioner eliminate it do
you think?

No. I suspect that your mic cables are acting like antennas.

I had my equipment in the same room as the mic. I moved
it out of the room and into the hall to test and the problem remains.
Replaced all fluorescent bulbs with regular incandescent ones. There
is a dimmer in the house, but it's located down the hall and far away
and is turned off.

Dimmer noise is generally overlaid with the power line frequency. So, its
more like a buzz than a squeal or a radio station program.

Nothing is powered on in the same room as the mic
now and the squeal is still there. I've turned off all radios in the
house as well. Unplugged a wireless router. None of this helps,
which makes me think it's the power.

The RF is most likely in the space in and around your house.

Something as simple as a low value ceramic capacitor across the mics
terminals could make a difference.

I've found that mic preamps vary tremendously in how well-equipped they are
to reject RF. Some have multiple-section LC filters (good) and some have
nothing in particular or maybe just a capacitor across the input terminals
(not so good).

I think that the best mic preamp I have in terms of RF rejection is my SX
202. Frankly, for whatever reason, I've mostly used the SX 202 in my remote
recording sessions, some of which have been in the high-RF parts of my city.
I don't know how many problems I've never experienced because of my choice
of equipment.

I don't use ribbon mics at all, so I don't know what would happen with a
more difficult microphone than the common kinds of condensor mics that I
prefer.

[Eeyore]

Arny Krueger wrote:

I've found that mic preamps vary tremendously in how well-equipped they are
to reject RF. Some have multiple-section LC filters (good) and some have
nothing in particular or maybe just a capacitor across the input terminals
(not so good).

And different designs vary hugely as to their susceptibilty too.

Very few 'consumer' or pro-sumer mic pre designs employ much in the way of any
series L (inductance) at the front end.

Graham

[AndyP[_2_]]

Arny Krueger wrote:

[cut]
I've found that mic preamps vary tremendously in how well-equipped they
are
to reject RF. Some have multiple-section LC filters (good) and some have
nothing in particular or maybe just a capacitor across the input terminals
(not so good).

[cut]

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Andy

[Eeyore]

AndyP wrote:

Arny Krueger wrote:

I've found that mic preamps vary tremendously in how well-equipped they
are to reject RF. Some have multiple-section LC filters (good) and some have

nothing in particular or maybe just a capacitor across the input terminals
(not so good).

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Generally it does. I expect incompetent product design could perhaps mess that
up too but transformer inputs do indeed normally perform very well in this
respect.

Graham

[Scott Dorsey]

In article , AndyP wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always. There are some poorly-designed transformer inputs out
there too, though.

What kind of preamp, microphone, and cable are we dealing with here?
And what makes you think it's AM?
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Eeyore]

Scott Dorsey wrote:

AndyP wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always. There are some poorly-designed transformer inputs out
there too, though.

What kind of preamp, microphone, and cable are we dealing with here?
And what makes you think it's AM?

He said it was an AM station.

AM is also readily demodulated by any diode-like behaviour.

Graham

[Scott Dorsey]

Eeyore wrote:
Scott Dorsey wrote:

AndyP wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always. There are some poorly-designed transformer inputs out
there too, though.

What kind of preamp, microphone, and cable are we dealing with here?
And what makes you think it's AM?

He said it was an AM station.

Right, but he said he was hearing a whistle.

AM is also readily demodulated by any diode-like behaviour.

Yes, but then you hear voices.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Truth]

On Sep 13, 11:17 am, (Scott Dorsey) wrote:
In article , AndyP wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always. There are some poorly-designed transformer inputs out
there too, though.

What kind of preamp, microphone, and cable are we dealing with here?
And what makes you think it's AM?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

My chain:

House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI
Lynx Two C Sound Card

[[email protected]]

On Sep 13, 9:18 am, Truth wrote:
On Sep 13, 11:17 am, (Scott Dorsey) wrote:

In article , AndyP wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always. There are some poorly-designed transformer inputs out
there too, though.

What kind of preamp, microphone, and cable are we dealing with here?
And what makes you think it's AM?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

My chain:

House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI
Lynx Two C Sound Card

This is in response to the individual who is experiencing interference
with a Royer R-122V ribbon microphone. I just found out about your
problem and want to inform you that the issue is likely due to a
defective vacuum tube. Not any of the other things that you may have
been trying in an effort to cure the problem. The oscillation that
occur randomly (between 6.5K-8.5K) are the result of mechanical design
changes in the 5840 tube. Certain date coded tubes exhibit this
phenomenon. It's a problem that is easily fixed, even if the mic had
been sent in previously for service and still exhibited the problem.
The actual source of the problem was not discovered until fairly
recently. Please contact Royer Labs and speak to Rick Perrotta for a
technical explanation and an arangemnet to get the mics replaced or
repaired at no charge. Our number is (818) 847-0121

[Mike Rivers]

On Sep 13, 9:34 am, "AndyP" wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always.

But we haven't established yet that Truth has an RFI problem, or if
RFI is hs only problem. The radio station is definitely suspicious but
the description of the noise as a squeal that's sometimes unbearable
suggests feedback.

All of his gear is good quality stuff so I'm suspecting either cockpit
trouble or something broken. I wonder what he hears when he
substitutes a different mic for the Royer, or better yet, substitutes
a "dummy mic" - an XLR plug with a 150 ohm resistor connected between
pins 2 and 3.

[Truth]

On Sep 13, 7:48 am, "Arny Krueger" wrote:
"Truth" wrote in message

ups.com...

I have a ribbon microphone that is picking up AM radio.

I don't think so. What you have is a mic that is picking up RF and a mic
preamp or something else that is demodulating the RF and presenting the
modulation of the RF as audio.

I had no idea
what it was until today. It's usually a squeal and I don't hear the
voice or music. So I was guessing and trying different things all to
no avail. I was turning off equipment, moving it far away from the
mics, removing any fluorescent lights, etc. Problem remained. I even
got some special power cords for the mic power supplies. Still, the
squeal is there.

The squeal might be a hetrodyne between two different RF sources. Hetrodynes
are due to nonlinearity. The nonlinearity is probably due to some active
component being driven outside its linear range.

But today, in addition to the squeal like you're getting a bad radio
signal, I could hear the radio content as well which made it clear
what the problem was. I turned on the radio downstairs and tuned it
to AM. I found the station the mic was picking up in my recording and
it was the same type of squeal, so it seems this is the problem.

Seems consistent with the other things that you've said so far.

The problem is not constant, it comes and goes.

Moving mics and cables around can cause these sorts of changes.

I've tried the mic with
different preamps and I get the same problem with both.

Either the two preamps share the same sensitivity to RF, or the problem is
elsewhere.

I've also
tried different microphones. Only the ribbon mic picks up this RMI
squeal.

One major variable is that ribbon mics usually demand that a lot more gain
be used to amplify them.

Now I'm just wondering what is picking up the interference, is it the
mic itself, the mic cables, or the main power?

A corroded connection in the mic itself could be providing the necessary
nonlinearity.

Or, your mic preamps might be doing just fine all by themselves, but are
outputting too much RF for some downstream component to handle linearly.

Is this problem due to
noisy power lines and will getting a power conditioner eliminate it do
you think?

No. I suspect that your mic cables are acting like antennas.

I had my equipment in the same room as the mic. I moved
it out of the room and into the hall to test and the problem remains.
Replaced all fluorescent bulbs with regular incandescent ones. There
is a dimmer in the house, but it's located down the hall and far away
and is turned off.

Dimmer noise is generally overlaid with the power line frequency. So, its
more like a buzz than a squeal or a radio station program.

Nothing is powered on in the same room as the mic
now and the squeal is still there. I've turned off all radios in the
house as well. Unplugged a wireless router. None of this helps,
which makes me think it's the power.

The RF is most likely in the space in and around your house.

Something as simple as a low value ceramic capacitor across the mics
terminals could make a difference.

I've found that mic preamps vary tremendously in how well-equipped they are
to reject RF. Some have multiple-section LC filters (good) and some have
nothing in particular or maybe just a capacitor across the input terminals
(not so good).

I think that the best mic preamp I have in terms of RF rejection is my SX
202. Frankly, for whatever reason, I've mostly used the SX 202 in my remote
recording sessions, some of which have been in the high-RF parts of my city.
I don't know how many problems I've never experienced because of my choice
of equipment.

I don't use ribbon mics at all, so I don't know what would happen with a
more difficult microphone than the common kinds of condensor mics that I
prefer.

These are two brand new Royer 122V Tube Ribbon Microphones. I sent
the first two I received back to Royer and they sent me two brand new
replacements. They told me to keep them away from dimmers, motors,
fluorescent lights, etc. They also mentioned that the mics can act
like antennas. If that is the case, then what can be done about it?
Could the problem originate in the power source and made worse by long
cable runs? I have to get in contact with them again and see what
they say as well. Perhaps getting shorter ribbon mic cables will
help, since you say the problem could be the ribbon mic cables acting
as antennas.

[Eeyore]

Truth wrote:

These are two brand new Royer 122V Tube Ribbon Microphones. I sent
the first two I received back to Royer

Why ? Same problem or a different one ?


and they sent me two brand new replacements. They told me to keep them away
from dimmers, motors,
fluorescent lights, etc. They also mentioned that the mics can act like
antennas.

They're talking crap. It probably means they know their design is defective.


If that is the case, then what can be done about it?

Reject them and buy something that works properly ?


Could the problem originate in the power source

If it was just a 'power source' it would be unlikely but it seems it contains some
active electronics (i.e it has gain). Certainly that electronics could be
defective. You sound a bit vague about understanding what you've bought.


and made worse by long cable runs?

Not really.


I have to get in contact with them again and see what
they say as well. Perhaps getting shorter ribbon mic cables will
help, since you say the problem could be the ribbon mic cables acting
as antennas.

It sounds like they've been pumping you full of nonsense.

Graham

[Truth]

On Sep 13, 12:27 pm, Eeyore
wrote:
Truth wrote:
These are two brand new Royer 122V Tube Ribbon Microphones. I sent
the first two I received back to Royer

Why ? Same problem or a different one ?

and they sent me two brand new replacements. They told me to keep them away
from dimmers, motors,
fluorescent lights, etc. They also mentioned that the mics can act like
antennas.

They're talking crap. It probably means they know their design is defective.

If that is the case, then what can be done about it?

Reject them and buy something that works properly ?

Could the problem originate in the power source

If it was just a 'power source' it would be unlikely but it seems it contains some
active electronics (i.e it has gain). Certainly that electronics could be
defective. You sound a bit vague about understanding what you've bought.

and made worse by long cable runs?

Not really.

I have to get in contact with them again and see what
they say as well. Perhaps getting shorter ribbon mic cables will
help, since you say the problem could be the ribbon mic cables acting
as antennas.

It sounds like they've been pumping you full of nonsense.

Graham

No they are correct. When my LCD monitor is on I can hear a definite
hum or buzz. When I turn it off it goes away, so I turn it off while
recording. Because the microphones use magnetism to function they are
prone to these problems. They sound good when they work, so I'd like
to try to see if the problem is not something other than the
microphones first.