[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

[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

[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

[Mark]

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.

Are you saying you can hear the same squeal on the AM radio when you
listen to the station? Why is there a squeal on that station? Is the
station located near you...how far, how much power is it Tx? What
frequency is the AM station? What frequency is the squeal? Is you
audio equipment all analog or is the signal digitized at some point?
With what sampling rate?
The squeal may be an aliasing issue.

Mark

[Scott Dorsey]

Truth wrote:
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.

What kind if microphone? What kind of special cables? What kind of
preamp?

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?

Something has turned into a big antenna and is picking up RF... then something
else is rectifying it. It's very common for this to be a cable issue
combined with a preamp issue. Google "pin 1 problem" for one of the more
common sources.

Fixing either the pickup or the rectification will fix the problem, but it
would be wise to deal with both.

Can you hear the demodulated voice of the AM station?

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.

What IS this equipment?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[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."

[Arny Krueger]

"Scott Dorsey" wrote in message
...
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.

Probably a separate issue that coincidentally shows up.

[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, 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

[Richard Crowley]

"Truth" wrote ...
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.

As you know by now, throwing out generic anecdotes with
no details won't get you very far.

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.

You aren't supposed to hear ANY "squeal" when you listen to
radio (else nobody would listen). I would track down why you
are hearing this "squeal" even on a standalone radio (independent
of your problematic sound system). Call the radio station and
complain that you hear a squeal when you try to listen to them.
Could even be some kind of pirate radio station one of your
neighbors is transmitting, etc.

[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]

Scott Dorsey wrote:

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.

You got me there. Joke ?

Graham

[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

[Truth]

On Sep 13, 8:45 am, Mark wrote:
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.

Are you saying you can hear the same squeal on the AM radio when you
listen to the station? Why is there a squeal on that station? Is the
station located near you...how far, how much power is it Tx? What
frequency is the AM station? What frequency is the squeal? Is you
audio equipment all analog or is the signal digitized at some point?
With what sampling rate?
The squeal may be an aliasing issue.

Mark

790 AM
I get lots of squeal/whistle when I tune into that station on a
radio. I'm recording at 96K, 32bits. In reply to Paul Stamler I
listed my recording chain. Mostly digital. The Pendulum is a tube
preamp. When used with the ribbons I sometimes get a squeal. The
Weiss ADC2 can send out analog and digital. I'm sending out a DO to
the Lynx Two's DI.

[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.

[Truth]

On Sep 13, 12:02 pm, "Richard Crowley" wrote:
"Truth" wrote ...

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.

As you know by now, throwing out generic anecdotes with
no details won't get you very far.

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.

You aren't supposed to hear ANY "squeal" when you listen to
radio (else nobody would listen). I would track down why you
are hearing this "squeal" even on a standalone radio (independent
of your problematic sound system). Call the radio station and
complain that you hear a squeal when you try to listen to them.
Could even be some kind of pirate radio station one of your
neighbors is transmitting, etc.

It's a commercial station. 790 AM. I think the same station as some
talk shows. When I could hear the station it was a Christian Radio
Program.

[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

[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

[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.

[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

[Eeyore]

Truth wrote:

I even got some special power cords for the mic power supplies.

Why ? What did you expect it to do ? AC power doesn't need 'special cords'.
They're only for gullible 'audiophools'.

Graham

[Richard Crowley]

"Truth" wrote ...
It's a commercial station. 790 AM. I think the same station as some
talk shows. When I could hear the station it was a Christian Radio
Program.

If you are hearing the same "squeal", interference, etc. on this
radio receiver, why do you suspect anything is wrong with
your audio equipment?

Since we have no clue where you are "790 AM" means nothing
to us. There are 100 radio stations on that freuency just in
North America.

[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:

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, 12:20 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?

[Mike Rivers]

On Sep 13, 12:06 pm, Truth wrote:

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?

Move.

Could the problem originate in the power source and made worse by long
cable runs?

That's the easiest part to RF-proof, and I suspect that they've done a
reasonable job of it, but I don't know for sure. The RF could be being
picked up by the microphone element itself (there's only so much
shielding they can do and still let sound in), but it's not likely
that the cable is the problem. The output of the microphone is a
cathode follower, which I suspect does not go through a transformer,
at least not until it gets into the power supply box. That means an
unbalanced cable run which, even though it's a low impedance source
(the tube in the microphone) can still act as an antenna. The output
of the system is balanced, but it's not clear from the data I have
available where the balancing occurs. So you may very well have a 20
foot antenna ahead of your mic preamp. Or, if the RF field strength is
great enough, the tube in the mic could be acting like a diode and
detecting the radio signal.

You should try taking the mics and a preamp somewhere else. You don't
need the whole computer rig, just a set of headphones.

[Truth]

On Sep 13, 12:31 pm, Mike Rivers wrote:
On Sep 13, 12:06 pm, Truth wrote:

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?

Move.

Could the problem originate in the power source and made worse by long
cable runs?

That's the easiest part to RF-proof, and I suspect that they've done a
reasonable job of it, but I don't know for sure. The RF could be being
picked up by the microphone element itself (there's only so much
shielding they can do and still let sound in), but it's not likely
that the cable is the problem. The output of the microphone is a
cathode follower, which I suspect does not go through a transformer,
at least not until it gets into the power supply box. That means an
unbalanced cable run which, even though it's a low impedance source
(the tube in the microphone) can still act as an antenna. The output
of the system is balanced, but it's not clear from the data I have
available where the balancing occurs. So you may very well have a 20
foot antenna ahead of your mic preamp. Or, if the RF field strength is
great enough, the tube in the mic could be acting like a diode and
detecting the radio signal.

You should try taking the mics and a preamp somewhere else. You don't
need the whole computer rig, just a set of headphones.

I'm able to monitor direct from the Pendulum preamp and I hear the
squeal there before it gets to the computer. I'm thinking a shorter
run mic cable between the power box and mic might help.

[Don Pearce]

On Thu, 13 Sep 2007 09:36:00 -0700, Truth
wrote:

On Sep 13, 12:31 pm, Mike Rivers wrote:
On Sep 13, 12:06 pm, Truth wrote:

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?

Move.

Could the problem originate in the power source and made worse by long
cable runs?

That's the easiest part to RF-proof, and I suspect that they've done a
reasonable job of it, but I don't know for sure. The RF could be being
picked up by the microphone element itself (there's only so much
shielding they can do and still let sound in), but it's not likely
that the cable is the problem. The output of the microphone is a
cathode follower, which I suspect does not go through a transformer,
at least not until it gets into the power supply box. That means an
unbalanced cable run which, even though it's a low impedance source
(the tube in the microphone) can still act as an antenna. The output
of the system is balanced, but it's not clear from the data I have
available where the balancing occurs. So you may very well have a 20
foot antenna ahead of your mic preamp. Or, if the RF field strength is
great enough, the tube in the mic could be acting like a diode and
detecting the radio signal.

You should try taking the mics and a preamp somewhere else. You don't
need the whole computer rig, just a set of headphones.

I'm able to monitor direct from the Pendulum preamp and I hear the
squeal there before it gets to the computer. I'm thinking a shorter
run mic cable between the power box and mic might help.

Before you are forced to anything drastic, try some clamp-on RF
stoppers - the kind you find on the end of your VGA monitor cable. You
can get these in most electronics parts houses. Go for the lowest
frequency spec they have. Put them on all the cables (starting with
the mic cable) close to the preamp, and see which stops, or at least
reduces, the effect.

d
--
Pearce Consulting
http://www.pearce.uk.com

[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.

[Truth]

On Sep 13, 12:24 pm, "Richard Crowley" wrote:
"Truth" wrote ...

It's a commercial station. 790 AM. I think the same station as some
talk shows. When I could hear the station it was a Christian Radio
Program.

If you are hearing the same "squeal", interference, etc. on this
radio receiver, why do you suspect anything is wrong with
your audio equipment?

Since we have no clue where you are "790 AM" means nothing
to us. There are 100 radio stations on that freuency just in
North America.

That's the thing, I don't know what is the problem yet. It could be
the house lines acting as antenna and not the equipment itself which
is at fault. That's why I was asking if anyone thought the problem
was originating at the power source. Take a look at this article:

http://svconline.com/mag/avinstall_u...ontrolling_rf/
"Interference can also arrive via any wire coming into the building. "

[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.

[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.

[Truth]

On Sep 13, 12:22 pm, Eeyore
wrote:
Truth wrote:
I even got some special power cords for the mic power supplies.

Why ? What did you expect it to do ? AC power doesn't need 'special cords'.
They're only for gullible 'audiophools'.

Graham

Here are the cables I mentioned for the power supplies.

http://www.silversonic.com/docs/products/PowerPlus.html