[[email protected]]

Hey folks.

I know there are some fans of this mic like me here so...

My MD1a is working great except for one thing. It has a faint high pitched intermittent whistle. It seems like it happens after the mic has been powered up for a while.... but I may be wrong on that.

I've swapped out the tube assuming it was microphonic, but the same issue is still here. Hmmmmmm.

Any thoughts or who would you send it to?

Many thanks!

[Scott Dorsey]

wrote:
I know there are some fans of this mic like me here so...

My MD1a is working great except for one thing. It has a faint high pitched intermittent whistle. It seems like it happens after the mic has been powered up for a while.... but I may be wrong on that.

I've swapped out the tube assuming it was microphonic, but the same issue is still here. Hmmmmmm.

Any thoughts or who would you send it to?

Either it's oscillating (usually this is the result of poor circuit board
layout combined with dirt and dust getting on the board or capsule) or
it's picking up RF noise.

If you move it around and the noise changes with position, it's an RF noise
issue.

Microphonic tubes won't oscillate or whistle, they will boing.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

On Monday, December 31, 2012 10:12:12 AM UTC-5, Scott Dorsey wrote:
wrote:

I know there are some fans of this mic like me here so...



My MD1a is working great except for one thing. It has a faint high pitched intermittent whistle. It seems like it happens after the mic has been powered up for a while.... but I may be wrong on that.



I've swapped out the tube assuming it was microphonic, but the same issue is still here. Hmmmmmm.



Any thoughts or who would you send it to?



Either it's oscillating (usually this is the result of poor circuit board

layout combined with dirt and dust getting on the board or capsule) or

it's picking up RF noise.



If you move it around and the noise changes with position, it's an RF noise

issue.



Microphonic tubes won't oscillate or whistle, they will boing.

--scott

--

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

Thanks for that input Scott

Moving it around the room has no effect.
As to it's cleanliness, it looks clean to the naked eye inside.

I just took it up to JJ Audio in Maryland. We'll see if he finds anything. although we couldn't get it to make the sound in the 1/2 I sat there. (Of course).

[Lord Valve]

Scott Dorsey wrote:

Microphonic tubes won't oscillate or whistle, they will boing.

Absolutely wrong.

A microphonic tube can certainly whistle. It's
called "feedback" - YOU know, like microphones
do? Happens all the time, especially in guitar
amps, where the tubes are often less than six inches
from the speakers. Tubes can also make putt-putt
noises, roar like a waterfall, sizzle like frying bacon,
hiss, intermittently pop, fizz, crackle, buzz, hum,
rattle, jingle, and shriek like a steam whistle.
And those are just *some* of the noises I've
personally heard tubes make. Hell, if a tube is
microphonic enough, you can *talk* close to it
and your voice will come out of the speaker.

That's why they call it "microphonic," see?


Lord Valve
Toob Dood

[geoff]

"Lord Valve" wrote in message
...
Scott Dorsey wrote:

Microphonic tubes won't oscillate or whistle, they will boing.

Absolutely wrong.

A microphonic tube can certainly whistle. It's
called "feedback" - YOU know, like microphones
do? Happens all the time, especially in guitar
amps, where the tubes are often less than six inches
from the speakers. Tubes can also make putt-putt
noises, roar like a waterfall, sizzle like frying bacon,
hiss, intermittently pop, fizz, crackle, buzz, hum,
rattle, jingle, and shriek like a steam whistle.
And those are just *some* of the noises I've
personally heard tubes make. Hell, if a tube is
microphonic enough, you can *talk* close to it
and your voice will come out of the speaker.

That's why they call it "microphonic," see?


Lord Valve
Toob Dood

Sure can - all of the above !

Hey LV, would you mind terribly if I contacted you by email privately
regarding a subject relating to this, but a little too OT for r.a.p ? My
email is as indicated, but without the 'nospam'.

cheers

geoff

[geoff]

"geoff" wrote in message
...



..... and can anybody recoomend a job newgroup specialising in guitar amp
repair ? The 'obvious' ones I've tried appear to be simply full of crap.
Far more even than here !

geoff

[[email protected]]

On Monday, December 31, 2012 5:06:35 PM UTC-5, wrote:
On Monday, December 31, 2012 10:12:12 AM UTC-5, Scott Dorsey wrote:

wrote:



I know there are some fans of this mic like me here so...







My MD1a is working great except for one thing. It has a faint high pitched intermittent whistle. It seems like it happens after the mic has been powered up for a while.... but I may be wrong on that.







I've swapped out the tube assuming it was microphonic, but the same issue is still here. Hmmmmmm.







Any thoughts or who would you send it to?







Either it's oscillating (usually this is the result of poor circuit board



layout combined with dirt and dust getting on the board or capsule) or



it's picking up RF noise.







If you move it around and the noise changes with position, it's an RF noise



issue.







Microphonic tubes won't oscillate or whistle, they will boing.



--scott



--



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



Thanks for that input Scott



Moving it around the room has no effect.

As to it's cleanliness, it looks clean to the naked eye inside.



I just took it up to JJ Audio in Maryland. We'll see if he finds anything. although we couldn't get it to make the sound in the 1/2 I sat there. (Of course).

As I guessed, he couldn't replicate the noise.
He did suggest I rebuild the power supply but honestly I don't think it's needed since it powers the mic fine otherwise.

Ughhh.

[Scott Dorsey]

wrote:
As I guessed, he couldn't replicate the noise.
He did suggest I rebuild the power supply but honestly I don't think it's needed since it powers the mic fine otherwise.

That's another suggestion that it might be an RF issue.
--scott


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

[[email protected]]

On Thursday, January 3, 2013 1:57:21 PM UTC-5, Scott Dorsey wrote:
wrote:

As I guessed, he couldn't replicate the noise.

He did suggest I rebuild the power supply but honestly I don't think it's needed since it powers the mic fine otherwise.



That's another suggestion that it might be an RF issue.

--scott





--

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

Hmmmm.
Is there anything "reasonable" I can do to prevent this or lessen its effects.
Funny thing is (now that I think about it) there are a lot more wireless device floating around my home (studio).

[Les Cargill[_4_]]

wrote:
On Thursday, January 3, 2013 1:57:21 PM UTC-5, Scott Dorsey wrote:
wrote:

As I guessed, he couldn't replicate the noise.

He did suggest I rebuild the power supply but honestly I don't think it's needed since it powers the mic fine otherwise.



That's another suggestion that it might be an RF issue.

--scott





--

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

Hmmmm.
Is there anything "reasonable" I can do to prevent this or lessen its effects.
Funny thing is (now that I think about it) there are a lot more wireless device floating around my home (studio).


It may not be external the the preamp and mic.

I have a Symmetrix SX202 mic amp that whistles with some Marshall
603S SD condensers*. - I just use a different preamp with those mics
or filter it in post. I took that as an opportunity to
implement a digital notch filter.

*one or both; frequency changes with number of mics. there's a buck
converter in the Symmetrix.

Scott recommended the Shure RF filters when I asked about it here, but
I haven't done that yet.

Turns out Full Compass has them in stock:
http://www.fullcompass.com/product/260981.html

--
Les Cargill

[[email protected]]

On Thursday, January 3, 2013 6:30:55 PM UTC-5, Les Cargill wrote:
wrote:

On Thursday, January 3, 2013 1:57:21 PM UTC-5, Scott Dorsey wrote:

wrote:



As I guessed, he couldn't replicate the noise.



He did suggest I rebuild the power supply but honestly I don't think it's needed since it powers the mic fine otherwise.







That's another suggestion that it might be an RF issue.



--scott











--



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



Hmmmm.

Is there anything "reasonable" I can do to prevent this or lessen its effects.

Funny thing is (now that I think about it) there are a lot more wireless device floating around my home (studio).





It may not be external the the preamp and mic.



I have a Symmetrix SX202 mic amp that whistles with some Marshall

603S SD condensers*. - I just use a different preamp with those mics

or filter it in post. I took that as an opportunity to

implement a digital notch filter.



*one or both; frequency changes with number of mics. there's a buck

converter in the Symmetrix.



Scott recommended the Shure RF filters when I asked about it here, but

I haven't done that yet.



Turns out Full Compass has them in stock:

http://www.fullcompass.com/product/260981.html



--

Les Cargill

Just to recap..... (no pun intended), the sound is a high freq whistle and is in short bursts about 2-5 seconds long. Faint.

Wouldn't RF be constant?

Just asking.

Thanks

[Les Cargill[_4_]]

wrote:
On Thursday, January 3, 2013 6:30:55 PM UTC-5, Les Cargill wrote:
snip
Just to recap..... (no pun intended), the sound is a high freq whistle and is in short bursts about 2-5 seconds long. Faint.


Are they periodic bursts? Can you add an H pad and see if they go away?

Wouldn't RF be constant?


I am thinking we mean "RF coupled oscillation". So maybe, maybe not.

Just asking.

Thanks


--
Les Cargill

[[email protected]]

H Pad?

[Les Cargill[_4_]]

wrote:
H Pad?



http://www.nu9n.com/tpad-calculator.html

--
Les Cargill

[david gourley[_2_]]

said...news:6c687ee1-16aa-453a-a4bb-84dcda4c24b2
@googlegroups.com:

snippage


Just to recap..... (no pun intended), the sound is a high freq whistle
and is in short bursts about 2-5 seconds long. Faint.

Wouldn't RF be constant?

Just asking.

Thanks

Is this the model with the Josephson capsule?

I think there were grounding issues reported with some of those mics, so
you may want to check those connections. It's probably something simple.

david

[Scott Dorsey]

wrote:

Just to recap..... (no pun intended), the sound is a high freq whistle and is in short bursts about 2-5 seconds long. Faint.

That is not typical oscillation. That sounds a lot like RF.

Wouldn't RF be constant?

Not if it's coming from a source that isn't constant, like a paging transmitter
or a cellphone or a traffic light controller.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

david gourley wrote:
said...news:6c687ee1-16aa-453a-a4bb-84dcda4c24b2
:

snippage


Just to recap..... (no pun intended), the sound is a high freq whistle
and is in short bursts about 2-5 seconds long. Faint.

Wouldn't RF be constant?

Just asking.

Thanks

Is this the model with the Josephson capsule?

I think there were grounding issues reported with some of those mics, so
you may want to check those connections. It's probably something simple.

I'd check to make sure there was a VERY good connection from the case of
the mike to the cable ground, and that the load ground is very solid. Would
not hurt to just polish connections a bit.

If the case is not well-grounded, RF is going to leak in and eventually
it will get rectified somewhere.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Lord Valve]

wrote:

On Thursday, January 3, 2013 6:30:55 PM UTC-5, Les Cargill wrote:
wrote:

On Thursday, January 3, 2013 1:57:21 PM UTC-5, Scott Dorsey wrote:

wrote:



As I guessed, he couldn't replicate the noise.



He did suggest I rebuild the power supply but honestly I don't think it's needed since it powers the mic fine otherwise.







That's another suggestion that it might be an RF issue.



--scott











--



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



Hmmmm.

Is there anything "reasonable" I can do to prevent this or lessen its effects.

Funny thing is (now that I think about it) there are a lot more wireless device floating around my home (studio).





It may not be external the the preamp and mic.



I have a Symmetrix SX202 mic amp that whistles with some Marshall

603S SD condensers*. - I just use a different preamp with those mics

or filter it in post. I took that as an opportunity to

implement a digital notch filter.



*one or both; frequency changes with number of mics. there's a buck

converter in the Symmetrix.



Scott recommended the Shure RF filters when I asked about it here, but

I haven't done that yet.



Turns out Full Compass has them in stock:

http://www.fullcompass.com/product/260981.html



--

Les Cargill

Just to recap..... (no pun intended), the sound is a high freq whistle and is in short bursts about 2-5 seconds long. Faint.

Wouldn't RF be constant?

Just asking.

Thanks

Cellphone.

Cellphones talk to Mom every few minutes or so, so that
Mom always knows where they are.

LV

[Don Pearce[_3_]]

On Thu, 3 Jan 2013 19:06:48 -0800 (PST), wrote:

Just to recap..... (no pun intended), the sound is a high freq whistle and is in short bursts about 2-5 seconds long. Faint.

Wouldn't RF be constant?

You aren't near an airport, by any chance? Could ground radar.

d

[[email protected]]

No airport.... Frankly, I live in the sticks.
I do have an airport wifi hub though.... And Hughesnet satellite Internet..... Hmmmm

[John Williamson]

Lord Valve wrote:
wrote:

Just to recap..... (no pun intended), the sound is a high freq whistle and is in short bursts about 2-5 seconds long. Faint.

Wouldn't RF be constant?

Just asking.

Thanks

Cellphone.

Cellphones talk to Mom every few minutes or so, so that
Mom always knows where they are.

They also make a very distinctve sound in the RF interference spectrum,
which once heard, is easily recognised. What's being described is more
likely to be something like a wireless thermostat or something to do
with a wireless burglar alarm polling its sensors. It would make life a
lot easier if the OP were to link to a recording of the interference.
Someone would probably listen to it and immediately say "Oh, yes, it's
XXXXXXXX"


--
Tciao for Now!

John.

[[email protected]]

Near Charlottesville VA.
In DC/MD once a week though for work.