[Alex]

I have a portable flash-memory recorder which has a mic input.

The input socket has "Plug-In-Power" this provides power to run a
suitably-designed unpowered electret mic which is plugged into the
socket.

If I use one of the older-style electret mics which contains a
battery for its own power then would that severely overload the input
electronics of the flash recorder?

If so then could such an arrangement actually cause damage to those
electronic components?

Alex



[ Basic tech info for Plug-In-Power = www.telinga.com/pipwp.htm ]

--


xposted to 4 groups GNKSA max:
sci.electronics.components
sci.electronics.repair
rec.audio.tech
alt.engineering.electrical

 

[[email protected]]

I have a portable flash-memory recorder which has a mic input.

The input socket has "Plug-In-Power" this provides power to run a
suitably-designed unpowered electret mic which is plugged into the
socket.

If I use one of the older-style electret mics which contains a
battery for its own power then would that severely overload the input
electronics of the flash recorder?

I'm presuming we're talking about a jack plug & socket here? Mono or
stereo? The jack plug has a tip and rings for the audio and DC power?
Maybe insertion of an unsuitable plug eg the one on your battery
powered mic might short the DC? Anything in the instructions/user
notes/online manual about that?

I wouldn't think that the signal level itself would cause damage. I
have used an 1980s Tandy stereo mike (with an new AA cell in the
barrel) with a PC sound card and I had to crank the input gain right up
compared with the cheapo (unpowered) mike in my webcam, not that that
proves anything much

Maybe a Google is order for a more specialised forum?

 

[[email protected]]

[email protected] wrote:

I looked belatedly at your link. I don't think you'll be damaging
anything.

 

[default]

I have a portable flash-memory recorder which has a mic input.

The input socket has "Plug-In-Power" this provides power to run a
suitably-designed unpowered electret mic which is plugged into the
socket.

If I use one of the older-style electret mics which contains a
battery for its own power then would that severely overload the input
electronics of the flash recorder?

If so then could such an arrangement actually cause damage to those
electronic components?

Alex



[ Basic tech info for Plug-In-Power = www.telinga.com/pipwp.htm ]

Try it with no battery installed. There is usually just an FET and
pull up resistor in it. Removing the battery should leave just the
FET and you'd have the pull up resistor/voltage source inside the
flash recorder - the way standard un powered electrets work.

 

[ian field]

Try it with no battery installed. There is usually just an FET and
pull up resistor in it. Removing the battery should leave just the
FET and you'd have the pull up resistor/voltage source inside the
flash recorder - the way standard un powered electrets work.

Doubtful - the output of the OP's powered mic appears to be capacitor
coupled, so there's no DC path to supply the FET.

 

[default]

Doubtful - the output of the OP's powered mic appears to be capacitor
coupled, so there's no DC path to supply the FET.

Well, cap coupled wouldn't work. I'd try it, nothing to lose, and
wouldn't you feel stupid if you didn't try that first?

 

[ian field]

No, since I don't expect it to work like that when its designed
properly. Also, you are applying a reverse voltage to the coupling
capacitor if you try this.

Since you mention that, if the cap is a tantalum even a small reverse
voltage can cause S/C failure - so it could work after all!!

 

[Michael A. Terrell]

Well, cap coupled wouldn't work. I'd try it, nothing to lose, and
wouldn't you feel stupid if you didn't try that first?

No, since I don't expect it to work like that when its designed
properly. Also, you are applying a reverse voltage to the coupling
capacitor if you try this.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Charles Schuler]

There is a dc blocking capacitor, so no damage will result.

 

[w9gb]

I have a portable flash-memory recorder which has a mic input.

The input socket has "Plug-In-Power" this provides power to run a
suitably-designed unpowered electret mic which is plugged into the
socket.

If I use one of the older-style electret mics which contains a
battery for its own power then would that severely overload the input
electronics of the flash recorder?

If so then could such an arrangement actually cause damage to those
electronic components?

Alex

[ Basic tech info for Plug-In-Power = www.telinga.com/pipwp.htm ]

When you have an equipment source that supplies power (phantom power) to an
elecret element -- everything is OK.

HOWEVER, IF you use other microphone elements (copper wound, magnetic
bobbin, dynamic) -- then the DC power must be de-coupled.
You use a capacitor to block this DC power. A 1 mFd. non-polar tantalum
capacitor in series with microphone lead. You may get by with a .68 or a .47
mFd but anything less (.01, .005 etc) will not pass any speech audio worth
listening to). The cap MUST be a non-polar. This will keep the D.C. from
getting across the dynamic element while passing the speech audio through
the cap into the mic preamp circuitry.

http://www.heilsound.com/amateur/harmonics.htm#DC

 

[w9gb]

Since you mention that, if the cap is a tantalum even a small reverse
voltage can cause S/C failure - so it could work after all!!

That is why a non-polar tantalum is used in this application.

 

[ian field]

That is why a non-polar tantalum is used in this application.

Didn't know such things exist! - got a pdf?

 

[w9gb]

Didn't know such things exist! - got a pdf?

GOOGLE is your Friend for Internet look-ups !

Non polar tantalum capacitor - US Patent 5777840
http://www.patentstorm.us/patents/5777840-description.html

Data sheets
http://www.digchip.com/datasheets/parts/st/parts_st41.php

Vishay
http://www.datasheetcatalog.com/datasheets_pdf/T/C/TC.shtml

Kemet FAQ
http://www.kemet.com/kemet/web/home...OpenDocument&source=find~~Capacitor+Selection

You can read it straight from Bob Heil (and yes he installs and sells these
with this products)
A non-polar electrolytic, if available, could also be used.

IF you use other microphone elements (copper wound, magnetic
bobbin, dynamic) -- on a "phantom powered" device ---
then the DC power must be de-coupled.
You use a capacitor to block this DC power.
A 1 mFd. non-polar tantalum capacitor in series with microphone lead. You
may get by with a .68 or a .47 mFd but anything less (.01, .005 etc) will
not pass any speech audio worth
listening to). The cap MUST be a non-polar. This will keep the D.C. from
getting across the dynamic element while passing the speech audio through
the cap into the mic preamp circuitry.
http://www.heilsound.com/amateur/harmonics.htm#DC