repairing an electret microphone

[Dave Plowman (News)]

In article <-KidndVw-NH673_UnZ2dnUVZ_tydnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

"Dave Plowman (News)" wrote:

In article <I42dnYQ7-Ik6pH_UnZ2dnUVZ_uidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
In areas where there is still copper to the CO, a newer
form of phantom is used, by multiplexing multiple lines to a single
pair.

Crikey. How many other versions of 'phantom' are you going to use? Have
you ever written a technical spec?

Yes, but you won't be allowed to read them, without the proper
security clearance.

Wasn't the one for the Challenger O rings, was it?

--
*Arkansas State Motto: Don't Ask, Don't Tell, Don't Laugh.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Lynn]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:zpednYA1J7QlFX3UnZ2dnUVZ_qWdnZ2d@earthlink.com...

"Dave Plowman (News)" wrote:

In article <H8ZDl.7562$KB5.964@newsfe11.ams2>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:
Whoosh

Ah. Another term you don't understand.


You could fill a dozen phone books with terms you don't understand.

Explain: :Long Loop Video Combiner".


--
And another motherboard bites the dust!

Explain: Dirty Sanchez

 

[Arfa Daily]

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:504b0f9bc6dave@davenoise.co.uk...

In article <-KidndVw-NH673_UnZ2dnUVZ_tydnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

"Dave Plowman (News)" wrote:

In article <I42dnYQ7-Ik6pH_UnZ2dnUVZ_uidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
In areas where there is still copper to the CO, a newer
form of phantom is used, by multiplexing multiple lines to a single
pair.

Crikey. How many other versions of 'phantom' are you going to use? Have
you ever written a technical spec?


Yes, but you won't be allowed to read them, without the proper
security clearance.

Wasn't the one for the Challenger O rings, was it?

--

Now *that's* below the belt even for you ...

Arfa

 

[Arfa Daily]

"Tim Phipps" <news@timphipps.co.invalid> wrote in message
news:1XlEl.40543$ga.25238@newsfe01.ams2...

Arfa Daily wrote:


OK, but seems that all of this is tending to look at 'whole' mics as in
something that a newsreader would clip to himself, whereas the original
poster was talking about just the capsule inside, which was also what I
was referring to. As far as the polarity of electret mics varying, I
can't remember ever seeing a capsule where the case wasn't a
negative-side ground, and over the years, I have dealt with and replaced
many in cordless phones and similar.


IIRC the capsule in the Realistic (Tandy/RadioShack own brand) PZM
microphone had the +ve side connected to the case.

--
Tim Phipps

Fair enuff. Still, Tandy / Radio Hack says it all ...

Arfa

 

[Dave Plowman (News)]

In article <2vGEl.3783$rk7.2357@newsfe05.ams2>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:

IIRC the capsule in the Realistic (Tandy/RadioShack own brand) PZM
microphone had the +ve side connected to the case.

--
Tim Phipps


Fair enuff. Still, Tandy / Radio Hack says it all ...

Not only RS. Some pro mics which use an electret have the capsule body
reversed from the norm.

BTW, that original RadioShack PZM was a very good bit of kit.

--
*If you're not part of the solution, you're part of the precipitate *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

"Dave Plowman (News)" wrote:

In article <-KidndVw-NH673_UnZ2dnUVZ_tydnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

"Dave Plowman (News)" wrote:

In article <I42dnYQ7-Ik6pH_UnZ2dnUVZ_uidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
In areas where there is still copper to the CO, a newer
form of phantom is used, by multiplexing multiple lines to a single
pair.

Crikey. How many other versions of 'phantom' are you going to use? Have
you ever written a technical spec?

Yes, but you won't be allowed to read them, without the proper
security clearance.

Wasn't the one for the Challenger O rings, was it?

No, it was for the communications equipment in use when they
announced, "We have loss of Telemetry". Do you know what that means?




--
You can't have a sense of humor, if you have no sense!

 

[Michael A. Terrell]

Arfa Daily wrote:

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:504b0f9bc6dave@davenoise.co.uk...
In article <-KidndVw-NH673_UnZ2dnUVZ_tydnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

"Dave Plowman (News)" wrote:

In article <I42dnYQ7-Ik6pH_UnZ2dnUVZ_uidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
In areas where there is still copper to the CO, a newer
form of phantom is used, by multiplexing multiple lines to a single
pair.

Crikey. How many other versions of 'phantom' are you going to use? Have
you ever written a technical spec?


Yes, but you won't be allowed to read them, without the proper
security clearance.

Wasn't the one for the Challenger O rings, was it?

--

Now *that's* below the belt even for you ...

I'm beginning to believe he has EEyore disease.


--
You can't have a sense of humor, if you have no sense!

 

[Adrian Tuddenham]

Michael A. Terrell <mike.terrell@earthlink.net> wrote:

... No new phantom circuits have been
installed in decades.

Sorry to spoil your rant, but I used a phantom system to save on copper
when recording stereo from a remote position; I installed it last year.

It runs two high grade line-level audio circuits over dirt cheap 4-core
burglar alarm cable and the phantom can either be used for a third mic
or for talkback.


There's always one awkward so-and-so, isn't there....

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

 

[Dave Plowman (News)]

In article <1iy4gt1.1q1ewmn1v4u08uN%adrian@poppyrecords.invalid.invalid>,
Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote:

... No new phantom circuits have been
installed in decades.

Sorry to spoil your rant, but I used a phantom system to save on copper
when recording stereo from a remote position; I installed it last year.

It runs two high grade line-level audio circuits over dirt cheap 4-core
burglar alarm cable and the phantom can either be used for a third mic
or for talkback.

My recollection of when they were common in, say, outside broadcasts, was
that they were reserved for talkback use, due to the quality not being as
good as finite pairs. Of course over a relatively short run this might not
be noticeable.

Can I ask why you used burglar alarm cable rather than similar sized
telephone? It's just that telephone cable is twisted pair whereas alarm
usually not.

--
*Just remember...if the world didn't suck, we'd all fall off*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

Adrian Tuddenham wrote:

Michael A. Terrell <mike.terrell@earthlink.net> wrote:

... No new phantom circuits have been
installed in decades.

Sorry to spoil your rant, but I used a phantom system to save on copper
when recording stereo from a remote position; I installed it last year.

It runs two high grade line-level audio circuits over dirt cheap 4-core
burglar alarm cable and the phantom can either be used for a third mic
or for talkback.

How many miles? The circuits I saw were more than 20.

There's always one awkward so-and-so, isn't there....

That wasn't a telephone phantom circuit installed by a phone company,
was it? All references to them were removed for the phone company
manuals decades ago, and doesn't use WE or other phone company phantom
networks.

http://www.tpub.com/content/armycomsystems/SS0330/SS03300148.htm
http://www.tpub.com/content/armycomsystems/SS0330/SS03300149.htm

is a description of the circuit from some old Army manuals.


I ran the same kind of four conductor wire for a microphone, speaker,
transmit switch and a defeat switch for the tone squelch, but only
because there was no way to run new cable between a home brewed remote
head, and the outdoor mounted 330 W low band commercial FM base station.

I moved a school intercom console from one office, to another at the
other end of the building. There was no way to run more cable between
the separate foundations, and there weren't enough shielded lines run
when the addition was built, so I found an abandoned 16 pair 1A1
telephone cable and used it for the additional 12 classrooms. There are
thousands, or even millions of homebrew hacks that have been used from
time to time.


--
You can't have a sense of humor, if you have no sense!

 

[Tim Phipps]

Dave Plowman (News) wrote:

In article <2vGEl.3783$rk7.2357@newsfe05.ams2>,
Arfa Daily <arfa.daily@ntlworld.com> wrote:
IIRC the capsule in the Realistic (Tandy/RadioShack own brand) PZM
microphone had the +ve side connected to the case.

--
Tim Phipps


Fair enuff. Still, Tandy / Radio Hack says it all ...

Not only RS. Some pro mics which use an electret have the capsule body
reversed from the norm.

BTW, that original RadioShack PZM was a very good bit of kit.

Agreed, it was one of the few decent things you could buy in Tandy.
Although it came with an unbalanced jack fitted, its output was actually
balanced so all one had to do was cut the plug off and fit an XLR instead

--
Tim Phipps

replace "invalid" with "uk" to reply by email

 

[Adrian Tuddenham]

Dave Plowman (News) <dave@davenoise.co.uk> wrote:

In article <1iy4gt1.1q1ewmn1v4u08uN%adrian@poppyrecords.invalid.invalid>,
Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote:
... No new phantom circuits have been
installed in decades.

Sorry to spoil your rant, but I used a phantom system to save on copper
when recording stereo from a remote position; I installed it last year.

It runs two high grade line-level audio circuits over dirt cheap 4-core
burglar alarm cable and the phantom can either be used for a third mic
or for talkback.

My recollection of when they were common in, say, outside broadcasts, was
that they were reserved for talkback use, due to the quality not being as
good as finite pairs. Of course over a relatively short run this might not
be noticeable.

Over a 100 metre run, the phantom was quite good enough for a
full-bandwidth (20c/s - 20Kc/s) mic circuit. As it is usually the
terminating equipment that determines the quality on 'short' lines, I
would not expect much worse over a kilometre or two.

The crosstalk of the phantom to the outer pairs was around 60dB at
10Kc/s whereas the pair-to-pair crosstalk was better than 80dB (both
worsened at 6dB/octave). That might vary with line balance and is also
affected by the physical arrangement of the transformers, which all had
to be mounted in the same box and did not have any screening pots.

It would even have been possible to run a 100v P.A. line as talkback on
the phantom, because the breakthrough would only occur when the side
pairs weren't carrying live programme.

Can I ask why you used burglar alarm cable rather than similar sized
telephone? It's just that telephone cable is twisted pair whereas alarm
usually not.

It was the cheapest four-core flexible cable in the Radiospares
catalogue and it was twisted with a constant physical relationship
between the cores. Telephone twised pair would have been fine for a
fixed installation, but this was for occasional 'outside broadcast' type
of use where a a lot of bending could occur, so a flexible type was
preferred.

Normally cost of the terminating equipment would make such an
arrangement uneconomical for 'short' lines of a few kilometres (or even
less in this particular case), but the mics already had built-in preamps
which delivered 0dBm level and the transformers were part of a surplus
job lot which I obtained cheaply many years ago.

Given the choice between buying expensive mic cables or buying burglar
alarm cable and sticking some spare transformers in a box, I decided to
give phantoming a try - and was pleasantly surprised by the results.


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

 

[Adrian Tuddenham]

Michael A. Terrell <mike.terrell@earthlink.net> wrote:

Adrian Tuddenham wrote:

Michael A. Terrell <mike.terrell@earthlink.net> wrote:

... No new phantom circuits have been
installed in decades.

Sorry to spoil your rant, but I used a phantom system to save on copper
when recording stereo from a remote position; I installed it last year.

It runs two high grade line-level audio circuits over dirt cheap 4-core
burglar alarm cable and the phantom can either be used for a third mic
or for talkback.


How many miles? The circuits I saw were more than 20.

The test run was only 100 metres, but runs up to a couple of kilometeres
may be used in future. (See my other reply for the reason this was
economical in this particular case)

That wasn't a telephone phantom circuit installed by a phone company,
was it?

No, although there is no engineering reason why a telephone circuit
could not be used.

I ran the same kind of four conductor wire for a microphone, speaker,
transmit switch and a defeat switch for the tone squelch, but only
because there was no way to run new cable between a home brewed remote
head, and the outdoor mounted 330 W low band commercial FM base station.

I moved a school intercom console from one office, to another at the
other end of the building. There was no way to run more cable between
the separate foundations, and there weren't enough shielded lines run
when the addition was built, so I found an abandoned 16 pair 1A1
telephone cable and used it for the additional 12 classrooms. There are
thousands, or even millions of homebrew hacks that have been used from
time to time.

This is where someone with a good wide working knowledge of electronics
can achieve the 'impossible' while the graduate engineer is still saying
it can't be done.


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

 

[Dave Plowman (News)]

In article <1iy5ooy.7rjnp8cxbbvwN%adrian@poppyrecords.invalid.invalid>,
Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote:

Can I ask why you used burglar alarm cable rather than similar sized
telephone? It's just that telephone cable is twisted pair whereas alarm
usually not.

It was the cheapest four-core flexible cable in the Radiospares
catalogue and it was twisted with a constant physical relationship
between the cores. Telephone twised pair would have been fine for a
fixed installation, but this was for occasional 'outside broadcast' type
of use where a a lot of bending could occur, so a flexible type was
preferred.

Right. I must admit to being surprised that it's strong enough for that
sort of use. But if it works, that's all that matters.

Normally cost of the terminating equipment would make such an
arrangement uneconomical for 'short' lines of a few kilometres (or even
less in this particular case), but the mics already had built-in preamps
which delivered 0dBm level and the transformers were part of a surplus
job lot which I obtained cheaply many years ago.

Given the choice between buying expensive mic cables or buying burglar
alarm cable and sticking some spare transformers in a box, I decided to
give phantoming a try - and was pleasantly surprised by the results.

Yes - I've played with it here. Acquired a load of rep coils from a
redundant facility.

My comments about a phantom circuit not performing as well as a copper
pair date back to using them from a remote OB location back to studio
centre. And it's quite possible the two pairs that hosted it went by
different routes. So had rather different characteristics.

--
Small asylum seeker wanted as mud flap, must be flexible and willing to travel

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Adrian Tuddenham]

Dave Plowman (News) <dave@davenoise.co.uk> wrote:

In article <1iy5ooy.7rjnp8cxbbvwN%adrian@poppyrecords.invalid.invalid>,
Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote:
Can I ask why you used burglar alarm cable rather than similar sized
telephone? It's just that telephone cable is twisted pair whereas alarm
usually not.

It was the cheapest four-core flexible cable in the Radiospares
catalogue and it was twisted with a constant physical relationship
between the cores. Telephone twised pair would have been fine for a
fixed installation, but this was for occasional 'outside broadcast' type
of use where a a lot of bending could occur, so a flexible type was
preferred.

Right. I must admit to being surprised that it's strong enough for that
sort of use. But if it works, that's all that matters.

For the difference in price, it is worth the extra effort of being
gentle with it. I don't let anyone else do the rigging.

Given the choice between buying expensive mic cables or buying burglar
alarm cable and sticking some spare transformers in a box, I decided to
give phantoming a try - and was pleasantly surprised by the results.

Yes - I've played with it here. Acquired a load of rep coils from a
redundant facility.

My comments about a phantom circuit not performing as well as a copper
pair date back to using them from a remote OB location back to studio
centre. And it's quite possible the two pairs that hosted it went by
different routes. So had rather different characteristics.

That sort of routing might work at DC, but I wouldn't trust it above
50c/s. If the phantom is 'official' the telephone people ought to
ensure that it is always run on two adjacent pairs; I have even heard of
a long route where the phantom signal was on a separate pair for part of
the route and only phantomed on the congested bits.

My phantom is always in the same cable, so I don't need to worry about
the pairs getting separated.


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