I have extracted the dual electret mic board from a defunct Zoom H2. I
would like to wire these and use as external mics for a working H2, but
need wire. I'm trying to capture some bird songs emanating from trees
on my property and want to try strategically placing this small board in
areas of the trees where I've seen the birds. Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately
and just use the output from the Zoom, just to keep things simple. Mic
wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only
when I'm attempting a capture session.

Thank you.

---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom H2. I
would like to wire these and use as external mics for a working H2, but
need wire. I'm trying to capture some bird songs emanating from trees
on my property and want to try strategically placing this small board in areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the proximity of the board will badly affect the frequency response and the directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh or a
sieve. Better still, attach them to a plastic-coated coat-hanger which
can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately
and just use the output from the Zoom, just to keep things simple. Mic
wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only
when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can tolerate quite a bit of capacitance before you start to lose the high frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would
be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre,
so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant
compared with the 600 ohm microphone, so voltage loss will be negligible
too.

The cable has four cores which can be connected for stereo if you aren't worried about a bit of cross-talk. If you need low cross talk - or if
there is a lot of electrical interference - two cables can be use, each
wired as starquad. If you find you are picking up radio stations, wnd a
few turns of the cable around a ferrite core immediately adjacent to the recorder.

I have used ordinary house-wiring multicore telephone cable for this in
the past, with no screen at all, and the results have been perfectly acceptable. If you can't get any cheap screened Ethernet cable, try the unscreened type and see what happens.

If you are lucky, a computer systems installer might let you raid his
scrap bin and you could get a couple of 10-metre lengths of Ethernet
cable for free.


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

---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

On 25/03/2026 13:06, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom H2. I
would like to wire these and use as external mics for a working H2, but
need wire. I'm trying to capture some bird songs emanating from trees
on my property and want to try strategically placing this small board in
areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the proximity of the board will badly affect the frequency response and the directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh or a sieve. Better still, attach them to a plastic-coated coat-hanger which
can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately
and just use the output from the Zoom, just to keep things simple. Mic
wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only
when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can tolerate quite a bit of capacitance before you start to lose the high frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would
be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre,
so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant compared with the 600 ohm microphone, so voltage loss will be negligible
too.

The cable has four cores which can be connected for stereo if you aren't worried about a bit of cross-talk. If you need low cross talk - or if
there is a lot of electrical interference - two cables can be use, each
wired as starquad. If you find you are picking up radio stations, wnd a
few turns of the cable around a ferrite core immediately adjacent to the recorder.

I have used ordinary house-wiring multicore telephone cable for this in
the past, with no screen at all, and the results have been perfectly acceptable. If you can't get any cheap screened Ethernet cable, try the unscreened type and see what happens.

Twisted pairs balance out most EM interference on long runs.


--
Tciao for Now!

John.

---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

On 3/25/26 9:06 AM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom H2. I
would like to wire these and use as external mics for a working H2, but
need wire. I'm trying to capture some bird songs emanating from trees
on my property and want to try strategically placing this small board in
areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the proximity of the board will badly affect the frequency response and the directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh or a sieve. Better still, attach them to a plastic-coated coat-hanger which
can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Thanks for the tip. Actually, I was just going to leave them on the
board with no attachments but I hadn't thought of mounting them in the
tree yet. The plastic coat hanger sounds like a great idea, however.

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately
and just use the output from the Zoom, just to keep things simple. Mic
wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only
when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can tolerate quite a bit of capacitance before you start to lose the high frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would
be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre,
so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant compared with the 600 ohm microphone, so voltage loss will be negligible
too.

The cable has four cores which can be connected for stereo if you aren't worried about a bit of cross-talk. If you need low cross talk - or if
there is a lot of electrical interference - two cables can be use, each
wired as starquad. If you find you are picking up radio stations, wnd a
few turns of the cable around a ferrite core immediately adjacent to the recorder.

I have used ordinary house-wiring multicore telephone cable for this in
the past, with no screen at all, and the results have been perfectly acceptable. If you can't get any cheap screened Ethernet cable, try the unscreened type and see what happens.

If you are lucky, a computer systems installer might let you raid his
scrap bin and you could get a couple of 10-metre lengths of Ethernet
cable for free.

Actually I have about 10,000 feet of unscreened 4 conductor Ethernet
cable I picked up at a yard sale some years back. I've used pieces here
and there for a variety of things, but mainly separated out the twisted
pairs and used as a radial ground screen for an antenna I built some
years ago. Cheap and worked great. I never thought of using them as
mic wire since they lacked the screen, but will give it a try first.
Thanks for mentioning this option!





---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

John Williamson <johnwilliamson@btinternet.com> wrote:

On 25/03/2026 13:06, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom H2. I
would like to wire these and use as external mics for a working H2, but
need wire. I'm trying to capture some bird songs emanating from trees
on my property and want to try strategically placing this small board in >> areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the proximity of the board will badly affect the frequency response and the directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh or a sieve. Better still, attach them to a plastic-coated coat-hanger which
can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately
and just use the output from the Zoom, just to keep things simple. Mic
wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only
when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can tolerate quite a bit of capacitance before you start to lose the high frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would
be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre,
so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant compared with the 600 ohm microphone, so voltage loss will be negligible too.

The cable has four cores which can be connected for stereo if you aren't worried about a bit of cross-talk. If you need low cross talk - or if there is a lot of electrical interference - two cables can be use, each wired as starquad. If you find you are picking up radio stations, wnd a few turns of the cable around a ferrite core immediately adjacent to the recorder.

I have used ordinary house-wiring multicore telephone cable for this in
the past, with no screen at all, and the results have been perfectly acceptable. If you can't get any cheap screened Ethernet cable, try the unscreened type and see what happens.

Twisted pairs balance out most EM interference on long runs.

Yes, I have seen professional tape recorders that were intended to be
used with very long runs of unscreened twisted flex, but the microphone impedance was 30 ohms.

The signal levels on 600-ohm microphone cables are 50dB lower than in
balanced open-wire pairs, so the noise rejection needs to be at least
50dB better. If you are using the pair for professional recordings,
rather than telephone conversations, you would want it to be even better
than that.

You might get away without screening but screened Ethernet cable is not
hugely more expensive than the cheapest unscreened type and will
guarantee good noise performance, rather than just hoping for the best.


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

---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

George Garth <none@nowhere.com> wrote:

On 3/25/26 9:06 AM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom H2. I
would like to wire these and use as external mics for a working H2, but
need wire. I'm trying to capture some bird songs emanating from trees
on my property and want to try strategically placing this small board in >> areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the proximity of the board will badly affect the frequency response and the directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh or a sieve. Better still, attach them to a plastic-coated coat-hanger which
can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Thanks for the tip. Actually, I was just going to leave them on the
board with no attachments but I hadn't thought of mounting them in the
tree yet. The plastic coat hanger sounds like a great idea, however.

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately
and just use the output from the Zoom, just to keep things simple. Mic
wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only
when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can tolerate quite a bit of capacitance before you start to lose the high frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would
be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre,
so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant compared with the 600 ohm microphone, so voltage loss will be negligible too.

The cable has four cores which can be connected for stereo if you aren't worried about a bit of cross-talk. If you need low cross talk - or if there is a lot of electrical interference - two cables can be use, each wired as starquad. If you find you are picking up radio stations, wnd a few turns of the cable around a ferrite core immediately adjacent to the recorder.

I have used ordinary house-wiring multicore telephone cable for this in
the past, with no screen at all, and the results have been perfectly acceptable. If you can't get any cheap screened Ethernet cable, try the unscreened type and see what happens.

If you are lucky, a computer systems installer might let you raid his
scrap bin and you could get a couple of 10-metre lengths of Ethernet
cable for free.

Actually I have about 10,000 feet of unscreened 4 conductor Ethernet
cable I picked up at a yard sale some years back. I've used pieces here
and there for a variety of things, but mainly separated out the twisted
pairs and used as a radial ground screen for an antenna I built some
years ago. Cheap and worked great. I never thought of using them as
mic wire since they lacked the screen, but will give it a try first.
Thanks for mentioning this option!

That sounds very promising and it will cost you nothing to experiment a
bit. If you use two separate runs, wired as starquad, and wind them a
few turns through a toriod or two, I would be very surprised if you find
any problems.

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

---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

On 3/25/26 1:59 PM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

On 3/25/26 9:06 AM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom H2. I >>>> would like to wire these and use as external mics for a working H2, but >>>> need wire. I'm trying to capture some bird songs emanating from trees >>>> on my property and want to try strategically placing this small board in >>>> areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the
proximity of the board will badly affect the frequency response and the
directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh or a >>> sieve. Better still, attach them to a plastic-coated coat-hanger which
can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Thanks for the tip. Actually, I was just going to leave them on the
board with no attachments but I hadn't thought of mounting them in the
tree yet. The plastic coat hanger sounds like a great idea, however.

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately
and just use the output from the Zoom, just to keep things simple. Mic >>>> wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only >>>> when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can
tolerate quite a bit of capacitance before you start to lose the high
frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would
be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre,
so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant
compared with the 600 ohm microphone, so voltage loss will be negligible >>> too.

The cable has four cores which can be connected for stereo if you aren't >>> worried about a bit of cross-talk. If you need low cross talk - or if
there is a lot of electrical interference - two cables can be use, each
wired as starquad. If you find you are picking up radio stations, wnd a >>> few turns of the cable around a ferrite core immediately adjacent to the >>> recorder.

I have used ordinary house-wiring multicore telephone cable for this in
the past, with no screen at all, and the results have been perfectly
acceptable. If you can't get any cheap screened Ethernet cable, try the >>> unscreened type and see what happens.

If you are lucky, a computer systems installer might let you raid his
scrap bin and you could get a couple of 10-metre lengths of Ethernet
cable for free.

Actually I have about 10,000 feet of unscreened 4 conductor Ethernet
cable I picked up at a yard sale some years back. I've used pieces here
and there for a variety of things, but mainly separated out the twisted
pairs and used as a radial ground screen for an antenna I built some
years ago. Cheap and worked great. I never thought of using them as
mic wire since they lacked the screen, but will give it a try first.
Thanks for mentioning this option!

That sounds very promising and it will cost you nothing to experiment a
bit. If you use two separate runs, wired as starquad, and wind them a
few turns through a toriod or two, I would be very surprised if you find
any problems.

Thanks, Liz. Sorry I didn't respond sooner, but I am not familiar with "starquad" and would appreciate exactly how this is set up. It needs
two runs of the 4 conductor Ethernet cable? Also, any particular
ferrite? Snap together type or toroid?


---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

On 28/03/2026 16:12, George Garth wrote:

On 3/25/26 1:59 PM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

On 3/25/26 9:06 AM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom
H2. I
would like to wire these and use as external mics for a working H2,
but
need wire. I'm trying to capture some bird songs emanating from trees >>>>> on my property and want to try strategically placing this small
board in
areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the >>>> proximity of the board will badly affect the frequency response and the >>>> directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh
or a
sieve. Better still, attach them to a plastic-coated coat-hanger which >>>> can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Thanks for the tip. Actually, I was just going to leave them on the
board with no attachments but I hadn't thought of mounting them in the
tree yet. The plastic coat hanger sounds like a great idea, however.

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately >>>>> and just use the output from the Zoom, just to keep things simple.
Mic
wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only >>>>> when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can >>>> tolerate quite a bit of capacitance before you start to lose the high
frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would >>>> be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre, >>>> so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant
compared with the 600 ohm microphone, so voltage loss will be
negligible
too.

The cable has four cores which can be connected for stereo if you
aren't
worried about a bit of cross-talk. If you need low cross talk - or if >>>> there is a lot of electrical interference - two cables can be use, each >>>> wired as starquad. If you find you are picking up radio stations,
wnd a
few turns of the cable around a ferrite core immediately adjacent to
the
recorder.

I have used ordinary house-wiring multicore telephone cable for this in >>>> the past, with no screen at all, and the results have been perfectly
acceptable. If you can't get any cheap screened Ethernet cable, try
the
unscreened type and see what happens.

If you are lucky, a computer systems installer might let you raid his
scrap bin and you could get a couple of 10-metre lengths of Ethernet
cable for free.

Actually I have about 10,000 feet of unscreened 4 conductor Ethernet
cable I picked up at a yard sale some years back. I've used pieces here >>> and there for a variety of things, but mainly separated out the twisted
pairs and used as a radial ground screen for an antenna I built some
years ago. Cheap and worked great. I never thought of using them as
mic wire since they lacked the screen, but will give it a try first.
Thanks for mentioning this option!

That sounds very promising and it will cost you nothing to experiment a
bit. If you use two separate runs, wired as starquad, and wind them a
few turns through a toriod or two, I would be very surprised if you find
any problems.

Thanks, Liz. Sorry I didn't respond sooner, but I am not familiar with "starquad" and would appreciate exactly how this is set up. It needs
two runs of the 4 conductor Ethernet cable? Also, any particular
ferrite? Snap together type or toroid?

https://www.soundonsound.com/sound-advice/q-whats-special-about-star-quad-cable

--
Tciao for Now!

John.

---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)

George Garth <none@nowhere.com> wrote:

On 3/25/26 1:59 PM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

On 3/25/26 9:06 AM, Liz Tuddenham wrote:

George Garth <none@nowhere.com> wrote:

I have extracted the dual electret mic board from a defunct Zoom H2. I >>>> would like to wire these and use as external mics for a working H2, but >>>> need wire. I'm trying to capture some bird songs emanating from trees >>>> on my property and want to try strategically placing this small board in >>>> areas of the trees where I've seen the birds.

If you are thinking of mounting the mics on a board, be aware that the >>> proximity of the board will badly affect the frequency response and the >>> directinal properties. Either drill a lot of holes in the board or
attach the mics to something perforated such as expanded metal mesh or a >>> sieve. Better still, attach them to a plastic-coated coat-hanger which >>> can be bent to get them in the right position. (The plastic coating
will damp down any reonances in the stiff wire.)

Thanks for the tip. Actually, I was just going to leave them on the
board with no attachments but I hadn't thought of mounting them in the
tree yet. The plastic coat hanger sounds like a great idea, however.

Wire length would be up
to 30 feet. For now, I'm not going to power the electrets separately >>>> and just use the output from the Zoom, just to keep things simple. Mic >>>> wire recommendations would be appreciated, and something that won't
break the bank. The wire will not be left outdoors all the time, only >>>> when I'm attempting a capture session.

The impedance of a circuit like that would be about 600 ohms, so it can >>> tolerate quite a bit of capacitance before you start to lose the high
frequencies. At 20 Kc/s a parallel capacitance of 13 nanofarads would >>> be needed to give 3dB loss.

The cheapest screened Ethernet cable is about 53 picofarads per metre, >>> so your 10 metre length would have nowhere near the capacitance that
might cause problems. The loop resistance will also be insignificant
compared with the 600 ohm microphone, so voltage loss will be negligible >>> too.

The cable has four cores which can be connected for stereo if you aren't >>> worried about a bit of cross-talk. If you need low cross talk - or if >>> there is a lot of electrical interference - two cables can be use, each >>> wired as starquad. If you find you are picking up radio stations, wnd a >>> few turns of the cable around a ferrite core immediately adjacent to the >>> recorder.

I have used ordinary house-wiring multicore telephone cable for this in >>> the past, with no screen at all, and the results have been perfectly
acceptable. If you can't get any cheap screened Ethernet cable, try the >>> unscreened type and see what happens.

If you are lucky, a computer systems installer might let you raid his
scrap bin and you could get a couple of 10-metre lengths of Ethernet
cable for free.

Actually I have about 10,000 feet of unscreened 4 conductor Ethernet
cable I picked up at a yard sale some years back. I've used pieces here >> and there for a variety of things, but mainly separated out the twisted
pairs and used as a radial ground screen for an antenna I built some
years ago. Cheap and worked great. I never thought of using them as
mic wire since they lacked the screen, but will give it a try first.
Thanks for mentioning this option!

That sounds very promising and it will cost you nothing to experiment a bit. If you use two separate runs, wired as starquad, and wind them a
few turns through a toriod or two, I would be very surprised if you find any problems.

Thanks, Liz. Sorry I didn't respond sooner, but I am not familiar with "starquad" and would appreciate exactly how this is set up. It needs
two runs of the 4 conductor Ethernet cable? Also, any particular
ferrite? Snap together type or toroid?

If you imagine you have cut cleanly through a four-core cable so that
you have a cross-section with the cores visible. Now rotate it so that
one of the cores is at the top - so, for convenience, we can refer to
the cores as North, South, East and West (the points of a four-pointed
star). One wire of the microphone circuit is connected to both the
North and the South core, so they run in parallel. The other wire is
connected to the East and West cores in parallel.

In practical terms, the North and South cores are soldered together onto
one pin of the plug (or socket) at each end of the cable. Similarly,
the East and West cores are soldered together onto the other pin at
each end.

Now consider where the current is flowing: in the N+S circuit, the two conductors will be sharing the current equally, so it will appear that
there is an imaginary conductor half way between them carrying the whole current. Similarly in the E+W circuit, the imaginary conductor will be
half way between them.

But - magic! - in starquadded cable the two imaginary conductors are in
exactly the same place in the middle of the imaginary 'star' - but the
currents are flowing in opposite directions, so the overall current seen
from outside the cable is zero. In reverse, any magnetically-induced interference in one conductor will be exactly equal and opposite to the
the interference in the other conductor, so if the circuit is properly
balanced there wil be no interference induced.

This is better than ordinary twisted wire in a situation where the
interfering fields are locallised. If only a short length of twisted
cable is exposed to an interfering magnetic field, (such as where a
microphone cable crosses a thyristor-controlled lighting cable) the
induced current may not be exactly equal in all the twists and may not
cancel.

This does not help with capacitively-coupled interference, which is best intercepted with screening. On a low impedance circuit,
magnetically-coupled interference predominates; on a high impedance
circuit, capacitively-couple interference predominates. Your circuit is
fairly low impedance, which is why I hoped you would be able to manage
without screening.

Either a clip-on or a toroid type of ferrite core should do the job; the
grade of ferrite sold for interference suppression, rather than radio
aerial baluns or R.F. transformers. I used a stack of several toriods
with about 5 turns of cable through the whole stack when I had to hang a
mic in the lighting gallery alongside killowatts of thyristor-controlled tungsten lamps.


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

---
* Origin: rbb pygate - the fidonet nntp junction (2:221/10.0)