Where get short length of fine enamelled wire in UK?

[Karen]

Where can I get a small spool of fne enamalled copper wire? I'm in
the UK and want about 25metres of single strand of enamelled wire.

Most big dealers sell no less than 250g/8 oz but that's way too long
for me! These are the sort of diameters.

SWG 40 (.0048) = 36or37 AWG
SWG 38 (.0060) = 34or34 AWG
SWG 36 (.0076) = 32or33 AWG big thick

The wire is for a body-worn covert mic and the wire will be twisted
into a par.

A light-brown low-gloss outer would be ideal for camouflaging the wire
but I suspect it doesn't exist. :-(

 

[Karen]

eBay might work. I've found it good for small and unusual finds.
Better, for this, might be salvaged relays, solenoids and small
AC or DC motors, tape head demagnetisers... any kind of
electromagnet coil. Colours vary more than you'll likely find in
commercial outlets. I've even seen dark blue, but never seen it
on sale. Salvage is good though, you'll find a wide range of
colours similar to human hair colours, some too bright but some
near ideal. And free, and in useful amounts. A small hacksaw, a
screwdriver, and a pair of pliers, might be all the tools you
need to get at them. Getting a look at them is even easier.

I'm not really happy about eBay. Salvage might be good but I worry
that I am getting wire with resistence from some transformer.

 

[Karen]

:Where can I get a small spool of fne enamalled copper wire? I'm
:in the UK and want about 25metres of single strand of enamelled
:wire.
:
:Most big dealers sell no less than 250g/8 oz but that's way too
:long for me! These are the sort of diameters.
:
:SWG 40 (.0048) = 36or37 AWG
:SWG 38 (.0060) = 34or34 AWG
:SWG 36 (.0076) = 32or33 AWG big thick
:
:The wire is for a body-worn covert mic and the wire will be
:twisted into a par.
:
:A light-brown low-gloss outer would be ideal for camouflaging the
:wire but I suspect it doesn't exist. :-(


So how do you twist 0.0048" wires into a pair without breaking
it? Even when you do manage it, how do you stop the twisted pair
from breaking due to snagging on clothing while being worn?

Twisting a pair of SWG 40 wires is not so hard at all. Try it. They
are only a metre long.

You can stick the twisted pair to a garment or to skin every 6 to 8
inches. You can even us a small stitch on a garment of about 3mm
(each wire done separately in a needle). Trouble is the small 3mm
visible section sparkles too much and would be noticed.

If it the wires break when they're removed then that's no big deal
because they can be replaced.

My thinking is that it's a good thing if the pair break relatively
easily. You might get challenged with a question if "that" is a
mic, and in response you could then pull it away, breaking the
wires and display it is unattached. It's not foolproof but might be
better than having no reply.

Anyway, I'm looking for a source that doesn't sell me over a mile
of the stuff in a 250 grams reel.

 

[Ross Herbert]

:Where can I get a small spool of fne enamalled copper wire? I'm in
:the UK and want about 25metres of single strand of enamelled wire.
:
:Most big dealers sell no less than 250g/8 oz but that's way too long
:for me! These are the sort of diameters.
:
:SWG 40 (.0048) = 36or37 AWG
:SWG 38 (.0060) = 34or34 AWG
:SWG 36 (.0076) = 32or33 AWG big thick
:
:The wire is for a body-worn covert mic and the wire will be twisted
:into a par.
:
:A light-brown low-gloss outer would be ideal for camouflaging the wire
:but I suspect it doesn't exist. :-(


So how do you twist 0.0048" wires into a pair without breaking it? Even when you
do manage it, how do you stop the twisted pair from breaking due to snagging on
clothing while being worn?

 

[Karen]

It's copper. How much resistance can there be? it will be
fine. Whatever source of copper wire you use, there will be some
resistance, but not enough to be a problem. More important is to
use a balanced line input, i.e. a differential amplifier, so
noise picked up on the twisted pair will cancel, leaving the
sound signal you want intact.

What I meant was that a transformer may have an impedance of 50K and I
don't want that wire because I assume the wire is made in a way to
give extra resistence.

Good point about the two wires needing to be balanced. I remembered a
discussion which started by saying the twisted pair would have to be
balanced then someone else said try it without. I'll see what happens!

My recorder has unbalanced inputs and I would rather not get some
device to put between amp & mic.

 

[Karen]

once you have made the twisted pair, try getting some matt
varnish in a small brush and running the wire through the
bristles. Once it dries it will be less shiny, especially if you
draw it through a gently folded cloth while it's still tacky,
ideally the same cloth you'll be using, so any fibres that stick
to it will help camouflage it.

Oh! That is creative.

Not sure how easy it will be to leave a suitable film of varnish or if
the varnish can be flexed when dry but it has to be worth a try. I
wonder if soft-hold hair lacquer is another way to do this.

You seem to have a good feel for what I am trying to do. Have you got
experience of covert recording?

 

[David Chapman]

My offer to help is STILL available if you care to contact me
directly. I have some very thin TWO-core enamelled wire that will do
the job perfectly for you.

- Dave

 

[Karen]

My offer to help is STILL available if you care to contact me
directly. I have some very thin TWO-core enamelled wire that will do
the job perfectly for you.

- Dave

Hi Dave, sorry I didn't get back to you before. I wasn't sure you were
really serious about letting me have some wire.

Email sent.

K

 

[Karen]

What I meant was that a transformer may have an impedance of 50K
and I don't want that wire because I assume the wire is made in a
way to give extra resistence.

[trimmed]

Re balanced, try it WITH first. It's just as easy to build a
differential amp from op-amps as a single input type, you just
configure the resistors differently, and they're all standard
circuits. Unless your wires to the mic are less than about an inch
long, you really need that noise cancellation that a diff amp
gives.

Despite your recorder having only unbalanced inputs, you might get
away with it so long as you don't refer to any ground, only to the
chassis or local ground inside it. If you use an electret mic
(smaller than dynamic) the FET in it will put out a voltage high
enough to help with signal to noise ratio even over an unshielded
twisted pair. It won't be hi-fi but it will be useable. You can
remove constant noise later with a digital editor too (the kind
that take a noise print, so if you use one, record some noise on
its own as sample).

Hello Lostgallifreyan, your post contains a lot of info and much of it
intrigues me. Can I break into parts.

You say "it's just as easy to build a differential amp from op-amps as
a single input type, you just configure the resistors differently".
The mic capsule will be an electret and I was going experiment with (a)
an electret mic with two contacts and (b) an electret mic with three
contacts.

I was just going to put the mic capsule in place and run the two
twisted fine wires to the input of the recorder. In the case of the
three wire capsule I would add a resistor between 2 leads (as advised
by the manufacturer) to convert it to two wire operation.

I wasn't going to build any amplifier! This is a little bit out of my
depth. I was just going to plug the mic. However, now that you have
mentioned amps can you point me in the direction of a circuit or web
page which might show more detail of the sort of thing you mean.

I would like to avoid removing noise because when I have tried that
using an audio editor using a noise sample from a non-speaking part of
the recording, I found the speech quality suffered a bit too much.

As background, one particular three wire capsule I have in mind is the
micro-sized Knowles FG. http://tinyurl.com/bbdzg5 (I am in the UK.)

This FG-23329-P07 capsule is prewired with 3-wires (positive, negative,
output, and also a shield wire from the case. It is in the chart on
page 9 of Knowles's Design Guide:
<www.knowles.com/search/pdf/07-KA-895_designguide_final_v1.pdf>

Thank you or anyone else for any info.

K