connect telephone microphone to guitar pedal

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Hi all,

In the 1960's the band Fairport Convention kick-started UK electric
folk, and the fiddle player Dave Swarbrick is still a legend. His
fiddle sound was extremely distinctive and I have read that back in the
day, he used an accoustic fiddle amplified using a microphone from a
telephone.

In a bid to recreate his sound I bought an second hand old fashioned
telephone and took the microphone out. It then occured to me that
soldering the mike to a cable and plugging it into my mixing desk
probably isn't going to cut the mustard!

So I am wondering if anyone can recommend a circuit that would allow to
use a telephone microphone and produce the same sort of signal that,
for example, an electric guitar would, so that I could plug it through
my guitar effects pedal into an amp or mixing desk. I'm really not
bothered about excessive quality - the main point I suppose is to get
the level right and not have a stupid amount of noise. Preferrably the
minimum amount of components!

Thanks a lot for any advice,

Ben


Re: connect telephone microphone to guitar pedal



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the
to

Depending upon the vintage of the microphone, it may well be a carbon
granule based unit.  This means that it acts like a variable resistance
when sound wave pressure is applied.  This means you will need to pass a
continuous current thru the microphone and then convert the varying
current into a varying voltage.  Tell us the resistance of the
microphone.


Re: connect telephone microphone to guitar pedal


Hi Anthony,

thanks very much for the info. I measured the resistance of the
microphone and it varies a lot, between I would say about 200KOhms min,
and at max so high my metre thinks there is no connection. Does that
sound like a carbon granule unit? I think if it isn't, there is no
point in me trying this experiment because I'm pretty sure Swarbrick
would have used one of those. I have looked on the telephone for
markings which might reveal its age but I can't find much... it just
looks like a classic 70s telephone. Any ideas for what next?

Cheers,

Ben


Re: connect telephone microphone to guitar pedal



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You can tell if it's a carbon element by inspection. Carbon elements
are about the diameter of a quarter or half-dollar, and almost 1/4"
thick. The front is domed, with fairly large holes, and on the back
there's a center contact like a mongo "D-cell"-type contact, and a
ring around it like a slip ring. If you shake it while holding it up
to your ear, you can hear the carbon particles rattle around in the
chamber.

If it's a little tin cannister about the size of a pencil eraser, with two
leads coming out of it, it's not a carbon mic, but probably easier to use. ;-)

Hope This Helps!
Rich


Re: connect telephone microphone to guitar pedal


It does help, Rich, it's definitely a carbone mike according to that...

Any ideas for a circuit then?

Cheers,

Ben


Re: connect telephone microphone to guitar pedal



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Well, a carbon mic needs a current going through it - the sound
compresses and releases the carbon particles, so the resistance
changes. I suppose you could take a 1.5V battery or wall wart,
and pick some handy current - like, put about a 600 ohm resistor
in series with it, with a 1K or so pot, and the mic., all in
series with the battery.
                                      +
. Batt + o-+- 1K pot --- 600R ---+---- CAP ----o Signal
.          `----^                |
.                               MIC              To Line In
.                                |
. Batt - o-----------------------+-------------o Gnd

Try maybe a 10 uF cap, with the positive to the mic, and the
negative to the input. The mic. shouldn't be polar, but just for
the sake of style, I'd connect the ring to the negative and the
center contact to the R/C junction.

I don't know how long the battery will last with this setup,
but a wall wart would last forever. ;-)

I haven't built, simulated, or even tried this, so all of the
standard disclaimers apply: you assume all risks, there are no
guarantees, etc.

Have Fun!
Rich


Re: connect telephone microphone to guitar pedal


Thanks a lot Rich! I'll give it a go and report on the results...

Cheers,

Ben


Re: connect telephone microphone to guitar pedal


Right, I tried it, and it worked! It sounds very distorted though. I
don't think it is seriously useable as it is very feedback prone, but I
had fun making it work.

Here is a copy of the post I just made on fiddleforum.org.

Now I know I'm not the only one here who regards Dave Swarbrick as
something of a hero... he seems to have starting the ball rolling when
it comes to the amplified fiddle in english folk. Not only his playing
but also his sound on the early Fairport Convention records has a
certain something that I have always wondered what it was. I read in
several places that he used a telephone microphone to amplify his
fiddle back then.

I decided seeing as I can't play like him but I can just about handle a
soldering iron, I would try a little experiment. After a trip to the
second hand shop for an antique telephone with a carbon granule mic,
and a trip to usenet for some advice on a circuit to connect the thing
to my mixer (http://tinyurl.com/nnvg3 ), I produced this:
http://www.benkenward.com/telephone_fiddle.mp3 .

I warn you it's not pretty. I can't decide if it sounds like anything
other than a really distorted recording on a rubbish mike. It might be
surprising if it did seeing as that's what it is... But, I don't know,
something in me is almost saying there might be just a hint of that old
Swarbrick sound. Just my imagination?

Please no comments on the playing, after arsing around with making the
circuit all evening I had a rushed minute left to actually record
something before neighbour imposed curfew!

Cheers,

Ben


Re: connect telephone microphone to guitar pedal



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...

Aw, shucks! This is just a link to the _advice_! How about a link to
the _mixer_! :-)

 I produced this:
Quoted text here. Click to load it

And yeah - I haven't bothered to configure sound yet on this box, but
again, I was hoping for a picture of your carbon mic duct-taped to
your fiddle. ;-)

Cheers!
Rich


Re: connect telephone microphone to guitar pedal




Rich Grise wrote:

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They also rattle.

Graham


Re: connect telephone microphone to guitar pedal



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I might be able to tell you how but I just got a phone call from the people
down your local and they said that your folk band is shite and amplification
would make you sound louder but you would still be shite and, by the way,
why don't you just fuck off and stop coming down the pub to inflict your
shite upon us. We just tolerate you because Ted smiles a bit but, in case
you haven't noticed, Ted is senile.... Oh, you wouldn't have noticed because
you are as well. Anyway, we've bought Ted an MP3 player so you're not needed
anymore.

DNA



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