microphone cable

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I have a desk microphone without the cable.  I need to put on a cable  
that is just a center conductor and shield.  It will be about 3 to 4  
feet long.  

This is a crystal mic going into a tube amplifier.  As this is high  
impedance, is there a special mic cable ,or can I just use some rg58 or  
rg 8x cable  without degrading the audio.  It is only for communications  
quality speech.

I know all about RF type cable, but have not ventured into the audio.

Re: microphone cable

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I think RG cable is more than adequate for audio use, maybe "too good"!  
It may not be as flexible as you would like.


Re: microphone cable

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For that short a distance, and for speech-quality audio, I agree on
both points.  The flexibility of the cable may be an issue, although
since it's a desk microphone that may be less of a problem.

If you do want to optimize... professional microphone cables are often
designed with low capacitance per foot (to minimize the degree to
which the cable's shunt capacitance loads down the mic element and
affects the frequency response) and low amounts of triboelectric
effect (so that bending the cable doesn't generated voltages inside
the insulation which are then transferred to the conductors - this can
cause crackling or other noises in the audio).

Most of the big cable manufacturers (Belden, Mogami, etc.) make cable
of this sort.  Markertek sells it, but only in bulk quantities :-(

Ralph, if you want to experiment... I have a whole bunch of fancy
mil-spec cable sitting in my garage from a previous project / sideline
business... it's stuff like Belden 83318E.  I've got some fairly thin
one- and two-conductor (plus braided shield) that might work for
you... it's not as flexible as rubber- or PFC-insulated of the same
diameter but is definitely more flexible than RG-58 or RG-8x. I've
used it for line-level audio wiring in my stereo setup, among other
things.  Email me directly, send me a mailing address, and I'll post
you a long enough piece to try with your microphone.

Re: microphone cable
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Thanks for the offer on the cable.  I don't think it is worth it to do  
any experimenting with.  This is for a D104 Crystal mic that is going  
into an old Johnson Viking 2 transmitter . The audio quality on them is  
not all that great from what I understand. That transmitter is set up  
for just a center conductor and outer shield.   An audio plug similar to  
a pl259 with the center pin just flush with the connector.  Forgot what  
they are called.

I did not think it would matter in this case what kind of cable I used  
if it did not pick up AC hum or RF as it is only going to be 3 or 4 feet  
long.  Just wanted to run it by some that might have had tried it and  
ran into an unknown problem.

I have several kinds of small rg coax around.  Where I am going to use  
the mic , the wire does not have to be very flexable.  

Now If I really wanted the best, I would get one of those $ 100 AC cords  
that is oxygen free, some Monster mic cable and suck out all the solder  
connections in the rig and re do it with some of the Wester Electric  

Re: microphone cable
On Wednesday, 22 August 2018 22:00:15 UTC+1, Ralph Mowery  wrote:
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Just use a cable with a good screen density, not some old tv cable with just a vague notional outer screening copper.

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can't imagine why that would be best.

Crystal is never going to get you decent sound anyway.


Re: microphone cable
On 8/22/18 4:00 PM, Ralph Mowery wrote:
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Only if you've been listening to the "broadcast quality" AM guys.
The D104 tends to accentuate the highs.

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They are called an Amphenol connectors.
By the way, if you want to do the PTT upgrade, that Mic connector
is mounted in a 3/8" hole, so a standard 1/4" TRS jack will fit.

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Actually, it makes a lot of difference. The audio input on the
Viking is a vacuum tube grid. And the D104 is a high impedance.
As such you want to use low capacitance cable. RG-- is not low

"I am a river to my people."
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Re: microphone cable
snipped-for-privacy@att.net says...
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I wanted ot call it an Amphenol connector, but that is also a company  
that makes many types of connectors.  Maybe that is just a common name  
for that type of connector ?

I sort of thought about doing the PTT upgrade as I have the factory mod  
information for that, but think for now I will stay with the plate  
toggle switch as the D104 I have is just a stand and not the one with  
the 'grip to talk' switch.I may make the mod if I get a PTT mic and put  
the Viking on the bench.  I just picked the Viking up about a month ago  
and put together a station with a Hammurlaud 140 receiver to make it a  
station of about the time I was born.


Re: microphone cable

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You have a point, but is the higher capacitance enough to matter for a  
relatively short cable?

Also, has the D104 crystal element held up over time?  My recollection  
of microphones back in the 50s, was that a crystal element eventually  
"dissolves" in normal humidity.  The D104C ceramic version was supposed  
to overcome that problem.


Re: microphone cable
snipped-for-privacy@aol.com says...
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My  mic could have either a crystal or the ceramic element, I am not  
sure which.  Like you mentioned, the crystal elements often did not hold  
up very well.  Hard telling how old this one is as it was given to my by  
a friend that got it from a long gone ham.

Four feet of the rg 58 type cable has about 120 to 150 pf of  
capacitance.  There is 300 to 500 pf connected directly across the mic  
input of the transmitter inside at the mic connector.

Again this is not hifi and 20 or 50 feet of cable where I am sure it  
would make a difference.

Re: microphone cable
On 8/23/18 12:06 PM, Ralph Mowery wrote:
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As in everything in life, you can make an attempt to do things the
right way, or you can just say "fuck it, close enough."

You asked if there was a difference and I said that there was and

"I am a river to my people."
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Re: microphone cable
On Wed, 22 Aug 2018 12:54:50 -0400, Ralph Mowery

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You can buy a cheap 6 foot guitar cable on ebay for under $5. Cut off
the 1/4" jacks and install your own connectors. A local music store may
even have an old used guitar cord and sell it real cheap.  

Re: microphone cable
snipped-for-privacy@tubes.com says...
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That is just about what I did.  I got on ebay and bought a 50 foot cord  
for about $ 12 and plan on cutting off the ends.  I will see how that  
works out when it comes in in a few days.

I thought I had some rg58 with the stranded center, but could not find  
any.  Could not use the 8x as found out it was too large to fit the  
hole.  I have some of the rg 142  think that is it, double shieled  
silver plated size as 58) but did not want to use that cable at a couple  
of bucks per foot and is sort of stiff.  

Re: microphone cable
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75 ohm type would have less capacitance. Ideally you want 3 wire line.
Ground common and hot. The D104 has rising peak 2-3 kHz and they sounded
very intelligible to me, in fact others try to duplicate, either with
electronics or other mikes with similar response. Guitar cable should also
do fine.


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