Microphone cables....

[ke7trp]

I discovered something on accident today. 

My mic cables where the low end house brand at Guitar center. These XLR cables connect my MXL large diaphram condensor mic to the mixer console and then to the Globe king 500 Mod deck.  These cables where $9 each.

I had clear sound that I was happy with.  I ran an audio gen into the Globe 500 and used the spectrum. My plot is 20hz flat out to 12,000. 

A friend came over and gave me some "old" mic cables.  These where half inch in diameter. I looked them up and they sold for $300 each!  THey are high end cables

I setup the monitor reciever and tested the system. I then installed the large heavy cables and WOW. It was like someone took a blanket off the microphone! 

In my research as to why this is happening.. I found that its recomended to use "balanced" and high quality mic cables with this type of microphone. It states this clearly in the manual to use a balanced cable. My old cables where coaxial style. The new high dollar cables are in fact balanced as it is written on the side of the cable.

I found you can get decent to high quality balanced mic cables for decent prices. I would never pay $300 for a cable.. But a good Mogami brand is only $60 in most cases. 

If you are unsure if your cables are balanced, You might want to check. The differerence in my station was dramatic on the mid to high end response. Maybe when I have some time, I will sweep the system again to see the gains. The midrange and high end is much much louder and clearer now.



Clark

[kc6mcw]

I have so many cables now to replace... thanks again Clark for costing me more money.

[w4bfs]

capacity per foot is still capacity per foot ... ostensibly, the larger cable has larger spacing and less capacity per foot to load the microphone mids and highs ... what is the mic output Z ?

[Tom WA3KLR]

What are the cable lengths?

[K1DEU]

Yes when RF blankets our first (sometimes later) audio stages we are not concious of what is happening. The transistor, tube or op amp is being re biased towards cutoff from the detected RF, dropping the gain and sometimes clipping the linear audio.

17 Years ago WA1HLR aptly pointed out to me that old oxidized woven shields do not shield RF.

Also brand new spiral shields are also worthless for RF shielding.

Do not be concerned about C per foot so much. Brand New RG-58 A/U stranded center, full woven braid is an excellent affordable option to new woven Audio cable, which is difficult to locate. 73  John

[ke7trp]

The mic is 200 ohm output according to the manual.  20 to 20K. 

The length of both cables is the same. About 4 to 5 ft. I would have to measure them to be sure. But they are the same length.

I tested this over the air tonight and people did not believe I was switching A mic cable out. They accused me of cranking the EQ up! 

Are you guys saying that the fact that the standard house brand mic cable is unbalanced and the large diam cable is balanced is not the reason? 


Clark

[w4bfs]

200 ohm output Z .... seems it should not be so sensitive to cap loading .... balanced audio is still the way to go ....
could be that John K1deu is on to a more likely source of the problem .... big ferrite bead on the cable time 73  John

[Ian VK3KRI]

Arn't those XLR mics Phantom powered?  For them to work you need a balanced cable + ground.  I would have assumed that any store-bought cable with XLRs on each end would be balanced.

Hmm , thinking some more, if you had XLR to XLR with pin1 (ground) connected, and say pin 2(hot) and the mic was a transformerless FET type condensor, the power feed would work, the mic would probably drive pin 2 and 3 out of phase  , but at the pre amp one input would be floating. The result would probably depend on the preamp design



                                                                                   Ian VK3KRI

[AB2EZ]

I agree with Ian and the other respondents:

Using a cable with only a center conductor and a shield, instead of a balanced cable will:

1. Result in up to a 6dB reduction in the level of the output of the amplifier, depending on the details of the microphone output circuitry and the amplifier input circuitry

2. Result in saturation (i.e. gain reduction and distortion) of the transformers (if transformers are present) that couple the phantom power to the circuitry in the microphone... because of the unbalanced currents flowing through the cable-facing sides of the transformers.

3. Make the microphone-to-amplifier link more susceptible to r.f.i. (differential mode)

Stu

[DMOD]

You don't need expensive cables for good audio. Here is an example: http://www.fullcompass.com/product/298701.html

Belden 1812, 1813, or similar cable with good XLR connectors (such as Neuman's) will give you good audio. 24 to 20 guage twisted pair wire with braid with at least 94% coverage is the norm.

In some cases, the Pin 1 shield needs to be connected to the connector shell, but left unconnected to the shell at the mixer. You may have to experiment.

Dynamic mikes don't need phantom power but most of the Marshall's I've used are condenser mikes requiring phantom power. I prefer the Marshall's with Fet circuitry and internal impedance matching output transformers. 

[/size]

My mic cables where the low end house brand at Guitar center. These XLR cables connect my MXL large diaphram condensor mic to the mixer console and then to the Globe king 500 Mod deck.  These cables where $9 each.

Are you saying you don't know if these were shielded, balanced cables?

[WBear2GCR]

What needs to be clarified is how you were connecting this condenser microphone originally, and how you were connecting it with the fancy "balanced" wire?

Was the first case a phone plug?
Was the second one a three pin XLR?

Is the microphone phantom powered?

Fwiw, the transformer in the mic will not be saturated if there is a cap internally in series with the transformer that prevents DC from flowing in the transformer (likely).

If the problem was actually RF getting in, the balanced cable might help if the CMRR of the input to the mic pre is any good at RF freqs - it's not always.

John, what do you mean by "spiral shields" are no good for RF? Do you mean spiral copper wire, or spiraled foil with or without braid over?? And if the latter, why?

                  _-_-bear

[kc2ifr]

Come on guys......this is NOT rocket science.........this is one of the best references on the web.....check it out...
http://www.rane.com/library.html

Bill

[W2NBC]

It's NOT "Monster Cable"..

It's copper to copper and varies as John DEU mentioned in shielding quality.. Here's an interesting treatment on Mic cabling:

http://www.dealamerica.com/pdf/Mic%20Cables.pdf

[kc2ifr]

Jeff,
Thanks for the post...........very interesting.
Bill

[W1GFH]

...20hz flat out to 12,000.

I then installed the large heavy cables and WOW.

The midrange and high end is much much louder and clearer now.

If your response was flat 20Hz-12K Hz to begin with, how can a new cable alter only selected frequencies? That don't sound right. (And I ain't buying new cables)

[K6JEK]

...
(And I ain't buying new cables)

Joe, I was recently given quite a collection of microphone cable in bright yellow, electric blue, road hazard orange, cherry red, all two conductor shielded, nice and flexible.

What color do you need?  What color shirt do you usually wear when transmitting?

[ke7trp]

I love it when engineers cant explain something.. They claim its not true!  LOL...

My point of the post was and still is simple.. You can have XLR to XLR cables in balanced and unbalanced configuration. My microphone requires a balanced cable. I was using an unbalanced XLR to XLR cable.  I had a huge difference in sound when switching to what the microphone required. \

Stu.. Thanks for posting. This must have been the issue I have. I have already found 2 other hams that had this same issue going on.. WHen they switched the balanced decent to high quality XLR cable they had more mic gain and more Mid to HIghs.

Thanks alot for the explination!

[W1GFH]

...
(And I ain't buying new cables)

Joe, I was recently given quite a collection of microphone cable in bright yellow, electric blue, road hazard orange, cherry red, all two conductor shielded, nice and flexible.

What color do you need?  What color shirt do you usually wear when transmitting?

Tis' not I who needs the cables, Jon. "Doth balanced cables give better mic audio response?" 'tis the discussion subject in yon forum. (And why am I talking in Shakesperian tones?)

[K6JEK]

...
(And I ain't buying new cables)

Joe, I was recently given quite a collection of microphone cable in bright yellow, electric blue, road hazard orange, cherry red, all two conductor shielded, nice and flexible.

What color do you need?  What color shirt do you usually wear when transmitting?

Tis' not I who needs the cables, Jon. "Doth balanced cables give better mic audio response?" 'tis the discussion subject in yon forum. (And why am I talking in Shakesperian tones?)

But think how sharp you'd look with a bright red microphone cable.

[WBear2GCR]

Orange - sophisticated AM ops use orange. Yellow too.

My mic cable is white "Teflon" ^{reg tm DuPont}, what the "good guys" use...

           

                       _-_-bear

[kc2ifr]

I use 22 gauge 2 conductor foil shielded Belden cable. Not designed for mic cable use but it works great.
And its gray

[ke7trp]

Mine is grey too!   

Clark

[Ian VK3KRI]

My point of the post was and still is simple.. You can have XLR to XLR cables in balanced and unbalanced configuration. My microphone requires a balanced cable. I was using an unbalanced XLR to XLR cable.  I had a huge difference in sound when switching to what the microphone required. \

Whats the wiring of that 'unbalanced XLR - XLR  is it:

Only two conductors used,

or is it one of the signal lines bonded to ground

Or something else?

I've only every seen such things as hacks for specific pieces of equipment - though its not as if I spend my life connecting bits of audio gear.

(Although I have seen a lot of XLR cables with the GROUND/SHIELD lifted at one end.)

                                                 Ian VL3KRI

[WD5JKO]

Clark,

    I'm interested in your situation. Since you changed from coaxial to balanced with shield, and went from dialectic X to dialectic Y, I am confused as to what did what to change your sound. Can you sketch some schematics of how you hooked the two cables up showing the difference in wiring?

What I am looking for is represented in the following link.
Check out Figures 15, 17, and 18:
http://zone.ni.com/devzone/cda/tut/p/id/3344

Since the input to a GK 500 is not balanced, I wonder how you hooked up that balanced cable.

Also when you swept the GK audio, as being flat from 20 hz to 12 Khz, I wonder how you did that, and what mods have you done to the GK audio chain?  To be flat over that large of a band, the -3db points must be considerably wider, say at least 10 hz to 24 Khz. Even if the audio was perfectly flat over that frequency band, the RF linearity of the 4-400 RF PA tube with a passively modulated screen grid would likely have issues with the frequency extremes. I also doubt that the modulation transformer would behave well over that wide of a frequency band.

The subject of super cables versus cheap cables is similar to solid state audio versus tube audio. Sometimes claims are valid, and at other times snake oil salesman capitalize on a theory blown out of proportion. Here is one such exchange that is interesting to me regarding audio cables:

http://www.audioholics.com/education/frequently-asked-questions/audioquest-cable-theories-exposed

 I think you stumbled upon a good thing Clark. I am not trying to discredit anything you have said. Instead I am hoping that you can help me understand what you did, so that I and the group can benefit from this.

Regards,
Jim
WD5JKO

[ke7trp]

John,  Thanks for being open minded.

I was only changing the cable from the micophone (large diam condensor MXL) to the Mixing console/preamp. 

The Mixing console outputs to the Globe king 500C mod deck via the phone patch jack.  I use an impedance matching transformer at the rear of the globe 500C. The reason for the transformer is that this particiular mixing console outputs low impedance only on both XLR and TR/TRS jacks.

I was going from a cheap Guitar center cable at the mic to an expensive(but free to me!) cable.

The Globe king 500C modulator deck is reworked by Robert W0vmc.  Its his design that I installed.  The Phone patch jack now feeds the second AMp stage.

The 4-400 was rewored with different and large bypass caps ect.. ect ect..

I swept the radio by inputing an Audio sweep of 20 to 20,000hz into the mixing console. I then recieved the sweep on my reference reciever that feeds the Spectrum.

This produces plots of the mixing console and globe 500C.   This plot is about flat from 20, all the way up to 12,000 where it rolls off.  Its within a DB or so most of the way. I think the limitation is the iron to get past 12,000. It certainly goes low.

Why the cable workes better for me is the discussion.  But I am ok with no explination.  I know that when I switch the mic cable both bads of AMers all told me that there was a large difference in tone and sound. The mixing console shows more output and in fact will light the clip light unless I back the gains down with the large cable. 

Clark