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seth

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Apr 28 17 9:29 AM

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Is there any reason not to use microphone cable with the two conductors tied together as a 1/4" to 1/4" unbalanced guitar cable? I like the flexibility of Gotham mic cable, but are the any electrical characterictics that would make it a bad match if guitars are high impedance and mics are low impedance?

Thanks!
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soapfoot

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Apr 28 17 9:35 AM

I've seen it done.

There's even a small cult of people who like to use the two conductors as "tip" and "sleeve," and then tie the shield to the sleeve only at one end-- and mark that end, and ALWAYS connect it to the amp (i.e. cable only used one way).

They insist it sounds better for some voodoo reason or other that I never tried to understand, only because regular single-conductor shielded always worked fine for me!

brad allen williams

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seth

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Apr 28 17 9:43 AM

Hmm, that's interesting Brad. Have to try that. I like the Canare guitar cable myself, though George L has always sounded good to me as well.

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jesse decarlo

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Apr 28 17 10:10 AM

Doesn't it seem like a mic cable with both conductors wired together would have a slightly higher capacitance per unit length than instrument cable, because the mic conductors are twisted?

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soapfoot

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Apr 28 17 11:44 AM

jesse decarlo wrote:
Doesn't it seem like a mic cable with both conductors wired together would have a slightly higher capacitance per unit length than instrument cable, because the mic conductors are twisted?

No-- think about it like this:

Two twisted, insulated wires twisted together... versus one insulated conductor completely surrounded by a braided shield. 

The latter will most likely have far greater capacitance. I think. Let me look up some datasheets
 

brad allen williams

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soapfoot

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Apr 28 17 11:52 AM

mogami 2791 mic cable has 3.1 pF per foot between the two conductors, and 26 pF per foot between either conductor and shield.

mogami 2524 bulk instrument cable (a rather low-capacitance cable, in the grand scheme) has 39.7 pF per foot between conductor and shield.

canare GS-6 (my preferred choice) has 48.8 pF/ft between conductor and shield (I don't mind a little extra capcitance; slightly darker than Mogami, but I like).

George L has 20.4 pF/ft, so even this ultra-low capacitance instrument cable has almost 7x the capacitance between conductor and shield of the two conductors in the Mogami mic cable.

brad allen williams

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jesse decarlo

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Apr 28 17 12:03 PM

soapfoot wrote:
mogami 2791 mic cable has 3.1 pF per foot between the two conductors, and 26 pF per foot between either conductor and shield.

mogami 2524 bulk instrument cable (a rather low-capacitance cable, in the grand scheme) has 39.7 pF per foot between conductor and shield.

canare GS-6 (my preferred choice) has 48.8 pF/ft between conductor and shield (I don't mind a little extra capcitance; slightly darker than Mogami, but I like).

George L has 20.4 pF/ft, so even this ultra-low capacitance instrument cable has almost 7x the capacitance between conductor and shield of the two conductors in the Mogami mic cable.

Interesting!

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zmix

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Apr 28 17 12:22 PM

This is an interesting question.. and I love all the 'mythbusting".

I recently dug up a number of "experimental" guitar cables I made, and I listened to them again.

There are many factors that determine if the cable will affect the tone, most importantly is probably the inductance of the pickup... I measured the impedance of a standard "PAF" style humbucker and found that it peaked around 3.6kHz, where it was around 160kΩ.   This means that the resistance of the pots and capacitance of the cable are going to have the most influence above 3,600Hz. Though the pickup rolled off significantly above that resonant peak, so this will also minimize differences in cables, etc..

Of all the cables I tried the "best" sounding was one I made of stranded coax "video" cable, which had a braided shield as well. No markings on the jacket, I'm afraid..!!

Last Edited By: zmix Apr 28 17 12:30 PM. Edited 1 time.

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soapfoot

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Apr 28 17 1:06 PM

we should also say that most of these factors become negligible at low impedances, so for active pickups, none of this would matter much (as a generalization)

brad allen williams

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dcollins

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Apr 28 17 7:56 PM

I've heard the practical limit is around 20pF/ft from conductor to ground. Despite marketing capacitance claims. Oscilloscope cables might be even lower but are fragile. Everyone always likes the George L and it's pretty small.

 davecollinsmastering.com


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soapfoot

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Apr 28 17 10:55 PM

I used George L for some time. The straight plugs can be OK.

The right angle plugs are a little fiddly, IMO/IME. Easy to repair, but (like most solderless connectors I've experienced) fail more often than a good old-fashioned soldered connector.

I've never tried to buy bulk George L and solder conventional connectors on it; I suppose that's likely possible.

The kicker is, I don't prefer the bright sound of the George L, with the higher resonant peak, even if it DOES mean I get to "keep" more top end.

The "thing" everyone says is "why don't you just use the cable that lets you keep most of your signal, and then you can EQ away any top end you don't want/move the resonant peak with your tone control."

In theory that's all well in good; in practice that's just not how I roll. I like to simplify. I'm happy with the way the Canare works in my systems, so I just keep using it. To tell the truth, I NEVER think about cable (except if I have to assemble one), and I think that's the way I like it.

brad allen williams

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zmix

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#13 [url]

Apr 29 17 12:06 PM

scullyfan wrote:
Chuck, can you tell if the coax is RG59 or RG6 by any chance?

I am not sure, it's not solid core wire, though I think they make RG59 in a stranded core, braided shield, no foil, clear inner insulation, tinned copper shield and conductor.

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gold

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Apr 29 17 3:27 PM

I use RG58 for almost all unbalanced audio connections. If I have control over connector type I use BNC. For guitar cables I've always used RG59 because it's a larger diameter and more robust. RG6 I believe is even thicker but I've never used it for a guitar cable. I think I have 25ft of it somewhere and the right BNC's for it. It's too thick for general use for me.

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gold

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Apr 29 17 3:39 PM

soapfoot wrote:
There's even a small cult of people who like to use the two conductors as "tip" and "sleeve," and then tie the shield to the sleeve only at one end-- and mark that end, and ALWAYS connect it to the amp (i.e. cable only used one way).

They insist it sounds better for some voodoo reason or other that I never tried to understand, only because regular single-conductor shielded always worked fine for me!

 
There is a solid technical reason for this. I couldn't tell you if it makes a difference in this case or not. First you have to conceptually make 0V Audio Common separate from Shield. In a complex system like a console this helps. Neumann used this technique in their consoles. The idea is to keep 0V audio common as clean as possible. The best way to do it is to have Audio Common and Shield connect only at the power inlet. That way the shield noise goes straight to ground and doesn't contamonate Audio Common. I did that on my console even though all audio inputs and outputs are balanced. I ran separate 0V and Shield wires to each chassis.

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gold

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#16 [url]

Apr 29 17 3:46 PM

It strikes me just like a phono input the guitar input was designed more for cost than for best performance. Since a pickup is a coil it is natuarally balanced. If lower noise is a worthy goal then run the signal down twisted pair into a steup transformer then into the amp input. I bet you knock 20-40dB from the noisefloor. 

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soapfoot

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#17 [url]

Apr 29 17 10:17 PM

The low impedance output of the Les Paul Signature, Les Paul Recording, etc. may have done something like that. It never really caught on

brad allen williams

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zmix

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#18 [url]

Apr 30 17 7:09 AM

gold wrote:
It strikes me just like a phono input the guitar input was designed more for cost than for best performance. Since a pickup is a coil it is natuarally balanced. If lower noise is a worthy goal then run the signal down twisted pair into a steup transformer then into the amp input. I bet you knock 20-40dB from the noisefloor. 

Most of the noise in a guitar pickup is due to EM interference picked up by the coil itself, so in order to reduce noise you would need to use a pair of differential coils with opposing magnetic fields (aka a Humbucking Pickup).  You wouldn't gain anything by using a balanced output itself.

I built a Bass Guitar and incorporated a DI transformer and XLR output into the design,  I powered the internal electronics from the phantom supply, too!
It wasn't any quieter than the normal 1/4" "unbalanced" output.

Les Paul's personal guitar (for a time) used low impedance pickups (~600Ω) because he observed that all of the telephone equipment and all of his recording gear operated with a 600Ω impedance.
He did that for "fidelity" reasons, however, not noise.   Gibson finally offered that setup in their Les Paul Recording Model Guitar in the 1970s
It featured a "low-z" output and a hi-z output , via a step up transformer for use with a normal guitar amp:

LPrecordingdiagram.jpg

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Mike Rivers

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Apr 30 17 8:38 AM

gold wrote:
I use RG58 for almost all unbalanced audio connections. If I have control over connector type I use BNC. For guitar cables I've always used RG59 because it's a larger diameter and more robust.
 


I think using BNC connectors on a guitar and amplifier is a great idea. The connector makes the ground/shield connection the signal connection so you can connect and disconnect them without a blast of hum. And besides, it will frustrate anyone who steals your guitar. 

As an aside, proper patchbay plugs and jacks (as opposed to "phone" plugs) are made with the tip and ring slightly smaller in diameter than the sleeve, so when you insert the plug, the first part to make electrical contact is the shield. XLRs are also like this, with pin 1 being slightly longer than the other pins so shield contact is made first.
 



For a good time, call mikeriversaudio.wordpress.com

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gold

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#20 [url]

Apr 30 17 1:15 PM

zmix wrote:

Most of the noise in a guitar pickup is due to EM interference picked up by the coil itself, so in order to reduce noise you would need to use a pair of differential coils with opposing magnetic fields (aka a Humbucking Pickup).  You wouldn't gain anything by using a balanced output itself.



 

 
That makes sense. Oh well.

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