Quad mic cable and capacitance

[p0llen_p0ny]

I recently purchased a bunch of Mogami quad mic cables since I heard they cut back on RFI. Then I read about capacitance. Is it that detrimental to the sound? Should I sell off my quad cables and go with the standard kind?

[tele_player]

Originally Posted by p0llen_p0ny

I recently purchased a bunch of Mogami quad mic cables since I heard they cut back on RFI. Then I read about capacitance. Is it that detrimental to the sound? Should I sell off my quad cables and go with the standard kind?

The capacitance creates a small high frequency roll-off whose cutoff frequency varies with the length of the cable. Compare a quad cable against a lower-capacitance cable of equal length to see if it matters to you.

[patch]

Originally Posted by tele_player

The capacitance creates a small high frequency roll-off whose cutoff frequency varies with the length of the cable. Compare a quad cable against a lower-capacitance cable of equal length to see if it matters to you.

I'd like to know the answer to this question too. How much high end roll off are we talking? What lengths do you think would start to be noticable?

[squeegybug]

Gotham's quad cable is actually lower capacitance than their standard cable. But listening (along with noise suppression, if you need that) is what counts. I tested a bunch of quad cables from Gotham, Mogami, Canare, against many standard 2- and 3-wire versions and the quads mostly sounded a little softer, with less bass and treble clarity... subjective... These were all 20' cables.

If you've got of a bunch of money invested and everything already wired up, may not be worth it to you to switch now, but as mentioned you can always take a listen to alternatives to find out how sensitive your system is to the cable effects.

Steve

[ProPower]

Mogami quad cable (P/N 2534) capacitance is 33.6 pF/ft (wired in balanced quad configuration). Assuming a 150 Ohm output impedance from the microphone, a 10 foot length of cable and a 1.5KOhm input impedance to your preamp you get a simple RC circuit with a 20dB/decade rolloff at 1/(2*3.14*R*C). R in this case is the parallel combination of R_mic and R_preamp = (150 * 1,500)/(150 + 1500) = 136 Ohms. The -3dB point for a 10 foot cable is 3.48MHz. Be aware that phase shift starts a decade before this so at 348kHz there is the beginnings of phase shift in this cable. Extending this further a 100 ft cable would have a -3dB point at 348kHz with the beginings of phaase shift at 34.8kHz.

IMO a 20ft. or even 40ft. one of these cables should be quite capable for 44.1K or 48K work. If you are a 192K sampling guy then having cable BW around 5X of 192K seems like a reasonable choice.

-Lee

[DavidJ]

Lee,

I’m a bit confused as to what digital sampling rates have to do with an analog microphone cable. It would seem to me that a 20-20k bandwidth (or better) should be his primary concern, since it’s simply connecting an analog microphone to an analog preamp. According to your calculations, that doesn’t appear to be a concern. Am I missing something?

[ProPower]

Hey there,

No, your not missing anything except maybe that -3dB (Bandwidth) is one thing and phase shift is another. Phase shift begins 1 decade below the -3dB point.

The reason to mention sampling rate is that if you are going to sample at let's say 96kHz, you probably wouldn't want any unwanted phase shift in your system from just the cabling. Putting the cable/mic/mic preamp system at 5X the sampling rate (which is 10X the Nyquist limit of that sampling rate (ie 10X = 1 decade)) means there is no phase shift (which starts 1 decade below the -3dB point of a simple RC circuit) being added at the nyquist limit of the system you are using. So for 96k sampling, using a cable/mic/micpre bandwidth of 480kHz gets you there. at 44.1k 220kHz gets you there. Be aware that there are 300 ohm dynamic mics as well. All the calculations I did so far assumed 150 Ohm for the mic.

(I guess Iassume everyone is recording digitally :-).... if you are using an analog tape deck then the same principals apply but you will have to decide what the bandwidth of the tape recording medium you are going for is).....

Note: all of this from a detached analytic POV. I make no claims about the relative audio quality (precieved or otherwise) of various cables :-)......

-Lee

[takman]

strong 5 year bump here...

the capacitance thing with the mogami 2534 cable is something i just became aware of...

from researching, people are saying that the 2534 cable can cause high frequency roll offs due to its higher capacitance.......BUT, they say under 20 ft. will not will not make a difference between the standard 2549 mogami mic cable...and the quad 2534...


all the cable in my studio is mogami 2534. BUT, no cable i have is over 12ft. long...

im going to be ordering some mogami cable from Redco, because i need to wire a bunch of mic cables for micing my drum kit......but now im thinking of just getting the standard 2549 mogami cable...

So then i would have a mixture of 2534 and 2549 cable on my drumset....should i use the 2549 on the higher frequency stuff like overheads and the 2534 on lower stuff, like kick..toms etc...

also thinking about using the 2549 on my monitors...

or is it not going to matter all? overthinking?

[takman]

interesting....on mogami's site for the 2549, it says this

This cable is recommended when extended high frequencies are important

[nosebleedaudio]

Originally Posted by takman

interesting....on mogami's site for the 2549, it says this

The cable length plays a huge part in this, it simply adds up..so if you need a 250' cable use 2549, a 15' ...I doubt most would notice..

A good mic pre & the Mic also plays a huge part in RFI..Have heard radio stations from both sources...the cable had NO affect..
Plus 2549 is far more rugged...IMHO.

[Bob Ross]

Originally Posted by takman

overthinking?

That'd be my vote...

[AlexDaCat]

A cable may be viewed as a cascaded low pass filter, wher the capacitance shunt is between cable and a series inductor + resistance, (the magnetic and resistive components of the wire)..

READ: Transmission line

[neirbod]

I thought about this a few years ago when deciding on cable for location sessions. I forget the details of the math, but my conclusion was for cables up to 100' it seemed any effect of quad cables was more theoretical than audible. This was based on Canare star quad specs.

[UPRYZ]

If anyone here does a reliable double blind test and can hear the difference between 20' quad vs regular i'll eat my pants.

[nosebleedaudio]

Originally Posted by UPRYZ

If anyone here does a reliable double blind test and can hear the difference between 20' quad vs regular i'll eat my pants.

what kind of pants?

[Aeolian]

My personal experience with some Canare is that it sounds great. But I mentioned it on PSW once and a bunch of folks who work at the varsity level jumped in about the capacitance. Maybe it's because they tend to work with several hundred feet at a time. Obviously
From the numbers it is marginal at best in a studio situation.

[UPRYZ]

Originally Posted by nosebleedaudio

what kind of pants?

Jeans, corduroy, kahkis, wool dress slacks, you name it

[AlexDaCat]

Originally Posted by neirbod

I thought about this a few years ago when deciding on cable for location sessions. I forget the details of the math, but my conclusion was for cables up to 100' it seemed any effect of quad cables was more theoretical than audible. This was based on Canare star quad specs.

Unless your system is RF, then good quality cable has no probs regarding Capacitance or large roll off in the audio range...