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running two mic cables together?
Old 17th May 2003
  #1
Lives for gear
 
2 Reviews written
🎧 15 years
running two mic cables together?

For reasons too long to get into, I'm planning on running two mic xlr cable in between my ATM 25 and Neve preamp for kick drum micing. Has to do with ease of patching and unpatching since I use my Neve on quite a bit of things. Will the sound be affected since the preamp is transformer based? Each cable is 20'.
Old 17th May 2003
  #2
Moderator
 
Tim Farrant's Avatar
 
🎧 15 years
From my experience, cable length can affect some devices more than others. A transformerless mic for example is less likely to be effected by the cable capacitance than one with a transformer output. My advice is to use cable with a low capacitance spec, which is usually given a pF per metre (or foot).

Avoid using star quad cable as this generally has a higher capacitance between legs.

Sommer (Germany brand) make some real nice cable, much cheaper than Mogami. Check out the Sommer Galileo, very low capacitance and OFC.

I imagine the effect of the mic output to Neve input interaction will swamp any effects of the cable to Neve interaction - if you can understand what I mean !!

Cheers
Tim
Buzz Audio
Old 17th May 2003
  #3
Gear Maniac
 
fishtop_records's Avatar
 
🎧 15 years
Maybe I'm missing something, but people use
snakes to run 2, eight, or sixteen mic feeds
all the time. Many are 50 or 100 feet long.
That is why we use balanced cable.

What is different here?
Old 17th May 2003
  #4
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Roland's Avatar
 
2 Reviews written
🎧 15 years
Please!!

With standard studio mic cable you have to be running around 300 ft or more before you start getting any hf roll that can affect performance. Here you are talking about a kick drum!!

I would suggest that almost any of your favorite album recordings were done with lengths well in excess of the run you are talking. People involved in critical classical work are using mic lead runs usually of between 50-100ft. So take the cork out your ass and get on with the job! tutt

Regards


Roland
Old 17th May 2003
  #5
Gear Nut
 
🎧 15 years
Yup, and installation wiring in a studio can run to 50' easily.
Old 19th May 2003
  #6
Moderator
 
Tim Farrant's Avatar
 
🎧 15 years
Yes, the long cable runs in some studios are a reality - but because it's all installed, you just use it and never get to hear the diffrerence between a long/short run. Has anybody ever tried taking the preamp out into the studio and plugging the mic directly in and sending line level back to the controlroom ? Try it sometime - you may be amazed at the difference !!

Tim
www.buzzaudio.com
Old 19th May 2003
  #7
Gear Nut
 
🎧 15 years
Hello Tim.


Quote:
Avoid using star quad cable as this generally has a higher capacitance between legs.
Im curious about this. I use Canare star quad in 35 foot lengths all the time in my studio.

Does the higher capacitance roll off the top end ?

I have heard of bringing the preamp close to the mic and using line level from there. I may have to try it.

P.S. Off Topic. Hello Mike. Thanks again for the tip. Steve is great. We'll have to get together soon.
Old 21st May 2003
  #8
Moderator
 
Tim Farrant's Avatar
 
🎧 15 years
Hi Lamp,

The cable has to be pretty long to have an effect on most mics.

Looking at the spec for Canare L-4E5AT star quad, the capacitance between conductors is given as 164pF/m. The capacitance between conductors and sheild is given as 222pF/m.

However, spec for similair sized 2 conductor L-2E5AT cable is 79pF/m and 140pF/m respectively.

Quite a big difference. Lets say we have a mic with a 200ohm output impedance, that's 100ohm per leg. Without showing all the calc's here, I figure a 50m length of star quad would introduce a high freq rolloff at 115kHz. The 2 conductor rolloff is about 177kHz. You might say that this roll off is of no harm, but it does limit transient performance IMO.

Note that this does take into account any output inductance which will also react with cable capacitance, which may result in "ringing" and/or further high freq attenuation.

Cheers
Tim
www.buzzaudio.com
Old 21st May 2003
  #9
Gear Maniac
 
fishtop_records's Avatar
 
🎧 15 years
"transient performance" are critical to
sounding real.

Tim, while you say the calculations "roll off"
you don't say by how much. Is this
a standard 3dB per octave filter? or something
more serious. Being down 3 dB at 230kHz
it probably no big deal (TM).
Old 21st May 2003
  #10
Moderator
 
Tim Farrant's Avatar
 
🎧 15 years
Yes, the roll off would be gentle, 6dB per octave, but this only accounts for the resistive components, as I said, the inductive component complicates matters and the overall effects are why you CAN actually hear differences in cable types and lengths.

Tim.
Old 21st May 2003
  #11
Lives for gear
 
Roland's Avatar
 
2 Reviews written
🎧 15 years
Quote:
Originally posted by The Buzz
Hi Lamp,

The cable has to be pretty long to have an effect on most mics.

Looking at the spec for Canare L-4E5AT star quad, the capacitance between conductors is given as 164pF/m. The capacitance between conductors and sheild is given as 222pF/m.

However, spec for similair sized 2 conductor L-2E5AT cable is 79pF/m and 140pF/m respectively.

Quite a big difference. Lets say we have a mic with a 200ohm output impedance, that's 100ohm per leg. Without showing all the calc's here, I figure a 50m length of star quad would introduce a high freq rolloff at 115kHz. The 2 conductor rolloff is about 177kHz. You might say that this roll off is of no harm, but it does limit transient performance IMO.

Note that this does take into account any output inductance which will also react with cable capacitance, which may result in "ringing" and/or further high freq attenuation.

Cheers
Tim
www.buzzaudio.com

Well most studio condensors are around the 150 ohm mark, so that changes the calculation a little more.

The real mockery of all this arguement is that then we all want to couple this mic to some "esoteric" valve mic pre. What about the ringing in the transformer, microphonic valves, distortion?

Starquad is great for broadcast situations, but most of us here will be using standard twin. In all my years recording I have never had to question possible HF loss in mic cables or lack of transient performance, though I have many times heard differences due to temperature and humidity changes on a session.

Regards


Roland
Old 22nd May 2003
  #12
Gear Nut
 
🎧 15 years
Quote:
I figure a 50m length of star quad would introduce a high freq rolloff at 115kHz. The 2 conductor rolloff is about 177kHz. You might say that this roll off is of no harm, but it does limit transient performance IMO.
Tim, when I think of transient performance.... I think of something like how fast and accurately a speaker can reproduce a signal as in "detail". Are we on the same page here?

If so are you saying there are signals present in a mic cable at 177 kHz that my dog can't even here, " Im asumming we are talking harmonics here" and these signals,or lack of these signals, effect the transient detail?
Old 22nd May 2003
  #13
member no 666
 
Fletcher's Avatar
 
🎧 15 years
Quote:
Originally posted by The Buzz
Avoid using star quad cable as this generally has a higher capacitance between legs.
Except in high RF environments when 'star quad' cable will be your only salvation...
Old 22nd May 2003
  #14
Gear Nut
 
🎧 15 years
Flecther wrote
Quote:
Except in high RF environments when 'star quad' cable will be your only salvation...
Right. Istarted using star quad years ago when noise was running rampant through my cheap tascam stuff. Things are much better now with new gear and location.

So someone give me the short and skinny in layman terms. "im a drummer at heart"tutt Don't go there!

Do I need to get a mogami cable and do some a/b's ? Am I losing high end?fuuck me!
Old 22nd May 2003
  #15
Lives for gear
 
Saucyjack's Avatar
 
🎧 15 years
I'm on star quad full time as well....
I may need a 12 step program

I have a few 2 strand cables and I don't think I could blindly pick between star quad and twin....but my ears suck.
If it ain't broke don't fix it.
Old 23rd May 2003
  #16
Moderator
 
Tim Farrant's Avatar
 
🎧 15 years
Quote:
Originally posted by Fletcher
Except in high RF environments when 'star quad' cable will be your only salvation...
True, but good noise immunity is up to the ability of the mic pre to reject RF signals. If the common mode rejection ratio of the preamp is poor, then the type of cable used will make little difference.
Quote:
Originally posted by lamp
Tim, when I think of transient performance.... I think of something like how fast and accurately a speaker can reproduce a signal as in "detail". Are we on the same page here?

If so are you saying there are signals present in a mic cable at 177 kHz that my dog can't even here, " Im asumming we are talking harmonics here" and these signals,or lack of these signals, effect the transient detail?
Well yes, wether this effect is audible or not would be a matter for listening tests, but you can certainly see the difference to a 10kHz square wave that is band limited at 115kHz. I have a friend (Steve) who recently purchased some Slinkylinks mic cables. This cable uses a fine silver wire inside a plastic tube with air as the dielectric. It has very low capacitance. Steve was skeptical but when he tried it was blown away with the difference it made to the sound of his mics. There has to be a reason for it !!

Heres a link to Slinkylinks for those interested.

Cheers
Tim
Buzz Audio
Old 23rd May 2003
  #17
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Roland's Avatar
 
2 Reviews written
🎧 15 years
Quote:
Originally posted by The Buzz
True, but good noise immunity is up to the ability of the mic pre to reject RF signals. If the common mode rejection ratio of the preamp is poor, then the type of cable used will make little difference.

Well yes, wether this effect is audible or not would be a matter for listening tests, but you can certainly see the difference to a 10kHz square wave that is band limited at 115kHz. I have a friend (Steve) who recently purchased some Slinkylinks mic cables. This cable uses a fine silver wire inside a plastic tube with air as the dielectric. It has very low capacitance. Steve was skeptical but when he tried it was blown away with the difference it made to the sound of his mics. There has to be a reason for it !!

Heres a link to Slinkylinks for those interested.

Cheers
Tim
Buzz Audio

I'm sorry but I can't agree with you on either of these points.

If you have cable that doesn't have good RF rejection even with high quality pre's you will get interference.

As I said in an earlier post most people here are using standard twin mic cable not starquad, this coupled with the average impedance of a pro mic being 150 ohms not the 200 you used for your earlier calculation even on a 50m length is going to give them much better than the 115 khz bandwidth you are talking about. Now take into account the bandwidth limitation of the microphone (we will give some latitude here and say they are using a really high quality SD condensor like a DPA) this is limited to 20khz. However low the capacitance is on the silver cable your mate is trying we are going to be talking about miniscule differences between that and a good quality studio mic cable. What length of this is he using? I take a bet not more than about 10-20 metres. This is going to mean roll-offs around about 500khz on very ordinary mic cable! Has he conducted controlled blind listening tests, and can he reliably pick out the esoteric stuff every time? If he thinks he can here a difference he is deluded. There is a guy in the States that has put up a substantial amount of money for anyone that can do this in a properly conducted blind test. If they fail he keeps their cables, apparently no takers, I wonder why?

I'm all in favour of using good quality signal leads and connectors, but this esoteric cables stuff is a pure rip-off. There are plenty of ways people can spend their money in this industry costructively to get a better sound, cables like this are just not one of them!

Regards


Roland
Old 23rd May 2003
  #18
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littledog's Avatar
 
🎧 15 years
GREAT post, Roland!
Old 23rd May 2003
  #19
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bjornson's Avatar
 
🎧 15 years
I've got to agree with "the buzz". Since i started placing critical preamps in the tracking room and limiting mic cable length to 5', The sound really opened up. On all our remote recordings we do the same thing and the pa's REALLY sound better with line level coming down the pipe!
Old 24th May 2003
  #20
Moderator
 
Tim Farrant's Avatar
 
🎧 15 years
Quote:
Originally posted by Roland
I'm sorry but I can't agree with you on either of these points.

If you have cable that doesn't have good RF rejection even with high quality pre's you will get interference.
Please enlighten me on how cable rejects RF ? If you mean the sheilding, then at RF there is really no such thing - it gets in everywhere. The sheild may attenuate the interference, but it's still there and indeed will be present on the sheild itself. ALL WIRE IS AN AERIAL of some sort !!
Quote:
As I said in an earlier post most people here are using standard twin mic cable not starquad, this coupled with the average impedance of a pro mic being 150 ohms not the 200 you used for your earlier calculation even on a 50m length is going to give them much better than the 115 khz bandwidth you are talking about. Now take into account the bandwidth limitation of the microphone (we will give some latitude here and say they are using a really high quality SD condensor like a DPA) this is limited to 20khz.
Remember however that in my original calculation we did not take into account the reactive elements, which further complicates the issue. Also, you will probably find the output impedance of the mic rises with frequency, especially so with transformer output mics, and could be as high as 1000 ohms at 20kHz. The response of the mic might be specified out to 20kHz, but it's not a brickwall at that frequency, the mic is still capable of picking up energy, albeit attenuated, for least another octave.
Quote:
However low the capacitance is on the silver cable your mate is trying we are going to be talking about miniscule differences between that and a good quality studio mic cable. What length of this is he using? I take a bet not more than about 10-20 metres. This is going to mean roll-offs around about 500khz on very ordinary mic cable! Has he conducted controlled blind listening tests, and can he reliably pick out the esoteric stuff every time? If he thinks he can here a difference he is deluded.
Steve demo-ed the cable before buying it, I did not hear it, but he's not the sort of guy to be sucked in by hype. I imagine he heard enough improvement to consider the investment.
Quote:
I'm all in favour of using good quality signal leads and connectors, but this esoteric cables stuff is a pure rip-off. There are plenty of ways people can spend their money in this industry costructively to get a better sound, cables like this are just not one of them!
OK, we will agree to disagree Sure, there is a lot of hyped up **** out there but as bjornson discovered, it can make a difference.

Tim
Buzz Audio
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