Long Cable Runs

[WVUtubadude]

So I vaguely remember someone saying that for long cable runs, it is a good idea to put a pre close to the mic and run the line level signal the rest of the distance. This got me thinking about an upcoming job...

After getting the specs of an auditorium I will be working in in a few months, I found that it is going to take at least 200' of cabling to get from where the mics will be flown to where I will be. Would it be worth it to get some good pres and stick them up in the catwalks above the mics and run line level signal over however long the run will be?

[joelpatterson]

It might be a good idea, but it might also be a good idea "on paper" that had whirlygigs of unintended consequences... like when you ask for power up on the catwalks?

But then, I am always one for leaning however much is necessary on the crew of a hall-- and you will never discover some new and brilliant method by sticking to the tried and true!

[MichaelPatrick]

Good cable with clean XLR connectors is important no matter what you do, especially if they run near lighting power which is pervasive in a catwalk.

Joel is right. If you need to put preamps up there check out the power to make sure it's clean. SCR dimmers play mean with low level audio.

If you have good mic cables and your mics are condensers it should be fine. But if you are using ribbon mics putting some kind of head amp nearby is safer.

[NorseHorse]

So I haven't used the Fetheads, but if I were routinely doing cable runs of over a couple hundred feet, I'd check them out. They have a version now that passes phantom power. It's an in-line 18db preamp wherever you need it and it bypasses the risks associated with power in odd spaces.

Triton Audio FETHEAD Phantom | Microphones @ ZenProAudio.com

[Corran]

I routinely run 200' or more lengths of cable when I hang mics for the local symphony. I never have a problem (using starquad cable). Running condensers usually. I have done ribbons once or twice with the mentioned Fetheads, worked fine as well.

In my situation, there is power available in the catwalk but the switch that turns it on or off is in the back of the hall and I never know if it'll be on or off or even switched off in the middle of a recording. I wouldn't want to rely on unknowns like that - be sure to check that kinda thing out if you go that route.

[TranscendingM]

The key elements are:

- Having low output impedance
- Having a high impedance balanced differential input

[TRANQUILO]

Use balun's that use cat5 cable. Cat 5 cable is cheaper and noiseless. A balun permits loooong runs of line audio via cat5. You will need a balun on each end. If not then a balanced cable will do fine. Maybe wireless?

[ghellquist]

The mic manufacturers gives advice on maximum cable lenght. Most says that for a standard condensor mic you should not go above 300 meters ( about 1000 feet ). 200 feet is well inside that maximum so I would not worry.

// Gunnar

[djgizmo]

Originally Posted by TRANQUILO

Use balun's that use cat5 cable. Cat 5 cable is cheaper and noiseless. A balun permits loooong runs of line audio via cat5. You will need a balun on each end. If not then a balanced cable will do fine. Maybe wireless?

I could have swore I asked about something like this and someone said this was bad due to the noise one would pick up on the line.

[Plush]

200 feet is easily within the range of proper usage.

Going line level is always a good idea but is not required.

Golf broadcasts routinely run a mic down a 1500 foot mic cable.
What's pretty funny about a golf broadcast is that the whispering of the announcers is often taking place thousands of feet away from the hole where play is under way.

[tourtelot]

Originally Posted by TRANQUILO

Use balun's that use cat5 cable. Cat 5 cable is cheaper and noiseless. A balun permits loooong runs of line audio via cat5. You will need a balun on each end. If not then a balanced cable will do fine. Maybe wireless?

I have considered that. It would be great to do a real A-B on Cat5 vs. Starquad. If the results were acceptable (whatever that might mean for each engineer), it could solve a lot of long-run problems. Oh yeah, TWO mics on each piece of Cat5!

D.

Still have to power the mics in the grid, but that could be as easy as a Denecke PS1.

[WVUtubadude]

So it probably won't be an issue...but then again, it could be an issue? At what distance would running line level be a must with condensers?

[Don S]

I have friends with degrees in electrical engineering that say that there should be no audible difference, but I can tell you that I do hear a difference with my rig when it is running 200 feet of mic line as opposed to a single 25ft cable. As mentioned, it should not (and probably won't) give you any problem, but is the best solution. I know many engineers here that prefer to run aes or madi as opposed to mic line. FWIW. Cheers!

[panatrope]

Top end response depends on the mic. Schoeps, Sennheiser MKH's etc have a low output impedance and resistive (35 ohms in the case of Schoeps). For typical values of resistance and capacitance per 100m for mic cable, the impact cuts in around 100kHz. (I have used Schoeps on the end of a 100m+ run without noticeable degradation.) Use mics with higher impedance (150 - 200 ohm), or transformer out with a high inductive component and you are more likely to have noticeable impact at the top end. Avoid any grounding issues, and use well shielded or star quad cable to avoid interference from lighting and high impedance well balance inputs, and minimum number of connectors on the way.

Of course you could use digital mics ...

[MichaelPatrick]

Originally Posted by WVUtubadude

So it probably won't be an issue...but then again, it could be an issue? At what distance would running line level be a must with condensers?

Hard to say because there are just too many factors in play; even the maintenance/condition of every piece of gear can change from one day to the next.

Assuming your gear is in good condition and the catwalk and lighting are not a maintenance nightmare, you should be fine. Just run your cables away from power lines and cross them at 90 degrees wherever crossing is unavoidable.

[MichaelPatrick]

Originally Posted by Plush

200 feet is easily within the range of proper usage.

Going line level is always a good idea but is not required.

Golf broadcasts routinely run a mic down a 1500 foot mic cable.
What's pretty funny about a golf broadcast is that the whispering of the announcers is often taking place thousands of feet away from the hole where play is under way.

That's true for what it is, but I don't think it's much help to suggest that noise and fidelity standards for sports and music are comparable. Spoken voices are limited both spectrally and dynamically, and broadcasters often process them with EQ and dynamics to make them consistent and intelligible on small radios and TVs.

[TRANQUILO]

The twisted pairs of the cat5 cable defends against RF interference via twisting, the key is to NOT un-twist the pair you are using with the baluns. Baluns are available in stereo. The twisting of the wire acts like a coil so you dont get interference. Also the baluns are not sending audio signals but using a constant electrcial signal with audio imposed on to it much like a FM radio except with wires. I know sweetwater sells what is called a digital snake that has a stage box with 24 inputs and 8 returns and a box for the mixer with the same 24 outputs and 8 sends as the stage box and uses two little cat5 cables to link them together.

[philper]

Originally Posted by TRANQUILO

The twisted pairs of the cat5 cable defends against RF interference via twisting, the key is to NOT un-twist the pair you are using with the baluns. Baluns are available in stereo. The twisting of the wire acts like a coil so you dont get interference. Also the baluns are not sending audio signals but using a constant electrcial signal with audio imposed on to it much like a FM radio except with wires. I know sweetwater sells what is called a digital snake that has a stage box with 24 inputs and 8 returns and a box for the mixer with the same 24 outputs and 8 sends as the stage box and uses two little cat5 cables to link them together.

I seem to recall some issue w/ low quality transformers in low-cost Cat5 baluns degrading audio, but perhaps I'm confusing that with some other form of transmission. I use Cat5 (w/ cheap baluns) for audio send and video return from video assist systems (non-critical) when I'm on my cart--and that has worked GREAT. The systems like Sweetwater sells (Aviom AN16 etc) have not only the mic pre but the ADC in them, and are sending what I think is a proprietary digital signal for all those channels down those lines, which requires their own demuxing at the other end (like in a digital console). This last seems like it would be a great thing for touring. I have seen pictures of Mark Ulano's rig (Big Hollywood stuff) and that's how he runs his audio distro now.

Philip Perkins

[WVUtubadude]

A report from the building's facilities manager says that there are outlets on the catwalks that are on the same circuit as the wall outlets at ground level, so power isn't going to be an issue if I do end up running line level.

I'm picking up that the 250' runs probably won't be an issue, but just to be safe, I am going to get a decent four channel pre to keep handy.

[DannyL]

I have done a fair bit of orchestral recording for television.

My main (ORTF) pair is generally at least 250 feet from a mic pre. Sometimes almost 1000. I use a pair of Schoeps into ATI 8MX2 pres and have yet to encounter a problem. I use the same length of cable for both mics of the pair. Also, and this cannot be stressed enough: TEST THE SIGNAL PATH BEFORE INSTALLING!!!! I plug the cables into the mics, and into the mult, (if one is used) and into the mic pre before I roll out the cables. The small amount of time this takes is well spent, especially if you need to troubleshoot after installation.

During an sports award show at Radio City, we discovered that almost all the mults needed maintenance. Fortunately we were able to do the repairs before the house staff sequestered the cables. The best part was that our cables were run last and we were therefore able to wrap first.

Regards;
Danny

[sonare]

If you are not the DIY type then consider Insta-snake:
http://www.gearslutz.com/board/f21/f...on-492654.html

The least expensive source of shielded CAT5 with Ethercons on each end that I could find was Redco.

Rich

[RobAnderson]

Not sure how many channels you are talking here, but for a practical consideration, hauling rack cases with mic pre's up and down the ladders in a catwalk can prove difficult and hazardous, and I doubt if there would be any noticeable difference in the audio quality if you are using good stuff.

Another consideration is that if you have to adjust the gain, you will be a long way from your gear, so if you are putting the mic pre's in the catwalk, you may wish to put your entire rig there as well. Using my small rig, I have recorded entire concerts while being positioned in catwalks. However, it is usually hot and uncomfortable at best, and I am carrying everything I need in a single suitcase. I should mention that the few times I have done this, it has been more a matter of practical necessity rather than by choice.

However, another practical consideration is if you are hanging mic's and working without the help of a crew, having some way to hear and adjust the hanging mic's without having to leave the catwalk is a wonderful thing - a small Mackie can save you a few trips while you finalize the adjustments.

[sonare]

Originally Posted by djgizmo

I could have swore I asked about something like this and someone said this was bad due to the noise one would pick up on the line.

I recall someone mis-reading the Instasnake data sheet and seeing a hign noise figure-- at 100kHz.

No problems here. But this does not mean to ignore good operating practice in crossing serious AC and SCR dimmer stuff.

Rich

[chris319]

Does this auditorium not have any clean existing audio lines you can use? I would be quite surprised if it didn't.

Why guess? 200 feet = 61 meters. With a 150-ohm mic and cable capacitance of 185 pF/m (Canare L-4E6S), you're down 3 dB at 94 kHz.

There are some gearslutz who will say they can hear 94 kHz. Some guy whose eardrums have been blown out by years and years of high-dB rock music telling me he can hear 94 kHz? Yeah, right. He probably can't hear anything above 5 kHz.

Calculation of cable length, cable capacitance C, and cutoff frequency microphone mic cable capacity wires XLR - sengpielaudio Sengpiel Berlin

Canare Corp.: Star Quad Series: Star Quad Microphone cable(L-4E6S / L-4E5C)

[WVUtubadude]

Originally Posted by chris319

Does this auditorium not have any clean existing audio lines you can use? I would be quite surprised if it didn't.

That was my first thought when I saw what I would have to work with. Catwalk access couldn't be further away from the stage box, which would be a huge pain in the ass to run cable to. I am actively trying to get the powers that be to reconsider letting me use a tall stand in the center isle or to reconsider their feelings about running cable through the ceiling panels directly above where I plan to set up to avoid the hatches they want me to use (and the extra 100' that comes with it).

All this physics stuff makes it seem like 200-250' shouldn't be a problem if the facility is dead set in their ways.

The instasnakes look interesting, I might check them out some time in the future.

[Mark A. Jay]

Originally Posted by WVUtubadude

So I vaguely remember someone saying that for long cable runs, it is a good idea to put a pre close to the mic and run the line level signal the rest of the distance. This got me thinking about an upcoming job...

After getting the specs of an auditorium I will be working in in a few months, I found that it is going to take at least 200' of cabling to get from where the mics will be flown to where I will be. Would it be worth it to get some good pres and stick them up in the catwalks above the mics and run line level signal over however long the run will be?

I am a big believer in simplicity, and adding a pre (IMHO) is just another component in the path that could fail (for any number of reasons); the signals as-are should be perfectly fine. Plus, all microphones feature a relatively low output impedance (a good thing), and thus the resistance of the wires themselves will result in minimal attenuation - even at 200 feet.

Like others who have posted similar experiences, I have routinely run 200' cables without incident and without any signal loss issues. That's the beauty of a balanced, low impedance line driving a differential input. Plus, if you are running condensors, you always have the option of phantom-powering them from your gear, and thus, if there is signal absence (apart from a cut cable), the fault can only be the recorder's phantom supply that is responsible for the absence of signal...and with dynamics (though I don't know if you'd be using those) you need not even worry about phantom.

[studer58]

Occasionally the best 'long cable run' is no cable at all ! Let me share a recent experience with you regarding the Zoom R16, which (like the H4) has a pair of in-built mics, as well as facilities for phantom powering a pair of external condensors. On a recent choir recording the Zoom (running on internal AA batteries) came in very handy indeed. The choir made a trademark for itself of moving around a very big cathedral while singing...great for creating a 'living surround audio experience' for the audience, but damn hard to mic up and get good coverage. I had most of the mic locations covered with very long cables connected to my DAW, but one placement was completely beyond the reach of any of my cables, waaaay up in the loft 100's of metres away from my DAW. Yet I wanted a sense of close focus on this singer, as well as the hugely washed out reverby sound that the audience would hear as part of the intended sound. Solution: I placed my R16 on 6 AA cell battery power (around 3 hours' worth, plenty long enough) up there with him about a metre from his singing position, recording to the built-in mics, and later on in the DAW I 'floated in' his closer mic positioning thanks to the Zoom. Just a bit of the close Zoom presence plus the the huge room sound (I was also careful to delay his close mic by around 300msecs !) added up to a great result that would've been impossible without the Zoom. So it pays to think of the R16 as a standalone battery powered spot mic on occasions where cables won't get you there...just thought I'd share this with you. I also could just as easily have connected a condensor mic or two and a run them off the Zoom's phantom powered inputs....but not needed on this occasion.

[Rick Sutton]

Originally Posted by studer58

Occasionally the best 'long cable run' is no cable at all ! Let me share a recent experience with you regarding the Zoom R16, which (like the H4) has a pair of in-built mics, as well as facilities for phantom powering a pair of external condensors. On a recent choir recording the Zoom (running on internal AA batteries) came in very handy indeed. The choir made a trademark for itself of moving around a very big cathedral while singing...great for creating a 'living surround audio experience' for the audience, but damn hard to mic up and get good coverage. I had most of the mic locations covered with very long cables connected to my DAW, but one placement was completely beyond the reach of any of my cables, waaaay up in the loft 100's of metres away from my DAW. Yet I wanted a sense of close focus on this singer, as well as the hugely washed out reverby sound that the audience would hear as part of the intended sound. Solution: I placed my R16 on 6 AA cell battery power (around 3 hours' worth, plenty long enough) up there with him about a metre from his singing position, recording to the built-in mics, and later on in the DAW I 'floated in' his closer mic positioning thanks to the Zoom. Just a bit of the close Zoom presence plus the the huge room sound (I was also careful to delay his close mic by around 300msecs !) added up to a great result that would've been impossible without the Zoom. So it pays to think of the R16 as a standalone battery powered spot mic on occasions where cables won't get you there...just thought I'd share this with you. I also could just as easily have connected a condensor mic or two and a run them off the Zoom's phantom powered inputs....but not needed on this occasion.

Thank you for sharing that! Very clever use of the Zoom.

[Mark A. Jay]

Originally Posted by chris319

Does this auditorium not have any clean existing audio lines you can use? I would be quite surprised if it didn't.

Why guess? 200 feet = 61 meters. With a 150-ohm mic and cable capacitance of 185 pF/m (Canare L-4E6S), you're down 3 dB at 94 kHz.

There are some gearslutz who will say they can hear 94 kHz. Some guy whose eardrums have been blown out by years and years of high-dB rock music telling me he can hear 94 kHz? Yeah, right. He probably can't hear anything above 5 kHz.

Calculation of cable length, cable capacitance C, and cutoff frequency microphone mic cable capacity wires XLR - sengpielaudio Sengpiel Berlin

Canare Corp.: Star Quad Series: Star Quad Microphone cable(L-4E6S / L-4E5C)

Nice job.

In a system where a balanced output (such as found in pretty much all 'serious' microphones) feeds a differential input, for any 'sane' cable run the losses are wholly negligible as you have pointed out; although I spoke to the magnitude losses in my post, I only alluded to the effect of capacitance and inductance on frequency response (as I was, as I wrote my previous post, just thinking to myself that 'it just doesn't matter'). Moreover, it's nice to see links that allow people to see what the MATH reveals...and math is never wrong. True, it may reveal an answer that you don't like, but it's never wrong.

Granted, in high-Z unbalanced systems, capacitance can be a very real issue (such as in guitar cables etc), but lest we forget, these issues (and things like induced noise) are precisely why the concept of balanced lines feeding a differential input were invented (or 'discovered' if you prefer).

I know some people will say they can hear a difference between balanced cables in such systems, but I maintain that if they listened to purported differences in such cables using established controlled listening tests and paired comparison techniques (in conjunction with adequate statistical controls as to their vote coinsistency such as circular triads), they could not consistently tell a difference between cables, and as such, that's nothing more than 'chance' (and 'chance' is just anotehr word for 'guess')... but that's a whole 'nother topic that's been thrashed many times, and people believe what they want to believe. Again, my comments here are confined to balanced/differential systems and not necessarily to cables found in high-Z unbalanced systems.

Also, thanks for restating the obvious...or what should be the obvious truth (and that's not a slam, it's praise) about being able to hear such insanely high frequencies.

Kudos.thumbsup

[daven]

It seems like perhaps an inline mic pre is perhaps interesting - but probably at distances considerably above the 60m you are dealing with - that sort of length should not really present a problem.

Canford makes one:
FEL MINI-MICBOOSTER MICROPHONE PRE-AMPLIFIER Extended

and Rode does another, but can't find it right now.