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Concert Hall & Long Distance Digital?
Old 26th November 2009
  #1
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teletype1's Avatar
 

Question Concert Hall & Long Distance Digital?

hi everyone,

i've been mulling over this problem for a few months since i started at CSU... here's the deal:

my recording engineers tape EVERYTHING that goes on in our concert hall -- mostly classical concerts. Whoever built the performing arts center here spec'd things out right, there are tons of mic lines and tie lines that run back to our central recording room from the three halls. however, the length of the lines is huge... the closest venue is probably 100 feet, which means the mic lines are probably longer with all the twists and turns in the conduits.

so, we have a relatively decent infrastructure, but the amount of noise we accumulate over the mic run is unacceptable to me.

we've been using preamps racked in a case on stage for serious recordings so we can pass the signals to the studio balanced, at line level. however, i want to install a new isolated system in the main concert hall, and potentially do the digital conversion in the hall.

does anyone have recommendations for a multichannel (at least 4) long distance digital solution? i don't mind pulling new wire or fiber from the hall to the studio, but i want to reduce the number of interconnects.

ideally: Decca Tree in the concert hall -> Canare StarQuad -> Mic Pres -> Digital Conversion -> Long cable run -> ProTools.

any thoughts ?

-m
Old 26th November 2009
  #2
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NetworkAudio's Avatar
I just finished the sceletal requirements for a new concerthall with a separate scoring stage.
We will go with either
Millennia, Crookwood or Grace remote controlled preamps controlled by a separate harware remote or computer as well as the PTHD

Onstage and catwalk-mounted madi system such as euphonix or the like

Vandamme lowloss cable for clocking and video including two strands of cable to each posision that have precicely the same length into the controlroom for optimum clocking

Optical madi for the audio going into a Deltalink/PTHD

AES lines to all relevant posisions to have possibilities for analogue as well as AES
CAT6 multicables to all posisions
Old 27th November 2009
  #3
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The University I went to had a sweet LightViper fiber optic rig with remote millennia. I would check out something like that.
Old 27th November 2009
  #4
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teletype1's Avatar
 

thanks for the recommendations so far guys --

unfortunately we are stuck with a Digi 002 for the PT interface for the moment (long story), so i'm stuck clocking to a Rosetta via SPDIF -- and, as a side note, everything online about the Digi's internal clock is totally true -- the sound clears up and is much crisper when pulling off of the Rosetta.

i've heard there is clocking problems with ADAT lightpipe -- has anyone experienced this? if so, is there a problem with long coax cable runs to drive the clock? if we do put the convertor in the hall up on the catwalk or something, we can run a coax back through the pipes or use the existing video tie lines. but will there be quality loss or jittering with a big long clock run back from the studio ?

grace is definetly on my radar as the main preamp -- we had one at U. Richmond and it sounds incredible.

anyone have a spec on AES cable length limits?

best,

m
Old 27th November 2009
  #5
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John Willett's Avatar
 

Smile

RME Micstacy and run back to PT via MADI.

Or digital mics, RME 842 and again run back to PT via MADI.

Or a mixture of the two as the Micstacy and 842 can be used together and run back under a single MADI cable.

I think the AES cable run can be 200-metres with a digital mic. at 24/96.

Old 27th November 2009
  #6
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Yannick's Avatar
 

sommer cable
or
Gotham Kabel AG | 16508 GAC-8pair mini AES Multipair cable for digital transmission

200-300m should be without problems.
Not with standard mic cable, I usually run into problems in bigger halls with installed cable (between 50m and 70m problems start ...)
Old 27th November 2009
  #7
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If there isn't some fault in the analogue cabling, mic signals should easily travel 900 ft without noise or treble loss. That is, if the mics' Z is in the 50 Ohms range.

Apparently in this case there is some problem, either with power lines running too close to the mic lines, or bad connectors, or mics with way higher impedance. Re-doing the cabling might be the cheapest way?
Old 27th November 2009
  #8
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Yannick's Avatar
 

please read the thread title ...
Old 27th November 2009
  #9
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NetworkAudio's Avatar
Quote:
Originally Posted by teletype1 View Post
anyone have a spec on AES cable length limits?
To my best knowledge the limit is as follows:
Cable losses should not exceed 6 dB at 1 MHz without cable EQ at 1FS
For 2FS keep the attenuation less than 6 dB at 2 MHz
Old 27th November 2009
  #10
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sonare's Avatar
You imply that you run from side-stage to control room at line level but the noise is unacceptable. You should be good for 1000ft. I think that careful and methodical trouble-shooting may eliminate your problem. If it is not buzz/hum/hash then your problem is with the expensive bits that your administration may not be eager to solve with $$. If the contractor spec'd industrial micpres then that is most likely your problem.

You did not mention having coax already run for MADI. 100m of tactical LCLC optical will be about $1k, and I would not try to pull the cheaper orange "zipcord" through a plenum. Then the big problem will be controlling the gain and what digital format to make your long run. With 24-bit, levels should not be a worry, and if you keep a record of mic/position/ensemble you should be able to set things ahead of the performance and see peaks of about -10 (+/-2dB).

I will forward this thread to a friend who has been down a similar path while improving things at a major conservatory.

Rich

Rich
Old 27th November 2009
  #11
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teletype1's Avatar
 

introduced noise, etc.

hi again all --

pkautzsch: i suspect there is accumulated noise on the line, it sounds like more than just preamp noise. the current geometry is:

- 3 EarthWorks QTC series in decca tree
- left and right go direct up the sound reinforcement booth, into an EarthWorks 1024 preamp (used to be a LAB 102, but i changed it because the outputs aren't balanced, if you can believe it).
- center channel gangs up with Ls and Rs mics in the back and run the opposite direction -- down through the organ loft into a mic jack, which then runs to the booth, and into the EW 1024
- EarthWorks 1024 3-channels of output patch into tie lines -- which have exposed connectors on both ends (male and female XLR so they are bidirectional)
- Tie lines end up in the studio, where we patch (again) into the Apogee AD16x, then feeds via lightpipe into PT.

So, currently there are at least 5 places on the line where it's not balanced anymore... you can see why i want to replace it... plus, and it's just me, the EW mics and pres are not my taste. gonna spec in some Geffel M296's instead.

i guess the burning question is -- is it worth installing a long digital run, keeping the mics, pres, and AD's as close together as possible, or should we continue to convert AFTER the long, noisy cable run?

iZotope RX is our best friend right now.

-m
Old 27th November 2009
  #12
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NetworkAudio's Avatar
One way to go could be a trio of mkh800. They are very very quiet and send a seriously hot signal down the line.

Get some for demo and see if the noise gets any better.
Old 27th November 2009
  #13
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Hi teletype1!

Where does the balanced > unbalanced thing happen? Are you saying that the 1024 output are not feeding the AD16 via a balanced cable?

Cables of 100-200 feet should not cause much of a problem.

I'm a little bit curious about the distance from the mic's to the stage and the typical gain setting on the 1024. I suspect you're hearing the self noise of the EW mic's.


/Peter
Old 28th November 2009
  #14
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If I was in your position, I would look to keep things simple. The simplest way to deal with the issues of questionable install is to go with easy, widespread technologies. The first place Id look for that is with the various Ethernet based systems. You can remote control preamps from a distance (look at control for Grace and Millennia or Yamaha), then I would convert to an ethersound system. Cobra is also a possibility, but if you're running to PT LE and recording, I think you'll have better luck with Ethersound than Cobra (you can go 44.1KHz, lower latency, etc...)

Several venues around LA have gone that direction and it has been very successful. It is a robust interface and is reliable. Jitter specs are also pretty low so it sounds good.

A common implementation is the Yamaha AD8HR pres/converters through the NAI-48ES. gives headamp control from a number of yamaha consoles or a laptop with the interface software. There are Ethersound cards for yamaha digital consoles as well. A DM1000 could give you 16 I/O Ethersound and 16I/O on ADAT with 2 cards. Plus- omni outs that would give you a host of analog output options.

Just a couple thoughts...

--Ben
Old 28th November 2009
  #15
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Keeping things simple IMHO means:

8ch AES spec multicore (which you can still use as an analogue line, the noise issue will be gone anyway, because you will have a clean, uninterrupted cable)

Then eg a Gracedesign m802R + remote, plus AES option. This will use 4ch of the multi + 1ch for the remote controller. This leaves three lines for talkback and a stereo feed (analogue)
Old 28th November 2009
  #16
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Audiop: i think you misunderstood me -- the outputs of an EarthWorks LAB 102 preamp are _unbalanced_ -- the 1024 is balanced. i was pretty shocked that the LAB 102's were unbalanced, apparently EarthWorks wanted to keep another analog stage out of the circuitry. *shrug*. i suppose we could run them into a direct box (hehe).

anyway, we had two 102's driving the decca tree when i arrived here, i replaced them with the 1024 because the cable run after the preamp was upwards of 200 feet with nothing on the negative wire -- that fixed some of accumulated noise but i still don't like it -- thus, this thread

great suggestions so far guys -- pulling a 9-channel multicore snake was my first thought too, but i wanted to explore the long-distance digital thing. we do have direct coax lines (spec'd for video) so we could do MADI, which would be awesome... how much latency would be there though?

i agree that some of the noise may be from the EW mics... i want to get rid of them as soon as possible, even though the other faculty members here drool over them... i just don't like 'em.
Old 28th November 2009
  #17
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NetworkAudio's Avatar
Latency would depend on the particular AD converter, a few milliseconds typically.
Old 28th November 2009
  #18
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I think the LAB preamps are indeed balanced.. impedance balanced.

This will basically give you the same noise and interference supression as an active balanced solution since the hot and cold wires are connected to the differential inputs of the AD.

Impedance balanced will mean the signal is driven via hot and screen if the differential input is referenced to GND and via hot cold if the input is floating.

BTW, you can send the EW's to me! ;-)


/Peter
Old 28th November 2009
  #19
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avebr's Avatar
 

Quote:
Originally Posted by klaukholm View Post
One way to go could be a trio of mkh800. They are very very quiet and send a seriously hot signal down the line.

Get some for demo and see if the noise gets any better.
+1 thumbsup Great sound, clean and hot. If you can, you should demo them!

But I believe there's some install problem! I've done 75-85m or so of multichannel (24+16) on a theater project with 'not-that-great-cable' (far away from Mogami) and it was just perfect - no noise, no humming, extremly low loss! The employee had a very low budget, so surely we had to take extra care with grounding, putting AC cables far, etc... I would check the install first. (No more installs for me, I'm done!)

Also I just remembered: ETSLAN (Energy Transformation Systems, Inc. :: Home) has INSTASNAKE PA200S - adapters so you can transmit analog or digital audio thru ethernet cable. It's not a very know product but it's great - I have a pair and use all the time on mobile recordings - great to hang mics on the roof (when they have no infrastrutcture to do that).


all the best,
ave.
Old 29th November 2009
  #20
Thumbs up

Quote:
Originally Posted by avebr View Post
Also I just remembered: ETSLAN (Energy Transformation Systems, Inc. :: Home) has INSTASNAKE PA200S - adapters so you can transmit analog or digital audio thru ethernet cable. It's not a very know product but it's great - I have a pair and use all the time on mobile recordings - great to hang mics on the roof (when they have no infrastrutcture to do that).
Niiiiiice.
Old 29th November 2009
  #21
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Larry Elliott's Avatar
ETSLAN INSTASNAKE is a great product. Sure beats carrying around heavy multi cores.

You do need to ensure that the screen in CAT6 cable is connected if you want to use phantom power.
Old 29th November 2009
  #22
Gear Maniac
 

Hi there

I agree there might be some gremlins which once ironed out you may find the unacceptable noise goes, but doing to the A to D conversion on the stage will always be good news and remote pre amps in this instance are handy. I personally get on well with the RME Micstasy and bearing in mind your shows are live, the minimal benefits that might be achieved by using more exotic / expensive Grace Designs or Millenia are probably outweighed by noise of an acoustic nature such as air con etc. I do like Yannick's suggestion of AES 8 way snake which is a very robust technology and if you are not doing high track count it could work and there are plenty of good 8 channel mic pres with AES card although not that many with remote and you have to consider what additional cabling is necessary for the remote to be implemented. I do incidentally think there is a distance limitation with AES but am not sure what it is. On the Grace, the remote is achieved I think through some sort of 9 pin cable. With the Micstasy you can run AES without remote or get the Madi card and do the audio and remote control over the one protocol which could be seen as a slight advantage. The other thing to consider is that when we say remote mic pres, I don't think any of these work from inside Pro Tools software - you'd be running a different application and you may need to check whether it is cross platform if you are Pro Tools Mac. Grace on the other hand is a hardware remote and I agree again it is a beautiful product although it jolly well should be at that price.

Finally, please don't lambast me for what are just my own humble opinions on the matter.

Matt
Old 29th November 2009
  #23
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In no way are Millennia and Grace "exotic".
The Grace can be hardware, software or protools remote controlled while the millennia can be software (PC) or protools remote controlled.

The Grace hardware remote runs over regular mic cable, while the software remote and protools remote are both midi and as such need some sort of midi extender. Midi extension can be over mic cable or over ethernet.

The Millennia is controlled over ethernet for its software and the protools remote is done over midi in the same manner as the Grace.
Old 29th November 2009
  #24
Gear Maniac
 

Excellent - so now we know - don't scald me for using the word exotic - they are double the price and additional cable is required for remote whichever way you look at it - something additional to the signal. I was promoting the RME because of the need only for Madi for signal and control. Nevertheless the information is useful. I just hate the way people put things on this site and have decided not to bother posting helpful information any more.

Matt
Old 30th November 2009
  #25
Elk
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I think Kjetil merely wanted to make the point that no one should be put off using such equipment thinking that it is overly complex or finicky.

I don't believe he meant to belittle your post in any way, at least as I read what he wrote.

Plus, you provided some good info as well.
Old 30th November 2009
  #26
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Hear Technologies - Extreme Extender


* Extend ADAT® Optical cables up to 500 ft
* Uses standard CAT5E cables
* Does not affect sound quality
* Small size, durable construction
* Status LED's


Relatively cheap and works.
Old 30th November 2009
  #27
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The problem I have with optical, cat5e, cat6, audiolan etc etc is the day something does not work you have a problem.

With an AES snake, you can connect anything, AES or analogue.
Old 30th November 2009
  #28
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BTW I don't know what's happening here above me, but I was quite clear in a previous post about:

a. several hundred meters is no problem with AES over AES specific cable.
b. the Grace sends its control signal over standard mic cable.

We even send AES, analogue and control through ONE multi, no problems. Get one where the different cables are screened independantly.

On the topic of MADI: we thought about a MADI snake but:
a. it is more expensive (if you don't need the high track count)
b. you should get a spare
c. you should get a spare for the spare.

Because when it breaks, you have a problem. When someone cuts your AES multi, you can still put another multi, even a standard one if the distance is not too big.

Call me conservative ...
Old 30th November 2009
  #29
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yannick, I completely agree with you on the backup.
Ideally there should be an AES/analogue run along with Madi for safety as well as extra coax runs
(even with optical madi you may need a few low loss coax for clock)
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