Film-Tech Forum ARCHIVE: Looping Non-Sync Audio Source

This is topic Looping Non-Sync Audio Source in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=003555

Posted by Brian Tristam Williams (Member # 1235) on 06-09-2002, 10:15 AM:

This may be a little OT, but I know that there is a lot of ingenuity here.

We have 15 cinemas, and that means running 15 CD players for between-show background music. CD players can be difficult to keep maintained, and the music from one disc can get a bit stale if you stick around enough.

Question: If one had to loop all 15 cinemas to a multi-disc changer, or to a satellite music source, where can I find a simple decent amplification circuit that would allow me to split low-level audio signals 16 ways or more? I'm doing a test now looping 5 cinemas, but I notice that, the further from the source, the lower the signal level gets. I'd like a decent boost to send the signal via a star configuration to all 15 cinemas plus the lobby and bar areas.

------------------
"One man can make a difference."

Posted by Steve Guttag (Member # 268) on 06-09-2002, 10:37 AM:

Brian,

What you want is called a DISTRIBUTION AMP.

They are made by cinema audio maufacturers such as:

SMART (probably the least expensive and most popular though silly construction).

USL (nearly identical to the SMART but a more sensible card cage)

Both Component Engineering and Odyssey Products have a daisy chain method of distribution. The big advantage to these systems is that you don't have run separate lines from a central DA to each sound system. You start at one and go to the next and go to the next......etc until all cinemas are connected.

Lastly, there are Pro audio manufactuers that also make Distribution Amps too. Examples include RANE, BGW and Radio Design Labs plus many many others.

So, in short, there are many maufacturers out there for you to choose from to do exactly what you are trying to do.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Gordon McLeod (Member # 33) on 06-09-2002, 10:42 AM:

The Smart is the best bang for the buck and I like the concept of home running each screens NonSync
Also the Smart can have a compressor card added to control the level and a small amplifier card for lobby speakers

Posted by Paul G. Thompson (Member # 655) on 06-09-2002, 07:29 PM:

Be sure to have ALL the sound systems in the same primary power phase, unless you want a bunch of ground loop problems.

I would think a distribution amplifier with balanced isolated outputs would save a lot of grief. Otherwise, you might have to use some isolation transformers if you get overwelmed with ground loop hum problems.

Posted by Steve Guttag (Member # 268) on 06-09-2002, 07:37 PM:

Sorry to disagree with you there Paul....the phase should have virtually no affect on anything.

Ground loop hums are caused by just that...ground loops. Distribution Amps do take care of the grounding issues since the good ones are indeed transformer out (like the SMART).

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Paul G. Thompson (Member # 655) on 06-09-2002, 10:57 PM:

Steve, you are correct - as long as the grounds are ground and the neutral is neutral. However, in many buildings, old and new, it is seldom true. Both of us have seen some weird wiring in buildings.

You should see the mess I have to contend with at the radio station....Plug it in one receptical, the audio hums like a hummingbird. Plug it into another receptical that is on the same phase, and it is quiet as a mouse. It drives us nuts! Many times I had to use a distribution amplifier or an isolation transformer to eliminate the ground loops. Our electrical power in that building is so rottin' that we can't fix it without a complete re-wiring of the building.

But yes, a distribution amp is the way to go.

Posted by Gordon McLeod (Member # 33) on 06-10-2002, 10:08 AM:

Paul a distribution amplifier such as the Smart or Ultra is just that a transformer issolated source issolating each theatre
If proper shielding techniques are followed no one system should influence another

Posted by Paul G. Thompson (Member # 655) on 06-10-2002, 01:10 PM:

Hmmm....Gordon, I am going to take a close look at the USL and Smart Distribution Amplifiers. Those might be a "good call" for the radio station. The ones we use now are ok, but for future use, the USL and Smart might be better.

Posted by Manny Knowles (Member # 1171) on 06-11-2002, 06:06 PM:

I think it's important to use the right kind of wire for the hookup. I have to go and totally rewire a non-sync because tiny multiconductor computer wire was used and it was simply trailed exposed through the drop-ceiling.

I was advised to replace the wiring with Belden Special Purpose Audio cable.

If I understand correctly, this new wire will be two pairs of shielded twisted-pairs (4 conductor) and possibly also a "drain" wire. Does this sound right? I haven't actually received my new wire, so I haven't had a chance to examine it yet.

I'm also advised to run the wire through a metal conduit; not running freely through the ceiling and also not PVC.

This cinema complex has been experiencing SEVERE hum in the non-sync ever since the time of installation. They are using an older version of the Smart DA-226. I am using two of the newer ones and they have been trouble-free. If I'm still hearing the hum when I'm done with the rewiring then I'll start to suspect the distribution amp.

I'd appreciate any suggestions you might have. These people should have music. I know they'll be a lot happier with some tunes.

------------------
~Manny.

"The brown acid that is circulating around is not specifically too good."

-- An announcement in the film, "Woodstock: 3 Days of Peace & Music."

Posted by Gordon McLeod (Member # 33) on 06-11-2002, 08:47 PM:

I use Belden 9451 which is a two conductor plus foil shield or the west penn equivelent and run 2 to each booth
I usually just run it bove the tbar with out any problems

Posted by Manny Knowles (Member # 1171) on 06-12-2002, 06:07 AM:

Gordon:

Thanks for the Belden number. I went to their website and I see that they also make a 9451D (Dual) so you won't have to run two of the 9451.

What's your opinion about the computer multiconductor wire being the cause of the hum? These wires are tiny, tiny, tiny!

~Manny.

Posted by Oscar Neundorfer (Member # 458) on 06-12-2002, 06:37 AM:

Manny wrote:

"They are using an older version of the Smart DA-226. I am using two of the newer ones and they have been trouble-free. If I'm still hearing the hum when I'm done with the rewiring then I'll start to suspect the distribution amp."

Manny, for the older version to which you are referring, are you sure it is a DA-226? We made a model DA-8 which used resistively isolated outputs which is OK but nowhere nearly as good as the isolation provided by the DA-226 transformer isolated outputs.

Steve, the construction may be silly, but it is a fairly inexpensive method which has served us well over the years. The only real problem we had was with the card edge contact fingers not always lining up properly with the motherboard edge connectors. We solved this by routing locating notches in the plug-in cards which positively locate the fingers in the edge connectors.

------------------
Oscar Neundorfer
Chief Engineer
SMART Devices, Inc.

oscar@smartdev.com

Posted by Steve Guttag (Member # 268) on 06-12-2002, 08:21 AM:

Having the input/output connectors poke through the back of the card cage such that when you plug in the connector, you push out the card is just plain silly. This is certainly an area where SMART can improve their construction.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Manny Knowles (Member # 1171) on 06-12-2002, 12:16 PM:

Oscar:

I asked the manager to double-check the model number and it is indeed a DA-8.

Is the hum a "known issue" in this model? In other words, will I be wasting time/money by rewiring?

Also...Where can I get more of the Phoenix connectors for the Smart DA's? Are they generic?

Posted by Oscar Neundorfer (Member # 458) on 06-13-2002, 08:02 AM:

Manny,

The DA-8 was not particularly noisey in terms of hum, although it could have something wrong with it. Since it used resistive isolation, it was not as good at reducing hum due to ground loops as the DA-226 is with the transformer isolation. Is the hum present in ALL screens connected to the DA-8? If so, the DA-8 could have a problem. A test would be to remove all outputs from the DA-8 except for one and then check that one cinema to see if the hum is still present. If it is still there, then the DA-8 probably has a problem. If not, then there might still be ground loops causing the hum.

The early DA-226 units used a connector made by Entrelec. It is gray in color. The later units used the green Phoenix connectors. We can supply either one you need. BTW, as long as you have the proper mating connector, cards with each type of connector can be used in the same DA-226. If you ever need to order a replacement card for a DA-226 it is a good idea to let us know which type of connector you have. That way we can send you the card that matches your mating connector already attached to your wiring.

If you need actual Phoenix or Entrelec part numbers, let me know. I am home at the moment, so I don't have the numbers here with me, but when I get to work a little later, I can get them for you.

------------------
Oscar Neundorfer
Chief Engineer
SMART Devices, Inc.

oscar@smartdev.com

Posted by Manny Knowles (Member # 1171) on 06-13-2002, 08:39 AM:

Thank you Oscar...I will check the color of those connectors and follow-up via email.

As for the DA-8...I have more information that may mean something to you (or others present on film-tech) in terms of knowing what the problem is.

The DA-8 is mounted in the rack for Theatre #1. In that auditorium, the hum is present but not overpowering; you can hear it a little bit during silent or quiet passages on a CD.

Over at Theatre #2, the hum is a little louder. It gets louder as we move further away from the DA. Down in Theatre #5 we hear more noise than signal. It's just a razzy sounding hum.

[Edit: since we're now on page 2, I'll just remind everyone reading that this entire Non-Sync system was wired using computer cable...probably Cat. 5 Ethernet cable]

Posted by Gordon McLeod (Member # 33) on 06-13-2002, 09:23 AM:

Cat5 if used is totally inapropriate as it is non shielded. I would really doubt thzt is what was used (I hope)
It is interesting that a quad twisted pair cable and good balancing transformers can transmit hum and noise free audio under some conditions.

Posted by Manny Knowles (Member # 1171) on 06-13-2002, 09:53 AM:

Gord: That's why I kept mentioning the wire, because just by looking I could tell that it wasn't really the right wire. Certainly it is computer wire of some sort.

I'll make a note of the jacket markings on that wire next time I'm there.

Posted by Brian Tristam Williams (Member # 1235) on 06-13-2002, 03:11 PM:

Guys, thanks for the replies.

I know that you can get amplification UNITS from DA distributors. However, I don't want to sit around and wait for imports. What I want, if anyone can point me to it, is an amplification CIRCUIT - one that I can put together myself with common electronic components. It will also save a few pretty pennies.

Thanks.

Posted by System Notices (Member # 2357) on 01-20-2012, 10:31 AM:

It has been 3507 days since the last post.

Posted by Alban Birch (Member # 4121) on 01-20-2012, 10:31 AM:

Hi

We're going to wire our Background-music all together and thinking of purchasing the Component Engineering or the Odyssey distribution because of the daisy-chain method.
2 Questions:
since the source is in the middle of the booth, is it possible to run 2 wires in opposite directions?
do we need the receivers on basis-processors as they have balanced inputs?
Thanks and have a nice Weekend

Posted by Gordon McLeod (Member # 33) on 01-20-2012, 03:59 PM:

I have never liked the daisy chain method try to get a USL or a used Smart DA

Posted by Harold Hallikainen (Member # 5405) on 01-20-2012, 10:23 PM:

From my work in broadcasting for many years, I'm a big fan of balanced audio lines. The CD player probably has an unbalanced output and the processor probably has an unbalanced input. With a long line, this is asking for ground loop hum. Something like this ( http://www.henryeng.com/matchbox.html ) could be used both at the CD player and at each processor. At the CD player, the unbalanced high impedance output would be converted to low impedance balanced where it could drive twisted pair cable to each destination (daisy chain would be fine). At the processor, another MatchBox would bridge the balanced line and convert it to unbalanced suitable for driving the processor NS input.

Harold

Posted by Alban Birch (Member # 4121) on 01-21-2012, 05:49 AM:

What's not OK with the daisy-chain method? I prefer the idea of only pulling half of the cable. I'm uncomfortable wth 400ft of unbalanced low-level signal.
If somebody wants to get rid of said units or wants to make a quotation with delivery to europe, drop me a PM

Posted by Tony Bandiera Jr (Member # 2365) on 01-21-2012, 11:46 AM:

quote: Alban Birch
....... I'm uncomfortable wth 400ft of unbalanced low-level signal......

As you should be.

One thing I haven't seen mentioned yet in this discussion is that the SMART DA (and perhaps the USL) actually amplify the signal before sending it out, to help combat cable losses and improve the signal to noise ratio.

And if you put a request into the "Equipment Wanted" forum I am sure someone will come up with a Smart or USL unit for you. And if you end up with a Smart, I have 4 output cards you can have for postage cost. [Big Grin]

quote: Harold Hallikainen
.....Something like this ( http://www.henryeng.com/matchbox.html ) could be used both at the CD player and at each processor......

Harold, no offense, but that is just crazy in terms of cost ($225 PER UNIT) and I also did not see any mention that you could feed several units from one. Have you done it and how did it work out?

Also the specs, while fantastic, are total atomic overkill for non-sync.

Having said that, I will give you sincere thanks for that link as those units would be very handy (and cost-effective) for a variety of other uses. They just aren't, IMHO, the right solution for multi-point distribution.

Now here's another option: Component Engineering's AD-1 system.

LINKY

I have used these in 20-plex complexes with great success, and they are meant to be daisy-chained which saves a TON of wire. [Smile]

And each AD1-RX (the receiver end) has individual channel level adjustments so you don't have to run back to the master rack to set levels in any given auditorium.

I forget the cost (been a while since I used them) but they were pretty reasonably priced. (And they are still available.)

Posted by Alban Birch (Member # 4121) on 01-22-2012, 03:02 AM:

Thanks
Ii I would use the Component Engineering or Odyssey, could I wire the signal directly into the QSC Basis, as these have a balanced input?

Posted by Tony Bandiera Jr (Member # 2365) on 01-22-2012, 12:46 PM:

Alban, generally speaking, to wire an unbalanced output like the CE's to a balanced input, you would use a short cable (no longer than say 5 feet or 1 metre) and wire as follows:

Pin 1 of balanced input, tie to Pin 3, connect to the ground/shield of the unbalanced output;
Pin 2 of balanced input to the Signal/+ of the unbalanced output.

Those instructions apply if Pin 2 of the Balanced input is + (or "hot"). If Pin 3 is the + or "hot", then swap Pins 2 and 3 in the above instructions.

Posted by Alban Birch (Member # 4121) on 01-22-2012, 01:22 PM:

I thought the CE uses balanced transmission to the receivers

Posted by Tony Bandiera Jr (Member # 2365) on 01-22-2012, 01:37 PM:

It does, but the output of the receiver (which is what you need to tie to your BASIS system) is unbalanced.

Be warned: you cannot, with the CE system, try to directly connect the output of the transmitter to your non-sync inputs!! It is an amplified, constant voltage signal and you WILL damage your inputs, the transmitter, or both.

The lines between the CE transmitter and any and all receivers, are of course balanced lines and need to be wired as such.

Posted by Alban Birch (Member # 4121) on 01-23-2012, 12:35 AM:

Thanks Tony
That's the answer I've been looking. So I can't spare any receivers, except running the non-sync into one Basis and then transfer it over CobraNet to the far end of the theatre where the other two booths with Basis-processors reside

Posted by Mark Hajducki (Member # 1732) on 01-23-2012, 07:49 AM:

With the move to digital cinema, are any of the systems able/used to provide the non-sync audio?

Posted by Frank Angel (Member # 248) on 01-23-2012, 10:57 AM:

Or....you can try totally wireless. Use a Rocketfish transmitter/receiver -- it works on 2.5G transmission, gives you CD quality, and depending on your booth setup, you may only need a few of them, daisy chaining them and using additional transmitter to retransmit where the signal gets lost due to distance. Their range is 150ft transmission (of course given manufacturer's BS, that probably means 100ft). So you probably could get away with using one of the xmitters to feed three, maybe even four screens, then stick in another transmitter.

Ground loop problems would be no-existant, but you would have to see how booth EMI affects them, if at all. For a list price at around $70 (but I have seen them on ebay and amazon for $30-$40) it certainly is worth giving them a shot. Clicky here. Even if the booth is huge, you could locate your CD player and the transmitter in the center and get coverage end to end. And if not, if you wanted the CD player to be located at the server, say at one end, multiple transmitters as repeaters would extend the range.

This may be a stupid question, but why can't the CDs be uploaded, or "injested" as they say, into the server and programmed exactly like you program the trailers and the feature -- as program lists, but just audio, no image. OR better still, use one of those visualization computer programs to create synchronized color patters to project on the screen (make up for that ugly lack of a curtain) along with the music? Shouldn't a digital server be able to incorporate audio files as any other playable item in a play list? Seems like having a separate CD player and stringing separate wires to each screen system is down-right primative given that you've already got a complete audio/video server playback system designed specifically as a master AV distribution center to feed each booth's projector and audio system. Why even need to switch to external non-sync? Why is there even such a thing as an outboard "non-sync" when you've got digital servers?

Posted by Dave Macaulay (Member # 813) on 01-23-2012, 11:55 AM:

Using a server for non-sync is possible but it doesn't fit so easily into the scheduling model: you would have to start the "show" way early with the walk-in music as the first show element. Not a big deal I suppose. Doremi's TMS allows you to set a preshow duration, and then it backtimes the individual server starts from the scheduled showtime pulled from the ticketing system. Probably the other TMS/LMS systems do too; without a TMS you would have to do this adjustment yourself when entering schedules or doing manual starts.
Packaging the music for playback might be an issue. I haven't tried but I don't think the server will play a show element that isn't packaged properly - you can't just ingest an mp3 and play it, you have to create a proper DCP package... maybe this isn't rocket science but it isn't trivial.
Do the "movietunes" people supply walk-in server content packages?
Then what do you do with the lobby? Usually the same music plays in the lobby and as nonsync in all auditoria, all from the same CD player.

Posted by Scott Norwood (Member # 30) on 01-23-2012, 12:03 PM:

It would be pretty trivial to make a DCP with just the music track, but I have been told that some servers require both picture _and_ track in a DCP (even though this is not actually required by the specification), which means that one would need to make a picture track of all-black frames, which would make for a very large DCP.

This would also probably screw up some automation functions (because the automation system will sense that the show is playing, even when it isn't), as well as the timing of show starts.

The servers really should have a separate "non-sync music mode" where they can play WAV or MP3 or <insert favorite audio format here> files loaded into a separate playlist without activating the "show running" mode of any automation system that happens to be installed. The Dolby server does not have this function...I don't know about the others.

But a $99 CD player is still easier to use and more flexible, especially in a rental situation when the renter of the theatre waks up with a CD and wants it played as walk-in music.. The whole distro amp/hum issue could be solved if the processor manufacturers would use balanced connections for non-sync connections.

Posted by Alban Birch (Member # 4121) on 01-28-2012, 04:42 AM:

Hi
I thinkwe're going to do it with the odyssey.
The source and transmitter will be in booth 4 and from there we're in two opposite directions, this should be possible?
Do we need a receiver in booth 4 or could we just split the signal from the source to the transmitter and JSD-80? Maybe even use the SPDIF from the source to the JSD-80 of booth 4?

Posted by Harold Hallikainen (Member # 5405) on 02-10-2012, 05:02 PM:

I posted info about the Henry Engineering interface previously. As others have pointed out, it's a bit expensive. I just learned of a similar product at a lower price. It's at http://www.mcmelectronics.com/product/MCM-CUSTOM-AUDIO-555-8485-/555-8485 .

Harold

Posted by Tony Bandiera Jr (Member # 2365) on 02-10-2012, 05:15 PM:

Harold, not bad, another useful product, but NOT for this application!

Why the hell is everyone trying to re-invent the wheel here? There are ESTABLISHED, PROVEN distribution systems at reasonable cost. Smart (probably have to find used), Odessey, Component Engineering ALL make/made systems that work, are easy to wire and immune to noise.

The labor costs of trying to adapt an unproven system to this application, not to mention the cost and hassle of RETURNING gear that didn't work, makes this a beating of a dead horse.

Get the right gear for the job, put it in and be done for crissakes.

Alban, yes use a receiver for your source booth #4. Trying to split the signal ahead of the system defeats the whole idea of isolation which is what you need to make this work.

Posted by Harold Hallikainen (Member # 5405) on 02-10-2012, 07:15 PM:

Thanks for the comments! Again, I come from a broadcast background where balanced lines and bridging audio inputs are very common. So, this is the way a balanced audio line is distributed in a radio or TV station. I thought it would also be applicable to cinema, but, as you point out, other solutions are available.

Again, thanks for the comment!

Harold

Posted by Tony Bandiera Jr (Member # 2365) on 02-11-2012, 02:06 PM:

Harold, I would appreciate a direct answer to one question:

In broadcast, do they do what we're trying to do here, which is transmit ONE source to multiple remote locations? (and up to 20 like a cinema would?)

My limited experience with broadcast (CBS Studios) has only exposed me to the need to transmit a source or sources to ONE remote location, not daisy-chaining or paralleling to multiple remote locations.

And my point is that why try to re-engineer something where cinema-based companies have already done all the legwork? It just does not make sense to me to take that risk. And no offense intended to Alben, but it sounds like he either has limited technical background or does not have ready access to an experienced technician, which would make any "experimental" attempts extra risky.

He needs a straightforward, easy to install system with detailed instructions to ensure success.

If I were in his country I would gladly go help him with this.

Posted by Gordon McLeod (Member # 33) on 02-11-2012, 07:50 PM:

One of the big problems was at many event was providing isolated feeds to mulitple news groups and it was always done with direct boxes and some form of distribution amp
Op Amp Labs for years made a popular one

Posted by Carsten Kurz (Member # 5396) on 02-11-2012, 08:45 PM:

I would do it with active DI-Boxes. Most DI Boxes have loop-through outputs. Very easy to daisy chain them and have a single wire running from source to all processors. All balanced. Very easy to transfer balanced audio over CAT5 cables.

That said, the best solution certainly depends on the existing cabling or effort needed to rewire.

A simple autostart MP3 flash player today costs 60-100 US$. Could be cheaper and easier to assign one to each screen locally, instead of purchasing a distribution system and rewiring.

I guess it's not always the right thing to have the same audio at all screens.

- Carsten

Posted by Harold Hallikainen (Member # 5405) on 02-12-2012, 12:56 AM:

Quick answer to Tony... In broadcast analog audio, they used to use 600 ohm sources and 600 ohm terminations in point to point audio circuits. That's still done on very long circuits (many miles through telephone lines in the places this has not been converted to digital). In the 600 ohm days, distribution amplifiers were used to drive separate balanced lines out to each 600 ohm terminated load. Later, they moved to low impedance outputs (50 homs or less) and "bridging" inputs (typically 10k). So a single source could drive MANY bridging inputs.

I have no objection to the various other methods presented to resolve the issue. The use of these unbalanced to balanced converters is just one way to deal with it. To me, the big thing is to use balanced lines. Differential or transformer balanced inputs will subtract out the common mode noise (normally power line hum).

Thanks!

Harold

Posted by Tony Bandiera Jr (Member # 2365) on 02-12-2012, 12:51 PM:

quote: Harold Hallikainen
In the 600 ohm days, distribution amplifiers were used to drive separate balanced lines out to each 600 ohm terminated load. Later, they moved to low impedance outputs (50 homs or less) and "bridging" inputs (typically 10k). So a single source could drive MANY bridging inputs.

Ok, thanks Harold, that explains it better. If I am reading this right it sounds like the 600ohm system would be wired in a "home run" type setup, with each load line running individually back to the source, correct? Whereas the later system of 50 to 10k ohms could be wired as a single line with taps off it or as a daisy chain. (Which would be equivalent to the non-sync distribution systems we are discussing.)

I worked for Knott's Berry Farm in their tech department and we had some lines which were a few miles from the source for park-wide audio (the music and announcements) and they were all home-runned to a central audio room. They were 600 ohm balanced (mono) lines.

I heard but have not confirmed that they have now gone to a digital based distribution system using fibre optic or CAT6 cable and now do stereo.

[Big Grin]

Posted by Harold Hallikainen (Member # 5405) on 02-12-2012, 01:37 PM:

You've got it! This low source impedance and bridging loads works well for a few thousand feet. With really long lines (phone company provided equalized analog lines), the lines are driven and terminated with a low impedance. It was fairly common to drive and terminate with 150 ohms. The use of the lower impedance (as opposed to 600 ohms) causes more attenuation of the lows which brings it close to the attenuation of the highs. This reduces the amount of equalization required on the line.

As I think about it more, even for very long lines, we should be able to drive with a low impedance and have multiple bridging loads (10k) along the line with a low impedance termination at the end of the line. This is the way RS485 data lines work (low impedance transmitters, high impedance receivers, terminations at ends).

Interesting discussion. Thanks!

Harold