View Full Version : wireless audio


Pete Cofrancesco
March 20th, 2017, 03:19 PM
For a theatrical job I have a client giving me line via RCA that I will plug into my (correction) Sony UWP-D11 bodypack with rca Y to mini cable which the will be sent into my camera's left channel.

How does stereo get handled with this setup? I noticed the bodypack lav mic has a stereo jack even I'm sure it's a mono mic and these type of transmitters send a mono signal.

Can someone educate me on how stereo is handled by these devices.

Rick Reineke
March 20th, 2017, 04:52 PM
An RCA output is fo'sure unbalanced and line level.. however, some mixers just route the signal from the main balanced +4 outputs, so it could be higher than -10dB, so make sure the transmitter can handle it or some attenuation will be needed. l also don't know the Sony's input plug wiring, it could just short out everything out if the wiring is not 'right' I would test the set up before hand.
What input connection does the camera have? If if's an XLR input , it would probably be better to use a DI and feed the cam and transmitter mic level.

Jay Massengill
March 20th, 2017, 05:11 PM
Did you mean the UWP-D11 system with the UTX beltpack transmitter? I have the UWP-D16 with the beltpack and plug-on transmitters.

I don't know the exact connections in the beltpack transmitter jack, but one of the conductors is for power required by the lav element when the input is set to MIC Level.

You can set the input level in the menu to Line, but I haven't seen the exact connections listed anywhere to use, or if Sony has a ready-made line input cable for the beltpack transmitter.

I've only done this with the plug-on transmitter because it just uses a standard cable after setting Phantom Power to OFF and the Input Level to LINE.

These systems can't transmit stereo with a single set of 1 transmitter and 1 receiver that I know of.

For transmitting stereo line-level, I would use one of my Wi digital stereo transmitters as long as both the range and other 2.4gHz traffic was sufficiently low to be 100% reliable. Unless it's just for guide audio that is used for sync and will be replaced later. In that case, some dropouts are ok.

Richard Crowley
March 20th, 2017, 06:22 PM
For a theatrical job I have a client giving me line via RCA
Do you mean ONE RCA (implying monaural), or TWO RCA (implying stereo)?

that I will plug into my Sony UWX-D11 bodypack with rca Y to mini cable
What is the "Y" for? Are you taking Left channel on RCA, and Right channel on RCA and summing them together into monaural?

which the will be sent into my camera's left channel.
How does stereo get handled with this setup?
It sounds like you don't want stereo if you are recording on only one channel of your camera.
Making many assumptions in the absense of clarifying detail, it sounds like you are combining a stereo source into monaural using a "Y" adapter (or cable?)

I noticed the bodypack lav mic has a stereo jack even I'm sure it's a mono mic and these type of transmitters send a mono signal.
No. The bodypack transmitter has a monaural input because it is a monaural transmitter (and receiver). It may have a TRS connector for the input, but TRS does NOT mean "stereo".

Can someone educate me on how stereo is handled by these devices.
We still don't know what you mean by "handled"? We don't know what you are trying to do here?
If you only want to record monaural, you are already creating monaural (presumably) by taking stereo line-level signals and combining them together in a "Y"-something. Note that is generaly NOT an acceptable way of combining signals together. But it often works good enough for casual requirements.

If by "handle" you mean that you want to record stereo to your camera, then you must use some method that allows transmission of BOTH Left and Right signals. A monaural wireless system will handle ONE channel. So if you need wireless, then you must use TWO wireless systems. Or, of course, hard-wire the connection with two cables (or a stereo cable).

Pete Cofrancesco
March 20th, 2017, 07:41 PM
Common practice for dance recitals is instead of playing the music from the sound booth it's done off stage with consumer cd/stereo thus the rca.

In this particular case I'm covering the job for another videographer who told me wants the stereo feed that will be coming from two rca outputs.

So the goal is to combine the stereo using a y cable to mono mini to plug into a wireless bodypack that will send the music to one of the channels of my camera. A shotgun mic will got to the other channel.

I was curious why the cables adapters that come with wireless transmitter/receiver have mini jacks that have the same rings as stereo jacks ie they look exactly like stereo head phone jacks not mono. I use the number of rings on a jack to identify if it is stereo.

Jay Massengill
March 20th, 2017, 09:22 PM
The two cables that come with the set are for the receiver output.

One cable is mini to XLR male and the other cable is mini to right-angle mini.

The right-angle mini is specified in the manual to connect to the recorder input and the straight mini connects to the receiver output.

What camera will you be using? How far away will the camera be from the stage?

Is it intended that the combined stereo signal that's recorded to one channel of the camera will be guide audio to be replaced later with the actual playback audio files or will it be used as the "actual" music in the edit with the shotgun mic as the ambient?

Richard Crowley
March 20th, 2017, 11:50 PM
... wants the stereo feed that will be coming from two rca outputs.

So the goal is to combine the stereo using a y cable to mono mini to plug into a wireless bodypack that will send the music to one of the channels of my camera. A shotgun mic will got to the other channel.
Using a Y-something is not a "proper" way to mix two signals together. Although it often works "good enough"

I was curious why the cables adapters that come with wireless transmitter/receiver have mini jacks that have the same rings as stereo jacks ie they look exactly like stereo head phone jacks not mono.
They have two rings because they accommodate both mic-level and line-level signals. And because they accommodate both audio signals and microphone power. Exactly how the TRS is wired depends on the make and model of the body-pack transmitter.

I use the number of rings on a jack to identify if it is stereo.
That is not reliable. And your case is an excellent example. Chances are that the tip of the TRS connector is meant for the monaural microphone and has a power voltage applied ("plug-in power" ~5V) and the ring may be for the line-level input. At least that is the "pinout" for Sennheiser TRS connectors.

I didn't find similar pinout information for Sony with a brief search. There is apparently a line-in cable for the Sony transmitters. EC-1.5BX although there appears to be no details about it online. So it is not even clear whether it is wired for mic-level or line level.

It is also confusing that the model number you cited ("UWX-D11") does not appear to be a valid Sony product number. The closest Google and Sony would admit to is: "UWP-D11"

Pete Cofrancesco
March 21st, 2017, 05:49 AM
Richard my mistake it's UWP-D11. It can be set to mic or line input.

I see what you're saying the segments of a TRS can be used for different purposes. For headphones the Tip and Ring is for stereo where as in my application its for balanced mono.

I figured things out. I ran a test and discovered when a stereo signal is plugged into the transmitter, it discards the right channel and sends only the left.

Don Palomaki
March 21st, 2017, 07:36 AM
Using simple "Y" adapter to mix stereo channels to mono is a kludge at best that relies on the output impedance of the source being sufficient to prevent overloading by the left-right cross connection. Not a good idea for low impedance sources.

Read the manuals for cautions, especially relative to the head phone output of the receiver. It appears to use a 3-contuctor (TRS) mini-phone for use with stereo headphones, but is mono output, and use of a 2-conductor plug will short the output.

...wants the stereo feed that will be coming from two rca outputs.

Are you sure he doesn't want a stereo audio track (music). An alternative is to to get a copy of the music (tape, file, or CD) and mix it in later. But that involves more effort.

Is there an announcer or MC involved that needs to be recorded as well?

For information, the following link claims to show the mic connector interface equivalent:
https://www.google.com/search?q=BMP+connector+pinout&tbm=isch&imgil=NGk27-ZsvIlZYM%253A%253BW1VHxk4Fpcf2UM%253Bhttp%25253A%25252F%25252Fwww.dvxuser.com%25252FV6%25252Fshowthr ead.php%25253F86425-Wiring-diagram-for-BMP-type-(Sony-wireless)-mic-connector&source=iu&pf=m&fir=NGk27-ZsvIlZYM%253A%252CW1VHxk4Fpcf2UM%252C_&usg=__lcpREbwevXw0xURYnx5n96TI_Bw%3D&biw=1240&bih=719&ved=0ahUKEwjN79aF2-fSAhWrwFQKHRRKAjcQyjcIJw&ei=rSvRWI3lFKuB0wKUlIm4Aw#imgrc=NGk27-ZsvIlZYM:

The transmitter bodypack appears to use the tip for audio, ring for DC power, and sleeve for ground return. Not a balanced input, but for short runs that is usually OK.

While it might not exactly match what is in the UTX, it can be used as a guide to help avoid problems. It clearly indicates that there would be risks involved in connecting some other non-BMP MIC source to the bodypack input with simple adapters not configured for the bodyback's design.

Jay Massengill
March 21st, 2017, 08:00 AM
A better way to mix a stereo signal to mono is to use a mixer, either panning the two inputs together or sending both of them equally to a post-fader Aux Send or a Group Output.

In any case, if some or all of the music is not mono compatible (due to oddity in the original mix or error in editing the music for the specific dance number), then there will be problems with the signal if mixed to mono through any method.

If it's just for guide audio to the camera and you don't have a mixer to place at the RCA outputs, I would only use one of the RCA outputs and send that to the camera. It's sufficient for sync purposes if you replace that "music" with the actual playback files later. Replacing later is more work but sounds much better. When it wasn't critical but was still going to be used as is, just one channel of the music is sometimes sufficient. It depends on the specific songs used.

Hopefully all sources, such as the MC mic, will appear equally at these RCA outputs that you have access to.

It needs to be tested with a multimeter if the Mic Power on the Sony beltpack transmitter input is automatically switched off when the input level is changed to Line. Otherwise that could also cause significant noise problems with the input signal or damage the transmitter input itself being shorted with the wrong cable.

You could use a wide-ranging-attenuation passive direct box like the Rolls DB25b, RCA to TS 1/4-inch male adapter cable and the Sony EC-1.5BX input cable to connect to the beltpack transmitter. That would be the most simple, safe and easily adjusted way to do it.

Pete Cofrancesco
March 21st, 2017, 11:53 AM
Thx Jay getting the Rolls DB24 seem like the safest and most appropriate solution.

Don getting the original audio that doesn't work for a number of reasons. The most important is the music isn't played continuously, it's started and stopped for each dance. So you would be spending hours in post syncing 40+ songs.

Jay Massengill
March 21st, 2017, 01:38 PM
I hadn't seen the relatively new DB24. Let us know if you have any oddities with the music signal when summing to mono, and how it goes with interfacing to the beltpack transmitter input.

I replace and sync about 45 songs for our dance recital. It does take a lot of time, but only because it's a lot of material. If you have a good guide track all you have to do is match the waveform start for each, it's easy depending on which software you use. And I'm going for maximum quality since I'm personally invested in the outcome.

Steven Digges
March 21st, 2017, 02:13 PM
I figured things out. I ran a test and discovered when a stereo signal is plugged into the transmitter, it discards the right channel and sends only the left.

One more problem to mention here. Music is often mixed with some of the sound (vocals or instruments) sent to just one channel to emphasize stereo effect. Or for what ever reason was in the mind of the producer at the mix. Discarding one channel means you could be discarding essential beats, music, or vocals.

This is nothing new, a good example of this mixing is the old classic I Feel Good by James Brown. The trademark opening line of the tune when he screams I feel good is only on one channel (right, if I remember correctly). If only the left channel is played you will barely hear the words at all. How do I know that? Those three words were a critical Que as part of a client show. I got burned when it turned out the FOH mixer sent only the right side out of the mixer and daisy chained all PA speakers. My bad, I was the TD and I know AV guys love shortcuts like that. I should have checked it.

So the Y is a bad idea. Why don't you just mic the speakers coming out of the box? I have never made a recording that way but the wedding guys do it all the time. Or put a recorder there, even if as a back up.

Kind Regards,
Steve

Pete Cofrancesco
March 21st, 2017, 02:45 PM
Good points. One caveat I'm filming this for another videographer who's double booked and is very particular on how he wants it done. It's not my place to disregard his instructions it's his client and he will be editing it.

I'm mainly asking these questions to better educate myself.

Colin McDonald
March 21st, 2017, 03:28 PM
Why don't you just mic the speakers coming out of the box? I have never made a recording that way but the wedding guys do it all the time. Or put a recorder there, even if as a back up.

Is there any chance of doing that plus getting a copy of the CD(s) - then he can use the mic recording as a reference and sync up the much better audio from the CD(s) later.

I've managed to persuade bands to part with copies of unreleased singles in the interest of getting decent audio on videos from a promo tours. Where commercial CDs have been used I just got a copy (and made sure someone else dealt with the copyright :-)

Richard Crowley
March 21st, 2017, 09:11 PM
I figured things out. I ran a test and discovered when a stereo signal is plugged into the transmitter, it discards the right channel and sends only the left.
Yes, that is because your unidentified "Y-thing" is apparently a "stereo breakout" adapter which assumes Left=Tip and Right=Ring. But since we have established that the TRS input to your transmitter is monaural, it is no surprise that it is getting only the Left side of the stereo signal. So you aren't really combining L+R, you are simply connecting Left to the transmitter and discarding the Right channel.

Pete Cofrancesco
March 21st, 2017, 11:08 PM
Yes, that is because your unidentified "Y-thing" is apparently a "stereo breakout" adapter which assumes Left=Tip and Right=Ring. But since we have established that the TRS input to your transmitter is monaural, it is no surprise that it is getting only the Left side of the stereo signal. So you aren't really combining L+R, you are simply connecting Left to the transmitter and discarding the Right channel.
My confusion was that I knew the wireless transmitter sends a mono signal and the guy I'm covering the job for is insisting I feed it a stereo signal with a splitter cable.

He's used this method for a long time and never realized he's just getting the left. I don't think I could convince him otherwise and if he's been happy with the results I'm going to leave it alone.

Richard Crowley
March 22nd, 2017, 12:12 AM
It seems quite possible that he was indeed combining Left and Right into Mono using a proper "Y-adapter". However, you appear to be using a "stereo break-out" adapter which physically looks identical to a "Y". But because of the way the input connector of the transmitter is wired, it is getting only one channel.

You could be right. But without much better detail about exactly what he was using and what you are using, there isn't enough information available here to conclude either way.

Pete Cofrancesco
March 22nd, 2017, 05:44 AM
The Y cable is something I found in my supply box. I'm not sure what I could tell you more about it. I can try to get a hold of his setup today but I have used it in the past and I believe its just a bunch adapters cobbled together.

Btw, would I need to convert an unbalanced input if my transmitter input is unbalanced?

Rick Reineke
March 22nd, 2017, 09:56 AM
"Btw, would I need to convert an unbalanced input if my transmitter input is unbalanced?"
- Not if it's unbalanced already.
OTOH, balanced to unbalanced ....or... unbalanced to balanced would need 'custom' wiring. Normally an XLR's pins 1 and 3 are tied together (or the ring and sleeve terminals on a 1/4" TRS).

Pete Cofrancesco
March 22nd, 2017, 12:02 PM
Looks like I got mixed up along the way, so I don't need it balanced.

So the two issues I need to address are:
1. To be able to attenuate if I'm receiving a speaker line level.
Jay recommend the Rolls DB25
2. To mix stereo into mono. Although I'm not sure there would be a big difference.
So is there a device that does both theses things otherwise you get a mess of stuff. I have Sound Device 302 field mixer but I'm not sure if its the right tool for the job.

John Nantz
March 22nd, 2017, 12:22 PM
My confusion was that I knew the wireless transmitter sends a mono signal and the guy I'm covering the job for is insisting I feed it a stereo signal with a splitter cable.

He's used this method for a long time and never realized he's just getting the left. I don't think I could convince him otherwise and if he's been happy with the results I'm going to leave it alone.
Pete - it gives me pain to read this.

Idea: If he isn’t one that’s easy to convince, assuming time and distance isn’t a problem, what about if you meet with him and either he gives you a connector(s) to use or he blesses something that you have?

And code it/them with tape.

I’m sorta like Steven a few posts up. Filled in to do a stage performance, did a trial shoot during rehearsal, the stage was too dark and there was a lot of grain. Showed the other videograper what it was like, told to go ahead and do it, put a lot of time into it, then was told it wasn’t good enough. This was several years ago and I haven’t forgotten about it.

Having everybody happy feels good. Being a fall guy is no fun.

Pete Cofrancesco
March 22nd, 2017, 12:48 PM
He no longer lives locally that's why I'm covering it. I also don't think it's a big deal discarding a stereo channel especially in this scenario. How many people watching a dance recital on their tv could tell the difference?

John Nantz
March 22nd, 2017, 01:44 PM
Yea, putting it that way, you’re probably right.

But remember another saying: “No good deed goes unpunished!"

Jay Massengill
March 22nd, 2017, 08:45 PM
I recommended using the Rolls DB25b for several reasons.

First, it has a wide range of variable attenuation from -20db down to infinite attenuation, and we really don't know what level the RCA connectors you have access to will carry other than it's some type of line level.
Usually that's -10db but as mentioned some mixers output much hotter than that on the RCA connectors.

We know the Sony beltpack transmitter can be set to Line level input, but I haven't read any specs on exactly how hot it can accept.

Second, the correct Sony cable (EC-1.5BX) for inputting Line level signals into the beltpack transmitter has a female XLR connector. Even though the connection into the transmitter is unbalanced, the DB25b would be an easy way to make this connection and have some variable attenuation if needed.

However, if you really want to combine both RCA signals, the DB24 you mentioned would do that using the Mono/Stereo switch on the back of the unit. It also has attenuation controls.

You would just need a cable with female XLR to the correctly wired mini TRS male end to go into the transmitter properly.

How much time do you have before this event? Can he describe exactly the cable he used before?

Paul R Johnson
March 23rd, 2017, 03:20 AM
This is just a bit silly, and making it far more complicated than it needs to be. Richard said it way back - you can parallel up a stereo output to make it mono. Ideally it should be done properly, but finding equipment that is bothered by this is rare. If you can solder, do it properly - join the two RCA connectors from left and right sources to produce a single unbalanced signal. If you can't solder, then you have to sacrifice a made up cable, and use block connectors with screw terminals (not sure of the US term) to route both to the same input.

The TRS connector on radio packs does get used to supply the +Volts on a separate pin, but some, like Sennheiser have the mic and the line level on the tip and ring. A guitarist buys the guitar lead that is connected to the line input, but the mics use the other input. The connector type denotes absolutely nothing!

If the prospect of recording just the left, or right worries you - and I guess that for most music, people won't notice - but if it was say a 70s big band recording, you'd be in trouble, or an early Beatles recording - because they panned hard left and right. So Glenn Miller style do-wop do-wop sax and trombones would mean it would either be wop or do, not both.

For dance shows, I always try to take with me their CDs, because then I always have the get out of jail possibility of replacing the room sound with the CD for emergencies.

Why not just make up an adaptor cable for stereo to Sony, and keep it in the toolbox?

Jay Massengill
March 23rd, 2017, 06:09 AM
I did find in Sony materials the beltpack transmitter input when set to Line level can take +4dBu.

I figured out a way to mock up this planned connection from two RCA's to the Sony beltpack transmitter using just two off-the-shelf cables and will test it later today if I have time.

Pete Cofrancesco
March 23rd, 2017, 07:50 AM
Thanks Jay take your time the job is a month away.

I can solder but I'll wait for Jay's off the shelf solution.

I noticed that even though the body pack's menu has an attenuate setting it can't be used when set to line.

One other note about songs that have a strong channel change. They would still be heard in the camera's other channel that is recording the ambient via shotgun mic.

Yesterday we couldn't find his setup but like I said I've used it previously and it was a series of off the shelf cable adapters connected to an ancient bodypack, so I doubt it mixed it down to a mono signal.

After reading Jay's post I realized I have the necessary equipment to pull off a single channel solution as follows:
Body pack > trs to xlr cable > xlr attenuater > xlr to rca cable

Paul R Johnson
March 23rd, 2017, 09:39 AM
That does the 'mono-ing' too?

Scrap the pile of adaptors, get the iron out and in ten minutes, job done and 100% reliable. No point over complicating this. Keep it as simple as possible.

Rick Reineke
March 23rd, 2017, 11:14 AM
I concur with Paul. Your asking for trouble with a bunch of adapters daisy-chained together, especially the low cost "Made in China" variety w/ molded on connectors. They break just by looking at them.

Jay Massengill
March 23rd, 2017, 03:27 PM
The test worked and required just two off-the-shelf Y cables and no adapters.

However, this should be the basis for making your own custom cable as it's an inelegant solution, but did prove the connection works for summing stereo to mono and connecting into the beltpack transmitter in my test scenario.

Cable #1 is a two-RCA male to one-RCA female Y cable. Connect it to the stereo RCA outputs you have available.

Cable #2 is a two-RCA male to mini TRS male Y cable. You will only use ONE of the RCA connectors, the one that connects signal to the TIP of the mini connector.

First set the beltpack transmitter to Line Level in the menu and then power it off again before making the connections.

Figure out which RCA connector of cable #2 connects to the tip of the TRS mini. Mark it, and connect it to the Female RCA of cable #1. (I had a cable that came already marked Tip and Ring on the RCA's.)

The other male RCA of cable #2 isn't connected to anything. I recommend covering it with an insulator. Don't tape directly on it, that will leave residue. Also don't cut that leg off, it could short the shield to the conductor at the cut and would also ruin the cable for normal use.

This unconnected leg could pick up noise, so use as short a cable as is practical if you must use this solution rather than making your own cable. I was in a pretty bad RF environment and using a 6-foot cable and didn't hear any problem since it was Line Level input. YMMV.

I recommend making your own custom cable with a single RCA male wired to the Tip and Sleeve of a mini TRS connector. The ring of the TRS mini is left totally unconnected.

This way you can use the custom cable alone if you only have a single RCA source in the future. If you need to sum stereo to mono, just add the commonly available Y cable #1 in my example above.

Don Palomaki
March 24th, 2017, 08:05 AM
Just an alternative thought. If the the shoot is far enough in the future you could always ask him to mail his adapter chain for you to use. That way you should be able to give him what he gets on his own. Just test it when you receive it to be sure it works.

Covering for guys who overbook is always interesting. Is he paying you, or is his client paying you, or is this a favor? In any case be sure you cover your liabilities. Some people can get squirrelly if things are not as they imagined they should be.