Picking Up Radio Signal on Sound Board RCA Cable

[Jason Robinson]

Originally Posted by Ty Ford

right. Do I remember correctly, you heard the AM during recording? I'm asking because some folks have said they recorded and didn't hear anything until playback.

Oh I heard it faintly in the background while recording.
House PA Mixer -> headphone jack -> 1/4" to 1/8" stereo adapter -> 1/8" to dual RCA -> RCA to 1/8" stereo adapter -> Beachtek -> beachtek to GL2 via 1/8" stereo -> GL2 1/8" stereo headphone jack to headphones.

I just have a cheap pair of headphones (the most expensive that Fred Meyer had was the $30 JVC HA-RX300) and I could hear it in the background just barely, but loud enough that I knew it would be on the recording.

Originally Posted by Ty Ford

and a stash of different gozinta and gozouta cables.

Is that a brand name? ;-)

Originally Posted by Ty Ford

Your audio guy should have them. I don't know what you currently use as a mixer, but a Sound Devices 302 mixer can cure a lot of these problems with its balanced transformer inputs. They help to scrape off the bad audio problems before they get to the camera.

Unfortunately my audio tech has always been employed using other people's gear and as such hasn't been able to amass his own stash of gozintas and gozoutas. ;-)

So essentially the job of the SD302 is to provide the ability to take nearly any kind of signal over XLR (line/ mic) and to provide ground loop isolation, phantom power if needed, and then send the signal in stereo XLRs to something else. My only mixer is the Beachtek DXA-8 mounted under the GL2 since I need everything camera mounted (I mostly do weddings and live run & gun events like that). I would love to have a SD302, but $1300 is far more than I can afford. But should business pick up (at what would have to be an exponential rate), I'll know what to get.

Originally Posted by Ty Ford

For your mixer to camera cable (if your camera has a stereo 1/8" unbalanced stereo input) I'd get a regular "balanced mixer to camera with headphone return" cable.

Would you use the headphone return cable instead of the headphone out of the camera? I like to make sure I'm hearing what the tape heard. I've never heard of a cable that also has a headphone tap in the cable (unless I'm misunderstanding what you are saying).

Originally Posted by Ty Ford

The camera ends will be male XLRs. Get two short female XLR to male RCA cables and a Y-cable with two mono female RCAs on one end and a male unbalanced 1/8" stereo TRS plug on the other.

Yep that part should be the easiest of the entire setup.

Thanks again for all your help Ty (and everyone else).

[Ty Ford]

Oh I heard it faintly in the background while recording.
House PA Mixer -> headphone jack -> 1/4" to 1/8" stereo adapter -> 1/8" to dual RCA -> RCA to 1/8" stereo adapter -> Beachtek -> beachtek to GL2 via 1/8" stereo -> GL2 1/8" stereo headphone jack to headphones.

>>>>>>Jason, I think you problem was the unbalanced mixer headphone output and your collection of unbalanced connectors.

Is that a brand name? ;-)

>>>>> No. :)

So essentially the job of the SD302 is to provide the ability to take nearly any kind of signal over XLR (line/ mic) and to provide ground loop isolation, phantom power if needed, and then send the signal in stereo XLRs to something else. My only mixer is the Beachtek DXA-8 mounted under the GL2 since I need everything camera mounted (I mostly do weddings and live run & gun events like that). I would love to have a SD302, but $1300 is far more than I can afford. But should business pick up (at what would have to be an exponential rate), I'll know what to get.

>>>>>>>The AM RF was not due to a ground loop. I have heard radio getting into balanced audio, but usually there's a weird wiring problem causing it. Neutrik makes a special set of XLR connectors with built-in RF killers that are the next line of defense.
Neutrik - Audio - EMC-XLR Series
If you're going to be around an RF saturated environment, you might want to make up some cables with these connectors.

>>>>>>>Ground loop noise is usually a buzz due to ground potential differences form two different AC outlets that you have gear plugged into. The 302 is a solid piece of gear with balanced transformer inputs that scrape off a lot of problems, but you can still get buzz if the camera is powered by one ac source and the house feed is powered from another ac source. You don't usually get ground loop buzz if both camera and mixer are on batteries, but I have heard it if an AC-powered video monitor is connected to the camera and the audio is coming from an AC-powered house feed.

Would you use the headphone return cable instead of the headphone out of the camera? I like to make sure I'm hearing what the tape heard. I've never heard of a cable that also has a headphone tap in the cable (unless I'm misunderstanding what you are saying).

>>>>>>>>Yes, a "camera hose" has two balanced XLR cables and a headphone return in one cable. It also usually has a multi-pin connector at the camera end so you can unplug one connector at the camera end and leave the "tail" plugged into the camera. You DO have to remember to reconnect. I listen to the return on my mixer so I don't get fooled. Everyone I know has made that mistake once. :)

Thanks again for all your help Ty (and everyone else).

>>>>>>>>>You're welcome. Regards, Ty Ford

[Carl Hayes]

Originally Posted by Ty Ford

If the two mics are different distances from the jukebox, the time delay will have to be compensated for for cancellation. In this scenario the room acoustics and system differences will mess with the two signals enough to make cancellation difficult at best.

Yes, the forensic guys have nice toys, but a lot of the CSI stuff you see on TV is still fiction. It's not likely that you'd be able to create an mirrored radio station interference signal to null the stuff on the tape you don't want. And the forensic guys aren't really concerned about fidelity, they just want to be able to hear what was said. That's different from trying to reclaim audio with any fidelity.

Regards,

Ty

Yes, the time delay, and the way to use the software features to compensate for it, are discussed at length in the instruction manual for the software (which I do have). There's extensive discussion in this very thick (over 1 inch) manual. More serious [I'm saying what I learn from the manual] are the differences in reverb, room acoustics, and the like, between the locations of the two mikes. One solution, (often used according to my friends who have done it) is to place two mikes on an operative (or informer). One mike is at about chest level to capture the forensic audio, and another is at the ankles to capture the reference signal that is to be subtracted. Once they had a fidgety informer who kept tapping her feet -- this was a drug case, and she was pretty cracked up herself -- and kicking the chair legs, which did not help.

And of course you're right -- they're after intelligibility, not musicality. Still, I'd like to play with this myself, and it is known to work.

Another application discussed in the manual is removing voice from accompanied vocals. If (and only if, according to the manual) the original mix placed the singer at exact center, probably a common practice, you can mix the two stereo tracks to produce a mono reference track, and then subtract this from each of the original two original stereo tracks to get rid of the vocal. I haven't done this either, of course, but with some of our modern "singers" -- I prefer Renata Tebaldi or Salli Terri -- it would be a good thing, eh?

But I fear my original post tended to give an impression that I have more personal experience than I actually have. That was not my intention. I am very experienced at cleaning up audio from old LP recordings, and have done a few 78s too, but all my knowledge of forensic audio processing is second-hand.

[Ty Ford]

Originally Posted by Carl Hayes

Another application discussed in the manual is removing voice from accompanied vocals. If (and only if, according to the manual) the original mix placed the singer at exact center, probably a common practice, you can mix the two stereo tracks to produce a mono reference track, and then subtract this from each of the original two original stereo tracks to get rid of the vocal. I haven't done this either, of course, but with some of our modern "singers" -- I prefer Renata Tebaldi or Salli Terri -- it would be a good thing, eh?

Yes, but.....anything panned center, (and bass and kick drum usually are), will also be canceled.

Regards,

Ty Ford

[Carl Hayes]

Originally Posted by Ty Ford

Yes, but.....anything panned center, (and bass and kick drum usually are), will also be canceled.

Regards,

Ty Ford

True, anything dead-center goes away. If what's in the center is "kick drum" that ain't all bad.

It turns out that this capability is in the non-forensic version of the software, and I have been playing with it today for the first time. The forensic version works in the frequency domain, which is why it doesn't require perfect time correlation, while the non-forensic version works in the time domain, and does.

Bass and kick drum? You and I listen to very different kinds of music, I guess. :-)

Anyway, I've removed Karen from the Carpenters' "A Kind of Hush" -- a shame, I really like Karen's voice and style, though frequently not her timing. It works! You can still tell she's there, just barely, but all you hear is the reverbs from her voice, not the direct.

I long ago corrected Karen's [in my view] poor timing in my own library of Carpenters music. Very nice, except for those who like her timing, which I guess many do, especially the sort who listen to "bass and kick drum".

Please understand, I say all this with a friendly grin, hard to present in writing.

[Steve House]

Originally Posted by Carl Hayes

....I long ago corrected Karen's [in my view] poor timing in my own library of Carpenters music. Very nice, except for those who like her timing, which I guess many do, especially the sort who listen to "bass and kick drum".

Please understand, I say all this with a friendly grin, hard to present in writing.

Hate to tell you, but the last time I heard that duo their accompaning band included both a bass and a drum set and most drum sets I've seen include a kick drum. In fact, I seem to remember a photo of the two of them on stage and behind them bold as life was a kick drum with "The Carpenters" in big letters across the drumhead. <grin>

[Carl Hayes]

Originally Posted by Steve House

Hate to tell you, but the last time I heard that duo their accompaning band included both a bass and a drum set and most drum sets I've seen include a kick drum. In fact, I seem to remember a photo of the two of them on stage and behind them bold as life was a kick drum with "The Carpenters" in big letters across the drumhead. <grin>

Yes, and Karen started as a drummer -- considered herself "a drummer that could sing a little". Since I often find her timing less than perfect, and nearly everything else about her performance very good indeed -- give or take a little reservation on attack/release -- I wonder how good a drummer she was. Isn't the drum nearly all timing? That's what I always assumed.

Richard, now -- gifted arranger -- that man's a MUSICIAN. I could never do that, not in a million years.

-- Carl