Last week I shot a multi-cam event for a school administration fall communication update to the parents. I decided to try something new on what would be a relatively stable and completely uninspiring shoot. I brought out the alienware and the shuttle computers and recorded live direct to the PC using Vegas, as well as recording to tape (just in case).

There were only two problems with the shoot....

1) The stupid "getting audio from venue PA system into cam with out the hum & hiss" problem
and
2) Accidentally moving the alienware and bumping loose the 1394 cable interrupting the stream for a few seconds.

This is the first time I noticed that I was picking up a radio station broadcast on my audio feed from the mixing board. The board headphones didn't have the signal, but phones plugged into the cam revealed the DJs talking, and some music, etc. Gahhh. Pretty much ruined my feed.

I couldn't get a line or mic out and as usual, the operators were not highly trained. They know which input was the speaker's lapel, and which was house speakers. And that was it. I tried and tried to get an AUX line on the system out to my cam's Beachtec, but it was useless. Nothing but buzz and hum and no audio signal. I obviously didn't know how to rout the mixer's output to that AUX bus.

But I could get a signal from the monitor headphone jack. I hated to do it because I knew the problem I was going to face. And sure enough. I got a signal, and could adjust the volume, but it was a dirty signal AND it was picking up the radio signal more than likely due to my cable linkage. I was using...

0) Sound board headphone jack
1) 1/4" to 1/8" adapter
2) 1/8" to RCA pair
3) 20ft RCA stereo pair cable
4) RCA pair to 1/8"
5) to Beachtek

So somewhere in that patchwork was where the radio signal was getting picked up. Now you will immediately ask "why didn't I use my 20' XLR cable that was sitting right there" and I would say.... because I don't have the adapter(s) to turn 1/4 stereo to mono XLR female (yes I know B&H has them and the next gig I book, I'm buying one for the $15 or whatever the cost).

And even if I did have it, would that eliminate the horribly dirty feed from the mixer's headphone jack? Not likely. It seems like Headphone jacks are way to hot (probably to drive the speakers in studio headphones) so I need some sort of limiter (yes the beachtek has built in ones, but they are not the best) and some sort of frequency filter to cut out the low end buzz / hum, if possible.

I've looked on here before (and through B&H), but I'm either not using the right search terms, or I keep missing it. Does any such device exist to clean up the audio signal? The only ones I've found use TRS jacks (must be a 1/4" jack that guitars & amps use).

First, probably be a good idea to get in there ahead of time to see what's going on in terms of your audio feed. You had a mixing board. Just knowing that, you were most likely to have a clean feed to use. A little planning, and you would have been easily on your way!

I'll agree, the headphone amp was not a clean way to go.. that is an issue in itself.

Next, your cabling was poor. Frankenstein'ing adapters is a way for rf noise to seep into your line. On top of that, you're using RCA cables which are unbalanced. To make matters worse, you were using 20 ft of it.

All you really needed was proper XLR or TRS cables and a little planning before hand.

All you really needed was proper XLR or TRS cables and a little planning before hand.

So is a TRS the same as a 1/4" stereo cable? I assume a TRS is actually a mono cable that provides power (like for amps, etc). Is it shielded to prevent picking up the radio?

If I have the 1/8"mini jack to XLR adapter (with the 1/4to1/8 adapter in front of it) would that eliminate the chance of picking up the radio station?

The 20' cable was mostly needed to get the audio from the mixer to the cam. I could have probably made do with a 15' cable, but anything short would involve hopping over the cable.

Even if I could get the AUX8 bus to get a feed from the lapel input (this was a massive ~30 input digital mixer) wouldn't that AUX output have been a line levels instead of mic levels? I'm not sure if just bringing the gain down on that would be enough (though feel free to correct me if I'm wrong).

Secondly, on other location shoots I cannot be guaranteed a mixer that I am familiar enough with in order to fiddle with the mixer to find an AUX output, let alone be allowed to get one (especially if the audio tec doesn't know their stuff and won't allow me to poke around behind the mixer). That leaves me resorting to the headphone jack again and putting up with a dirty signal.

you could of taken a XLR Y cable and split the main outs. most boards have 1/4" and XLR outs so maybe you could of used one of them if they were empty. you also could of used the TAPE outs too.
I've used a headphone jack in an emergency. works if the output is turned down and camera set to LINE level. not the best, but it works. most likely it was the RCA cable that did you in.

while not cheap, a audio isolation transformer is a life saver for these gigs as it will eliminate ground loops with the board. imagine doing a truck gig taking 12 feeds from the house board and putting a transformer on every connection.... but it saved the day

time to get a set of decent adapters.

The unanswered question in your posts was if there is anything that can clean up the audio.

I will start by disclaiming: I have not "personally" used this product and do not own it (yet) but the online demo of "SOUNDSOAP 2" was impressive indeed. May not solve all your problems but could help... the lower end version is $129, and the Pro version is $400.... but it amazed me what it could do. (I found it by looking for a way to counter the noise of a 16mm film camera... and when I saw what it could do there I was hooked....their website has a great little video that demonstrates its capabilities... I joked recently on a shoot there is no such thing as an airplane noise filter, but by gosh, maybe there is !)

Google it and check it out....

I'll disagree with some of what's written above.

The basic problem is unbalanced cabling. "Converting to XLR", suprisingly, doesn't neccessarily get you into the world of balanced signals. For that, you need to have a balanced output and balanced cabling to your beachtek. And most beachteks can handle line levels.

If you can get a proper balanced XLR or TRS output from the board and can keep that balanced to your beachtek that's it - you're done.

If you have to use an unbalanced output you have two "best practices" choices. Keep the cable short, no more than 6', or, use a passive or active direct box aka. DI to balance the output... again with a very short unbalanced run from the board output to the DI.

Once you're truly balanced, you can run a few hundred feet.

TRS, like XLR, is just a connector with 3 conductors. The magic happens in the board output and the beachtek input circuits. The 3 conductors are signal, ground, and -signal. When RF strikes the cable, it will tend to affect the signal and -signal oppositely. The balanced input magically sums the two signals in such a way that the RF mostly goes away.

Just a note, balanced circuitry and cabling is half the long-cable solution. The other half is low impedance. A high-impedance output -> input will tend to lose some of the high frequencies over longer distances. Probably more than you wanted to know, the rule of thumb is 6' of high-impedance or a couple hundred feet of low impedance will not significantly degrade the higher freqs.

Of course there are exceptions to that, too...

A search on this forum on the term direct box or di will turn up more information - you're not the first person to experience this.

The unanswered question in your posts was if there is anything that can clean up the audio.

I will start by disclaiming: I have not "personally" used this product and do not own it (yet) but the online demo of "SOUNDSOAP 2" was impressive indeed. May not solve all your problems but could help... the lower end version is $129, and the Pro version is $400.... but it amazed me what it could do. (I found it by looking for a way to counter the noise of a 16mm film camera... and when I saw what it could do there I was hooked....their website has a great little video that demonstrates its capabilities... I joked recently on a shoot there is no such thing as an airplane noise filter, but by gosh, maybe there is !)

Google it and check it out....

Software solution would be nice, but I'm trying to eliminate as much POST work as possible (since that takes me much longer to perform). I will keep that in mind though.

I do have Sound Forge and the NR plugin & the VASST audio cleanup tutorial DVD (which has helped immeasurably for getting rid of the buzz & hum on other projects and I'm sure will on this one). But a software solution is still pretty dang time consuming.

Okay.. I thought you had already recorded what you could and were faced with "fixing it". If not, then my post was more or less irrelevant, sorry.

Still ...a pretty unique product, I recommend you investigate it as a backup plan in the future. Way!! more than a clicks and buzz fix. It can memorize a noise and remove it. (like a motorized camera running for example... which is what led me to it.)

Could it have been a simple ground loop problem? Maybe a ground lift would have helped? It's something that happens quite often to me whenever I use a house system's feed.

Okay.. I thought you had already recorded what you could and were faced with "fixing it". If not, then my post was more or less irrelevant, sorry.

Still ...a pretty unique product, I recommend you investigate it as a backup plan in the future. Way!! more than a clicks and buzz fix. It can memorize a noise and remove it. (like a motorized camera running for example... which is what led me to it.)

No, you are correct in that for this event I have recorded the signal and the signal contained the radio traffic which will need a post-production fix. What is odd, is that the traffic did not appear until late in the production. I may be able to clip it out with the Floorfish (or the plugin you mentioned) since the radio signal is very weak.

I also have ambient audio recorded from my AT897 shotgun, and ambient audio from the second cam (just an on board mic on the GS320, so nothing of any note). So I have other audio sources, and considering the noise level on the sound board feed, it might be better to just use the ambient recording from the shotgun.

But should this situation arise again, I want to be more prepared with a solution that gets it right before writing to tape.

What is odd, is that the traffic did not appear until late in the production.

Since what you are picking up is an AM broadcast station, the late arrival of the traffic was likely due to sunset in the area that the signal originated from. AM stations have a problem in that their signals will travel great distances at sunset due to bouncing off the ionosphere. Therefore, they have three options... shut down at night, go to reduced power, or switch to a directional signal using a phased antenna array. All of this so that they don't interfere with other stations on the same frequency in other markets.

The basics for detecting, rectifying, and amplifying an AM radio signal exist in many electronics setups. The first time this happened to me was when I was in my early teens. It was around 2AM and I had been playing my electric guitar. It was very faint and I struggled to listen. It turned out to be a Canadian broadcast station. At first, I couldn't tell exactly where the sound in the room was coming from. Then I discovered sound was coming through my amp speakers. It scared the living crap out of me! I thought the 'other world' was trying to speak to me.

As was stated, balanced cabling to shield out unwanted signal will take care of this in most cases. In the example above, I had an unbalanced guitar cord, going to a distortion pedal, then on to the amp. Antenna, detector, and amplifier. Voila... you have an AM receiver.

-gb-

Reminds me of a time back in my TV news reporter days, I was doing a stand up, long mic cable on the street. When we got back in the edit booth the local beautiful music station (AM) gave me a nice sound bed. LOL. The station was a couple buildings away from me with the microwave to the transmitter on the roof. (shorter cable later and it wasn't an issue)

As was stated, balanced cabling to shield out unwanted signal will take care of this in most cases. -gb-


1) So will a 1/4" to XLR adapter and the use of my XLR cable get me to what I need to use the headphone jack (complete with its power problems but at least minus AM station pickup)?

2) To completely eliminate both problems (power buzz & hum and AM station) I understand I would need to know the sound board well enough to be able to pull an AUX out (at either line or mic) and then have an appropriate limiter to chop a line down to Mic for input to the Beachtek.

I would like to go with solution #2 because it eliminates the power buzz, but I doubt I'll be able to know my way around every house PA mixer and get permissions from the tech behind it to fiddle with their output plugs to get what I need.

1) So will a 1/4" to XLR adapter and the use of my XLR cable get me to what I need to use the headphone jack (complete with its power problems but at least minus AM station pickup)?No, I don't think so. As Seth pointed out earlier, you'd still be dealing with un unbalanced signal that is prone to picking up all sorts of noise, the more the longer the cable is that you use. If all you have is an unbalanced output (headphones, RCA, etc.), you can however run a SHORT cable to a balancing transformer, such as this one
http://www.rane.com/pdf/bb22dat.pdf
and run a balanced signal from there into your Beachtek, and that cable can be as long you need it to be. That would protect you much better from picking up noise.

2) To completely eliminate both problems (power buzz & hum and AM station) I understand I would need to know the sound board well enough to be able to pull an AUX out (at either line or mic) and then have an appropriate limiter to chop a line down to Mic for input to the Beachtek.

I would like to go with solution #2 because it eliminates the power buzz, but I doubt I'll be able to know my way around every house PA mixer and get permissions from the tech behind it to fiddle with their output plugs to get what I need.Well, keep trying. The basic ways to operate analog mixers are pretty similar between different makes and models of mixers. Typically, you have one AUX knob per input channel and per AUX output. The knob controls how much of that channel's signal is added to that AUX output. So as a starting point, plug your XLR cable into the mixer's AUX1 output, then adjust the kbobs labeled "AUX1" such that you open it a little bit for all channels you which to record, and close it completely for the other channels. That should give you something on your XLR cable. Then adjust the AUX levels from there.

It may take a little time to set it all up such that you get the right levels of everything, but the basic signal flow should be pretty straightforward that way. And you'd get a clean, balanced signal right out of the mixer. Just practise doing it, it'll be worth it!

- Martin

Since what you are picking up is an AM broadcast station, the late arrival of the traffic was likely due to sunset in the area that the signal originated from. AM stations have a problem in that their signals will travel great distances at sunset due to bouncing off the ionosphere. Therefore, they have three options... shut down at night, go to reduced power, or switch to a directional signal using a phased antenna array. All of this so that they don't interfere with other stations on the same frequency in other markets.

>>>>Well, sort of. When the FCC started laying things out for AM radio stations, there were at least three classifications based on power and coverage area. The clear channel stations (no connection to the company that eventually came to be called 'Clear Channel', were (are) 50 kW stations and mostly in big markets. They had the "right of way" , but even they go from omni to directional at night, mostly to not interfere with Canadian stations.

>>>>The less powerful AM stations have less right of way so they have to change pattern or go off the air. Some of these are directional during the day already, but change direction at local sundown and back at sunrise unless they have "presunrise or "post sunset" authorization. That authorization was given to some stations who pleaded that a 4:45 PM sign off in December (for example) would prevent them from even having a PM drive program (and the ad revenue it generated.)

As was stated, balanced cabling to shield out unwanted signal will take care of this in most cases. In the example above, I had an unbalanced guitar cord, going to a distortion pedal, then on to the amp. Antenna, detector, and amplifier. Voila... you have an AM receiver.

-gb-

This is true!

Regards,

Ty Ford

No, I don't think so. As Seth pointed out earlier, you'd still be dealing with un unbalanced signal that is prone to picking up all sorts of noise, the more the longer the cable is that you use. If all you have is an unbalanced output (headphones, RCA, etc.), you can however run a SHORT cable to a balancing transformer, such as this one
http://www.rane.com/pdf/bb22dat.pdf
and run a balanced signal from there into your Beachtek, and that cable can be as long you need it to be. That would protect you much better from picking up noise.

Ok, so the fact that an XLR cable is used doesn't mean the signal is balanced. I would need a device to specifically create the balanced signal and send it over the XLR cable to the camera. So running a 1/4" headphone -> 1/8" cable to RCA splitter (L & R dedicated RCA) into the device you mentioned -> 20'x2 XLR cables -> XLR to something to step it down to 1/8" stereo mini jack into cam or a mono 1/8" mini jack into Beachtec.

Well, keep trying. The basic ways to operate analog mixers are pretty similar between different makes and models of mixers. Typically, you have one AUX knob per input channel and per AUX output. The knob controls how much of that channel's signal is added to that AUX output. So as a starting point, plug your XLR cable into the mixer's AUX1 output, then adjust the kbobs labeled "AUX1" such that you open it a little bit for all channels you which to record, and close it completely for the other channels. That should give you something on your XLR cable. Then adjust the AUX levels from there.- Martin

about 1/2 thorough the event I found the Aux feed on the lapel input channel, but for some reason my AUX out via XLR direct to Beachtec (and monitored via headphones from the GL2 headphones out port) was not getting any audio. It is like there was some toggle on the mixing board that said "turn on this route" that I was missing because no amount of adjustments to the Mic1 Aux8 level could get the AUx8 line to register anything.

This leaves me wondering if I should be bringing my audio tech partner to all the events I shoot just so I don't need to mess with this in the future.

Since what you are picking up is an AM broadcast station, the late arrival of the traffic was likely due to sunset in the area that the signal originated from. AM stations have a problem in that their signals will travel great distances at sunset due to bouncing off the ionosphere. Therefore, they have three options... shut down at night, go to reduced power, or switch to a directional signal using a phased antenna array. All of this so that they don't interfere with other stations on the same frequency in other markets.
-gb-

Amazing. Now that I think back, it was right about sunset (started at 7pm went till 8:30ish). Huh. Basic HAM radio facts for the win.

This leaves me wondering if I should be bringing my audio tech partner to all the events I shoot just so I don't need to mess with this in the future.[/QUOTE]

Ah! There's a good idea!

Regards,

Ty (audio tech) Ford

Ok, so the fact that an XLR cable is used doesn't mean the signal is balanced. I would need a device to specifically create the balanced signal and send it over the XLR cable to the camera. So running a 1/4" headphone -> 1/8" cable to RCA splitter (L & R dedicated RCA) into the device you mentioned -> 20'x2 XLR cables -> XLR to something to step it down to 1/8" stereo mini jack into cam or a mono 1/8" mini jack into Beachtec.Yes, that should give you a balanced signal for the long portion of your cable run.

about 1/2 thorough the event I found the Aux feed on the lapel input channel, but for some reason my AUX out via XLR direct to Beachtec (and monitored via headphones from the GL2 headphones out port) was not getting any audio. It is like there was some toggle on the mixing board that said "turn on this route" that I was missing because no amount of adjustments to the Mic1 Aux8 level could get the AUx8 line to register anything.Another thing you can do is have XLR splitters available for each input channel, so that you can branch off all the relevant sources and feed them into your own mixer. Insert the splitter on the inputs into the house mixer. That should protect you from running into unexpected surprises with audio mixers that you don't fully understand.

This leaves me wondering if I should be bringing my audio tech partner to all the events I shoot just so I don't need to mess with this in the future.You have an audio tech partner? Of course you should bring him or her along, whenever that is feasible! Having a person dedicated to audio is a significant improvement over doing video and audio all at once.

- Martin

Yes, that should give you a balanced signal for the long portion of your cable run.
Great. I may have to try that. Another problem is I don't want to run a stereo signal because my on cam shotgun is using the left chan so I will need a mono signal from teh board. Considering that everything except CD music is mono, that wont' be a problem to just use one cable (also less expensive than buying another long XLR cable)

Another thing you can do is have XLR splitters available for each input channel,
Ahh. a very interesting idea. I would need to know if the incoming XLR signal from the UHF receiver was mic level or line level. I suppose a Mic level signal cannot be split (or may be I'm wrong there).

You have an audio tech partner? Of course you should bring him or her along, whenever that is feasible! Having a person dedicated to audio is a significant improvement over doing video and audio all at once.- Martin

Yes, but he is very expensive. I only use him for large events, or events with too tight of schedules for me to afford messing around with strange mixers. This event was very small, low margin, low profit. Given my need to pay December's mortgage, I'm trying to cut everything possible to keep treading water.

I suppose a Mic level signal cannot be split (or may be I'm wrong there).There are splitters for mic and for line level signals. With mic level, you just got to be careful with phantom power if the mixer provides that for the mic. Typically, there's an output labelled "direct" which should go the input of the device providing phantom power, and a second output that can go to another device.

- Martin

Everyone seems to be telling you what you did wrong and how to avoid it. No one is telling you how to fix it in post.

This is a common necessity in forensic work. You put a wire on someone to tape a clandestine meeting, and the meeting occurs in a very noisy bar, say, with a loud juke box. What you do is record another channel simultaneously, with just the juke box (maybe put a mike in front of the juke box. You might even wire another operative to tape this channel).


Now you have a recording of the audio you want, swamped by audio you don't want -- and a separate recording of the hated audio that did the swamping. There is software available to take the two files, subtract the unwanted-audio track from the desired audio track(s), and give you much cleaner audio. I could name one such program, but I don't want to get a rep for shilling someone's product excessively, even though I'm only their happy customer and haven't ever met them.

Swell, you say. I didn't do that. I don't have a tape of the radio station that I can have the software subtract. Ah, but maybe the radio station DOES have one. Or maybe you can record (in mono, I guess) the same "musical" selections the station played, and then at least get rid of the music, although you'd still have the DJ's voice in between selections (which might blend in with audience noise anyway).

The software versions that will do this forensic-type work for the cops will also do it for you. Unfortunately, it costs more than the non-forensic versions of the same software. How badly do you want to clean up your capture?

Carl,

Have you actually done this yourself?

Regards,

Ty Ford

The software versions that will do this forensic-type work for the cops will also do it for you. Unfortunately, it costs more than the non-forensic versions of the same software. How badly do you want to clean up your capture?

Not enough to bother paying for yet another software package. I have Soundforge & Vegas8pro. I've already cut it together and I will end up using the over the air shotgun audio or audio combined from the second cam (just an onboard cam).

This is a $300 gig, so nothing fancy.

I mainly wanted to know how to avoid this in the future with a hardware solution so I don't have to touch anything in post.

Though I would love to play with forensic level software!

The clear channel stations (no connection to the company that eventually came to be called 'Clear Channel', were (are) 50 kW stations and mostly in big markets. They had the "right of way" , but even they go from omni to directional at night, mostly to not interfere with Canadian stations.

Your last sentence sort of bears out what i said. Directional, low power, or off air. For some stations, it's a combination of the first two.

I'm familiar with the 'clear channel' AM 50KW stations. I've got a bit of radio broadcast pedigree in my background. DJ, First Class license, ASET degree, yada, yada, yada.

-gb-

Carl,

Have you actually done this yourself?

Regards,

Ty Ford


Nope. I've read about it, and my cop friends (I have a lot of cop friends) assure me that (1) it's a standard approach for a well-equipped lab on big cases that warrant the investment of time, (2) they've heard and used the output, and (3) they were blown away. As an electrical engineer I know that the theory is sound.

I don't own the (forensic) versiion of Diamond Cut that includes this capability, though, and have never done it myself.

\I've got a bit of radio broadcast pedigree in my background. DJ, First Class license, ASET degree, yada, yada, yada.
-gb-

right. me too. 1st phone commuted to a general, couple of CE gigs at stations.

Ty

Nope. I've read about it, and my cop friends (I have a lot of cop friends) assure me that (1) it's a standard approach for a well-equipped lab on big cases that warrant the investment of time, (2) they've heard and used the output, and (3) they were blown away. As an electrical engineer I know that the theory is sound.

I don't own the (forensic) versiion of Diamond Cut that includes this capability, though, and have never done it myself.

Well sure the theory is sound, but theory and practice seldom agree. In this case,
{You said: You put a wire on someone to tape a clandestine meeting, and the meeting occurs in a very noisy bar, say, with a loud juke box. What you do is record another channel simultaneously, with just the juke box (maybe put a mike in front of the juke box. You might even wire another operative to tape this channel).}

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

That's different from trying to reclaim audio with any fidelity.
Regards,
Ty

Right, which is why I am much more interested in correcting the problem at the source and getting a hardware solution. As much as I like my work, I hate the wasted time in Post to fix these annoying but devastating errors.

Jason,

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.

That either meant maybe they weren't hearing it during record and it was there, or somehow it got in later. Like maybe during transfer.

Balanced audio is the best defense against RF. IIR, you have unbalanced audio inputs and a collection of unbalanced adapters to get to the camera. That in itself could do it. Although sometimes, it still gets into balanced audio as well.

You're best defense is having a variety of solid front end gear and a stash of different gozinta and gozouta cables. 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.

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. 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.

Regards,

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.

and a stash of different gozinta and gozouta cables.

Is that a brand name? ;-)

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.

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).

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).

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 (http://www.neutrik.com/us/en/audio/204_1603252336/EMC-XLR_Series_productlist.aspx)
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

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.

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

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.

....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>

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