DV Cam Interfaces

Handy DV Cam Interfaces

by Matt Hamilton
A number of our customers call us with questions about recording sound to the audio tracks on the Canon XL-1, GL-1, Sony VX1000, VX2000, PD150’s or some other prosumer camcorder. Usually, they are working on a documentary or independent film. However, these cameras are becoming much more prevalent on ENG crews and in other professional applications.

Although they were designed for consumers, their attractive pricing, coupled with 16-bit/48kHz DAT quality recording capabilities, has lead to their gradual acceptance in certain areas of film and video production. While their preamps are not going to be on par with a Cooper mixer, they do yield decent results for dialog recording. The stereo mic on the Canon XL-1, for instance, yields surprisingly clean recordings for stereo ambience and room tone. And what better way to gather “behind the scenes” footage than to send out a “disposable” camera?

In a recent posting to an audio newsgroup it was rumored that NBC is now using Sony PD150 camcorders for B-roll news footage. In this scenario, the camera operator becomes the sound person as well. It makes me wonder if I shouldn’t learn to be a camera operator to stay competitive! With that in mind, can an audio person afford not to be prepared for a camcorder shoot?

Not the Ideal

Unfortunately, there are a few well-known problems with interfacing your pro mixer and any consumer device, let alone a camcorder.

There are delicate stereo mini-jacks that can snap solder joints inside the camera’s housing if they are jerked around too much. Of course, we all know how calm everything is on any set. (Insert sarcasm here).

Proprietary electret voltages, impedance mismatches, and ground loops can lead to various audio artifacts. Since very few camcorders provide phantom power, your mic selection is severely limited.

None of these cameras allow confidence monitoring of the audio being recorded, despite very low headroom on the mic pre’s, which can distort easily. And, you can forget having access to a level meter, which is buried somewhere deep within the menu structure or only visible through the camera’s eyepiece.

So, how do you deal with these problems?

Bottom Feeders

While interface boxes for these cameras are nothing new, there were a few aspects that sometimes rendered them more of a hindrance than a help. Since they were mounted on the bottom of the camera, the level pots were on the side within easy reach of the camera operator’s hand. This lead to the inevitable accidental level changes. The XLR's entered the opposite side of the box making it awkward to handle. The metal construction of these boxes added weight to the camera. With the cables and extra weight, it made it difficult to control camera movements as the balance of the camera was thrown off. The camera operator could find the camera suddenly jerked from his hands during those unexpected movements that occur while running and gunning. SteadyCam shots were rendered impossible or at best very tricky as the tugging of the cables interfered with the float of the camera.

While you may be expecting a list of adapters and tricks to overcome the previously mentioned problems, they have all been addressed with the XLR-BP Professional from Studio 1 Productions.

Getting It Under Your Belt

The first major improvement is indicated by the initials BP in the name. The XLR-BP Pro clips to the camera operator’s belt with audio being carried to the camera through a 4 foot shielded cable. In acknowledgement of the rigors of the field, the belt clip is replaceable. In one fell swoop this removes nearly every problem that could arise with other camera-mounted systems. The weight has been transferred to the belt and any sudden cable jerks are effectively strain-relieved and isolated from the camera. Of course, the camera person may lose their pants.

What about the added weight? This update has been constructed of lightweight, high impact ABS plastic. Speaking on the phone with the designer of the XLR-BP Pro, he confessed to beating the prototype boxes with a hammer to test their ruggedness. Talk about field testing! It might just survive a few ENG shoots after all.

The controls are arranged intelligently for belt mounting as well. The “non-belt” side of the box has two balanced XLR inputs. All the controls are mounted on the front side of the box. When the XLR-BP Pro is mounted on your left side, all the controls face forward, and can be easily located by touch. Going from top to bottom you have:

1. audio input 1 level control
2. audio input 2 level control
3. an 1/8” aux input jack for wireless mics
4. a Ľ” aux input jack
5. the mic/line switch for input 1
6. the mic/line switch for input 2
7. the mono/stereo switch, and
8. the ground switch for isolating hums and grounding problems.

To assure the best audio quality possible, audio signal enters an impedance matching transformer in a heavily shielded housing. This transformer is an improvement over the previous transformer, according to Studio 1, yielding a better frequency response from 20Hz-20kHz.

If you still aren’t sold on the belt pack design, here is one more thing to consider. More and more camera manufacturers are putting the eject button on the bottom of their camcorders. This is true for the JVC VS200, DV2000, TRV340, and Canon ZR4045 to name a few. With a camera mounted interface box, you wouldn’t be able to eject your tape without first removing the box. As the saying goes, “The devil is in the details”. It is this awareness of the DV cam market that makes the XLR-BP Pro extra nice. List price: $189.

Setting Levels with the Mixer

Probably the trickiest thing in any audio setup is a proper gain structure. It is especially difficult when you are interfacing with a camcorder. The most important point to remember in this situation is that you will hear distortion before the meters actually show any overs. The incredibly small headroom these preamps have make it especially important to keep an eye on levels during recording. If you have a mixer, send a tone at the unity gain position. If you have VU meters, this will be the 0 VU setting. Some peak meters also have a 0 point for the unity gain position. Often, the master level control will have a détente at this position.

While still sending tone, set the audio level controls on the camera to register the tone at the –20 mark. This will appear too low. It is not. You must set it this low to prevent crapping out the preamps when you have those sudden peaks. If you are filming a documentary with high sound levels, you’ll need to set it even lower. Let your ears be the judge, though. Listen to what is coming through the headphones on the camera to make certain it sounds okay, even if the levels look good.

Most audio recorders offer confidence monitoring so you can hear if anything is actually being recorded. Every camcorder I know of does not offer this option. What you are hearing is actually the audio coming into the camera and being routed straight to the headphone jack. In order to hear what was actually recorded, you must stop the camera, rewind, and listen back. I would recommend you do this at the beginning of the shoot to make sure you aren’t getting any distortion to tape. As I said before, don’t trust the meters. Trust your ears.

I’d also recommend a Remote Audio Breakaway Betacam Cable (List Price: $235). I am assuming that you are either using the Studio 1 box or have XLR inputs on your camera. This cable allows you to send two audio channels to the camera and receive a monitor return signal from the headphone jack. It is wrapped into one nice, neat cable with a quick disconnect connector on the camera end. This allows the camera person to separate his tie to the audio person for quick breakdown and setup via one connector rather than unplugging 2 XLR’s and a mini-jack.

Setting Levels with Just a Microphone

If you aren’t using a mixer, you will have much less control over the audio. Once the level is set, you can’t adjust it on the fly while shooting. However, there are a few gadgets that can be of assistance. The Shure A15TG (List Price: $91.23) is a small, battery-powered 700 Hz tone generator. You can plug it into the mic cable and set your level to –20 on the camera as a preliminary setting. You will still need to monitor the audio signal, though.

There are two headphone amplifiers that you can get for this purpose. Both units run on a single 9V battery, and offer a volume control for your headphones. They are also much louder than the anemic headphone jacks on most camcorders. Even wide open, the camcorder headphone amps leave something to be desired.

The JK Audio Remote Amp (List Price: $215) accepts an XLR input and offers either an 1/8” or Ľ” headphone jack with volume control. To use this with a camcorder, you would need an 1/8” stereo connector to male XLR adapter cable coming from the headphone jack on the camera. Just feed that down an XLR cable of an appropriate length for your application. The other end of the XLR cable feeds into the Remote Amp mounted on your belt. A similar item would be the Rolls PM50sOB (List Price: $90). It has a Ľ” input, so you would need an 1/8” stereo to Ľ” stereo cable. We carry a full line of these cables at Trew Audio and are able to fabricate cables to order.

The Twist

On a final note, you may be reading this article saying, “Yeah, but prosumer camcorder recording is for the little man, I’m a macho sound engineer not to be troubled by such trivia”. Far be it from me to challenge your manliness, but I will add that the Studio 1 box works well as a transcription interface. You can feed timecode from the camera at line level into channel 1 with a BNC to male XLR adapter, and audio at line level into channel 2. Since it is a passive device, it will pass the signal when the pots are wide open and attenuate the signal as you turn down the level. By dropping the level on channel 1 you can effectively attenuate the timecode input to a decent level to prevent crosstalk on the cassette. In stereo mode the audio will be sent to separate tracks at mic level on the 1/8” right angle output jack. Just feed this into your transcription cassette or mini-disc. Voila! Transcription magic.

Conclusion

The Studio 1 Productions XLR-BP Pro offers unique features that make it well-suited to camcorder audio capture. As a balanced to unbalanced impedance transformer, there are other uses yet to be discovered. Overall, I’d say it’s good addition to your audio arsenal. Of course, you could also show up at family reunions in full audio gear and boom mic the entire event, ending all discussion once and for all about what it is you do for a living.

Editor's Note: (thanks to RAMPS for the NBC info and Glen Piegari for the transcription idea and details of the setup)


Handy DV Cam Interfaces
by Matt Hamilton A number of our customers call us with questions about recording sound to the audio tracks on the Canon XL-1, GL-1, Sony VX1000, VX2000, PD150’s or some other prosumer camcorder. Usually, they are working on a documentary or independent film. However, these cameras are becoming much more prevalent on ENG crews and in other professional applications. Although they were designed for consumers, their attractive pricing, coupled with 16-bit/48kHz DAT quality recording capabilities, has lead to their gradual acceptance in certain areas of film and video production. While their preamps are not going to be on par with a Cooper mixer, they do yield decent results for dialog recording. The stereo mic on the Canon XL-1, for instance, yields surprisingly clean recordings for stereo ambience and room tone. And what better way to gather “behind the scenes” footage than to send out a “disposable” camera? In a recent posting to an audio newsgroup it was rumored that NBC is now using Sony PD150 camcorders for B-roll news footage. In this scenario, the camera operator becomes the sound person as well. It makes me wonder if I shouldn’t learn to be a camera operator to stay competitive! With that in mind, can an audio person afford not to be prepared for a camcorder shoot? Not the Ideal Unfortunately, there are a few well-known problems with interfacing your pro mixer and any consumer device, let alone a camcorder. There are delicate stereo mini-jacks that can snap solder joints inside the camera’s housing if they are jerked around too much. Of course, we all know how calm everything is on any set. (Insert sarcasm here). Proprietary electret voltages, impedance mismatches, and ground loops can lead to various audio artifacts. Since very few camcorders provide phantom power, your mic selection is severely limited. None of these cameras allow confidence monitoring of the audio being recorded, despite very low headroom on the mic pre’s, which can distort easily. And, you can forget having access to a level meter, which is buried somewhere deep within the menu structure or only visible through the camera’s eyepiece. So, how do you deal with these problems? Bottom Feeders While interface boxes for these cameras are nothing new, there were a few aspects that sometimes rendered them more of a hindrance than a help. Since they were mounted on the bottom of the camera, the level pots were on the side within easy reach of the camera operator’s hand. This lead to the inevitable accidental level changes. The XLR's entered the opposite side of the box making it awkward to handle. The metal construction of these boxes added weight to the camera. With the cables and extra weight, it made it difficult to control camera movements as the balance of the camera was thrown off. The camera operator could find the camera suddenly jerked from his hands during those unexpected movements that occur while running and gunning. SteadyCam shots were rendered impossible or at best very tricky as the tugging of the cables interfered with the float of the camera. While you may be expecting a list of adapters and tricks to overcome the previously mentioned problems, they have all been addressed with the XLR-BP Professional from Studio 1 Productions. Getting It Under Your Belt The first major improvement is indicated by the initials BP in the name. The XLR-BP Pro clips to the camera operator’s belt with audio being carried to the camera through a 4 foot shielded cable. In acknowledgement of the rigors of the field, the belt clip is replaceable. In one fell swoop this removes nearly every problem that could arise with other camera-mounted systems. The weight has been transferred to the belt and any sudden cable jerks are effectively strain-relieved and isolated from the camera. Of course, the camera person may lose their pants. What about the added weight? This update has been constructed of lightweight, high impact ABS plastic. Speaking on the phone with the designer of the XLR-BP Pro, he confessed to beating the prototype boxes with a hammer to test their ruggedness. Talk about field testing! It might just survive a few ENG shoots after all. The controls are arranged intelligently for belt mounting as well. The “non-belt” side of the box has two balanced XLR inputs. All the controls are mounted on the front side of the box. When the XLR-BP Pro is mounted on your left side, all the controls face forward, and can be easily located by touch. Going from top to bottom you have: 1. audio input 1 level control 2. audio input 2 level control 3. an 1/8” aux input jack for wireless mics 4. a Ľ” aux input jack 5. the mic/line switch for input 1 6. the mic/line switch for input 2 7. the mono/stereo switch, and 8. the ground switch for isolating hums and grounding problems. To assure the best audio quality possible, audio signal enters an impedance matching transformer in a heavily shielded housing. This transformer is an improvement over the previous transformer, according to Studio 1, yielding a better frequency response from 20Hz-20kHz. If you still aren’t sold on the belt pack design, here is one more thing to consider. More and more camera manufacturers are putting the eject button on the bottom of their camcorders. This is true for the JVC VS200, DV2000, TRV340, and Canon ZR4045 to name a few. With a camera mounted interface box, you wouldn’t be able to eject your tape without first removing the box. As the saying goes, “The devil is in the details”. It is this awareness of the DV cam market that makes the XLR-BP Pro extra nice. List price: $189. Setting Levels with the Mixer Probably the trickiest thing in any audio setup is a proper gain structure. It is especially difficult when you are interfacing with a camcorder. The most important point to remember in this situation is that you will hear distortion before the meters actually show any overs. The incredibly small headroom these preamps have make it especially important to keep an eye on levels during recording. If you have a mixer, send a tone at the unity gain position. If you have VU meters, this will be the 0 VU setting. Some peak meters also have a 0 point for the unity gain position. Often, the master level control will have a détente at this position. While still sending tone, set the audio level controls on the camera to register the tone at the –20 mark. This will appear too low. It is not. You must set it this low to prevent crapping out the preamps when you have those sudden peaks. If you are filming a documentary with high sound levels, you’ll need to set it even lower. Let your ears be the judge, though. Listen to what is coming through the headphones on the camera to make certain it sounds okay, even if the levels look good. Most audio recorders offer confidence monitoring so you can hear if anything is actually being recorded. Every camcorder I know of does not offer this option. What you are hearing is actually the audio coming into the camera and being routed straight to the headphone jack. In order to hear what was actually recorded, you must stop the camera, rewind, and listen back. I would recommend you do this at the beginning of the shoot to make sure you aren’t getting any distortion to tape. As I said before, don’t trust the meters. Trust your ears. I’d also recommend a Remote Audio Breakaway Betacam Cable (List Price: $235). I am assuming that you are either using the Studio 1 box or have XLR inputs on your camera. This cable allows you to send two audio channels to the camera and receive a monitor return signal from the headphone jack. It is wrapped into one nice, neat cable with a quick disconnect connector on the camera end. This allows the camera person to separate his tie to the audio person for quick breakdown and setup via one connector rather than unplugging 2 XLR’s and a mini-jack. Setting Levels with Just a Microphone If you aren’t using a mixer, you will have much less control over the audio. Once the level is set, you can’t adjust it on the fly while shooting. However, there are a few gadgets that can be of assistance. The Shure A15TG (List Price: $91.23) is a small, battery-powered 700 Hz tone generator. You can plug it into the mic cable and set your level to –20 on the camera as a preliminary setting. You will still need to monitor the audio signal, though. There are two headphone amplifiers that you can get for this purpose. Both units run on a single 9V battery, and offer a volume control for your headphones. They are also much louder than the anemic headphone jacks on most camcorders. Even wide open, the camcorder headphone amps leave something to be desired. The JK Audio Remote Amp (List Price: $215) accepts an XLR input and offers either an 1/8” or Ľ” headphone jack with volume control. To use this with a camcorder, you would need an 1/8” stereo connector to male XLR adapter cable coming from the headphone jack on the camera. Just feed that down an XLR cable of an appropriate length for your application. The other end of the XLR cable feeds into the Remote Amp mounted on your belt. A similar item would be the Rolls PM50sOB (List Price: $90). It has a Ľ” input, so you would need an 1/8” stereo to Ľ” stereo cable. We carry a full line of these cables at Trew Audio and are able to fabricate cables to order. The Twist On a final note, you may be reading this article saying, “Yeah, but prosumer camcorder recording is for the little man, I’m a macho sound engineer not to be troubled by such trivia”. Far be it from me to challenge your manliness, but I will add that the Studio 1 box works well as a transcription interface. You can feed timecode from the camera at line level into channel 1 with a BNC to male XLR adapter, and audio at line level into channel 2. Since it is a passive device, it will pass the signal when the pots are wide open and attenuate the signal as you turn down the level. By dropping the level on channel 1 you can effectively attenuate the timecode input to a decent level to prevent crosstalk on the cassette. In stereo mode the audio will be sent to separate tracks at mic level on the 1/8” right angle output jack. Just feed this into your transcription cassette or mini-disc. Voila! Transcription magic. Conclusion The Studio 1 Productions XLR-BP Pro offers unique features that make it well-suited to camcorder audio capture. As a balanced to unbalanced impedance transformer, there are other uses yet to be discovered. Overall, I’d say it’s good addition to your audio arsenal. Of course, you could also show up at family reunions in full audio gear and boom mic the entire event, ending all discussion once and for all about what it is you do for a living. Editor's Note: (thanks to RAMPS for the NBC info and Glen Piegari for the transcription idea and details of the setup)