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Old May 18th, 2011, 04:51 PM   #1
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Recording from telephone

I've just been asked to look into recording audio commentary via telephone line. The idea is this...Recording audio commentary for the extras in a feature DVD. Several people will be gathered to watch the movie and deliver commentary. In room commentary will all be recorded with a pair of AT-2020 mics and an omni-directional mic. I have four mic inputs, BTW! Fourth input, we would like to be taken from a phone line. I've never recorded off a phone line before, so any input would be great.

What I really need is a way to get a signal from a phone line into an M-Audio Delta 44 sound card. I'll be running a Mackie 1202 VLZ mixer for the room mics, into the Delta 44. So I'm assuming I would be able to use some device to go between the phone line and the input on the Mackie in order to get it into the DAW. I could be wrong....
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Old May 18th, 2011, 05:01 PM   #2
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Re: Recording from telephone

There may be a cheaper, more ad-hoc way, but the pro way is to use a phone hybrid (see sample here, not necessarily a recommendation: JK Audio JK Audio Auto Hybrid Telephone Audio Interface Phone Interface & Dist. at Markertek.com

Note there are sometimes strict laws about recording a phone conversation, I have had it recommended to me to record the persons on the other end giving their acknowledgement that they are being recorded and their consent...just btw.
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Old May 18th, 2011, 05:11 PM   #3
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Re: Recording from telephone

Thanks Battle! I was looking at some JK Audio products along this line. As for permission, I would fly like I always do when interviewing, either on camera or only on mic, always record a statement of their name and permission to use the recording!
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Old May 18th, 2011, 05:33 PM   #4
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Re: Recording from telephone

On the low end, I think this guy might work...
Rolls Corporation Rolls PI9 Phone Patch Telephone Audio Interface Phone Interface & Dist. at Markertek.com

Anything I get for this will be tested before actual use, of course.
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Old May 18th, 2011, 06:33 PM   #5
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Re: Recording from telephone

Of course you realize the audio quality will be terrible: 300 - 3,000 Hz bandwidth, fair amount of noise, probably a lot of distortion (mostly caused by the mic at the sending end).

The first thing you need to determine is whether your phone connects directly to the POTS line (Plain Old Telephone Service), or whether it is some sort of digital phone, possibly connected through a digital PBX.

If it's an old style analog phone connected to the POTS line, things are more predictable. POTS lines are powered by a nominal 48vdc battery at the central office, so the first thing you must do is isolate the phone from your recording equipment, by using an audio transformer capable of line-level isolation. You do NOT want to dump that 48 volt battery into your mixer input! First choice is to connect the primary in parallel with the two leads going to the earphone in your telephone. Second choice is to connect the primary directly across the POTS line itself, but in that case you will need a series capacitor to keep the DC from saturating the transformer primary. The audio output will probably be some intermediate level between typical mic and line level, so be prepared with pads if needed.

Phone lines run for miles with no shielding (although they are twisted and theoretically balanced pairs) so they typically have a lot of hum. You can remove that later in post, since the transmitted audio won't have much content below 300 Hz.

If you're coming off a phone that goes through a digital PBX, then anything is possible. Four-wire cabling is typical, one pair for DC and one pair for "other." Other may be digitized voice, or signalling, or whatever... different PBX systems use different protocols. So the only safe bet is to open up the handset and connect your iso transformer primary across the earphone terminals. You may have a bit less hum (compared to a POTS setup) if the PBX does any bandpass filtering. OTOH, you may have various amounts of digital noise mixed in with the desired audio... again, if you're lucky, you can remove this in post with a LPF, since the actual telephone audio pretty much ends at 3,000 or 3,500 Hz.

In any case, remember to remove the mic element from the telephone handset, or else that will pick up room noise which will bleed into the audio you're recording. Telephones are, in theory, duplex, but in fact use the same pair of wires for audio going both directions, so there is always some bleed (called "side tone" in the TELCO industry).

Remember, too, that the earphone (where you're connecting your iso transformer) is more or less a dynamic mic, so it will pick up loud noise in the room! And since it has a big coil of wire, it is also susceptible to nearby magnetic fields. If you hear a lot of hum in your audio, be sure the telephone handset isn't sitting near a power transformer, fluorescent light, etc.

Or, yeah, you can spend some money and buy or rent some sort of commercial phone coupler. Even so, the audio will still sound like a phone call.
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Old May 18th, 2011, 06:41 PM   #6
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Re: Recording from telephone

I wound up "solving" this problem in a very low-tech way. After trying a lot of different options, I found the easiest and best way was to put a lav between my ear and the earpiece of the phone. Doesn't seem like it would well, but for me it did for me.

Good luck.
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Old May 18th, 2011, 07:27 PM   #7
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Re: Recording from telephone

Quote:
Originally Posted by Andy Balla View Post
I've just been asked to look into recording audio commentary via telephone line. The idea is this...Recording audio commentary for the extras in a feature DVD. Several people will be gathered to watch the movie and deliver commentary. In room commentary will all be recorded with a pair of AT-2020 mics and an omni-directional mic. I have four mic inputs, BTW! Fourth input, we would like to be taken from a phone line. I've never recorded off a phone line before, so any input would be great.

What I really need is a way to get a signal from a phone line into an M-Audio Delta 44 sound card. I'll be running a Mackie 1202 VLZ mixer for the room mics, into the Delta 44. So I'm assuming I would be able to use some device to go between the phone line and the input on the Mackie in order to get it into the DAW. I could be wrong....
I don't think your primary problem is going to be the telephone audio.

Unless I misunderstand your room recording approach, I'd expect you to get VERY iffy primary recordings of the room participants. Micing a ROOM is almost always a bad idea when you want crisp, intelligible spoken word recordings. You need to mic the individual PEOPLE.

This is particularly true when there's a chance that people will speak over each other but even if they don't you're facing multiple reflections, various distances from the different people to the mics, and the way the room enhances, splashes, or muffles any or some of the parts of the audio spectrum for the sounds making their way from mouths to mic.

If you have 5 primary people in the room, you won't get best results unless you have 5 mics - one on each person - micd as closely as possible. If you do get them all miced properly, then the next battle is whether you feed them to iso recording channels (a very good idea) or run the mics to a mixer an capture only the mixed signal.

Bottom line. Multiple voice recording "in situ" is almost always more a challenge than it seems.

Good luck.
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Old May 18th, 2011, 08:17 PM   #8
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Re: Recording from telephone

Another rather common approach is to conduct the interview (or coordinate the comments) over the phone, but have a LOCAL, higher-quality recording scheme at the far end. The big-budget operations just hire a local (at the far end) audio production guy to go out with his regular kit (high quality mic, mixer, recorder, monitoring, etc.) to record while the subject talks on the phone to the interviewer. But the subject's voice is captured by the high-quality kit and then the good recording is sent back to the producer, either online, or via snail-mail.

You could even do a low-budget version of this by using Skype to conduct the phone conversation, and either use the built-in Skype recording function, or a 3rd party recording software (like Total Recorder). Even a $5 "computer mic" is typically higher quality than using the PSTN (public switched telephone network) with a cell phone or a land-line hard-wired phone.

And Skype would also allow viewing in both directions.
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Old May 18th, 2011, 09:24 PM   #9
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Re: Recording from telephone

If you don't mind that it sounds like they're on a phone, I've found the $56 JK Audio QuickTap to work rather well for recording.
JK Audio QWK-TAP QuickTap Telephone Handset Tap Phone Interface & Dist. at Markertek.com
Here's a video I put together to help a customer with their Edirol R-09 and QuickTap - jump to about 2:36 to see how it hooks up.
YouTube - Edirol R-09 with QuickTap for Phone Recording
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Old May 18th, 2011, 09:51 PM   #10
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Re: Recording from telephone

Thanks for all of the responses. Here is the setup... We will record 4-5 people in the room at one time. Separately, we will record phone comments from out of state actors who worked on this film. @ Bill, I'm not worried about getting good sound of the primary group in the room. I'm used to this kind of thing and have no problems there. The phone recording is the unknown for me.

I'm looking at the JK Audio QuickTap, as well as the Rolls PI9, on the low end, and also the JK Audio THAT 2 and their Inline Patch Telephone Hybrid on the higher end. My main goal is that the phone audio sounds usable...
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Old May 18th, 2011, 11:16 PM   #11
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Re: Recording from telephone

As long as "usable" means it does sound like it was recorded over a telephone, you should be OK. Couplers aren't magic. And you can clean up residual hum with software. But of course there's nothing you can do to make it sound as if it was recorded with even a $20 microphone and a clean recorder. A lot depends on the mic in the telephone that the actor is using. If it's an old-style carbon mic, the audio will sound raspy and pretty nasty. If it's a newer electret module, the audio has a chance of sounding like a clean phone call. That's as good as it will be. Can you live with 300 - 3,000 Hz bandpass with sharp cutoffs?
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Old May 19th, 2011, 08:32 AM   #12
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Re: Recording from telephone

The other factor I was going to mention, but it doesn't seem like it will be an issue after reading all the posts, is if you needed for the group of people in the room to also hear and speak with the phone interviewee. That would add a huge layer of complications!

For simple phone recordings, I use an Excalibur HC-1 Handi-Coupler (don't know if it's even still available) as well as an Ebtech Hum Eliminator to isolate from the phone system.

For larger setups I use the JK Audio Remote Mix-3 and the Ebtech.

For interactive phone/audience setups I use a Telos One hybrid.
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Old May 19th, 2011, 09:59 AM   #13
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Re: Recording from telephone

I've done a few interactive phone/audience setups using a Gentner system, (don't recall the model #) but it involved questions from the audience. We had stand-mics for that, but there was always some yo-yo who would blurt out a question in the direction of the nearest PA speaker. Like the person was hiding in there. Quite funny actually.

That said, if you have any 'say', suggest that the 'talent' on the phones use good quality hard-wired phones. Avoid home wireless and cell phones if possible... and of course speaker phones.
(My 2 cents)
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Old May 19th, 2011, 10:27 AM   #14
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Re: Recording from telephone

I keep a Gentner Hybrid Coupler in my bag for such situations.
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Old May 19th, 2011, 11:41 AM   #15
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Re: Recording from telephone

No question about it, Gentner is the best. Their hybrids, if carefully balanced, allow good 2-way duplex connectivity. They're not cheap and, based on the initial description, full duplex is probably not needed for this situation. But they definitely have a long and good reputation.
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