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Filed under: Audio •

I Can’t Hear You: Correct Audio Connections

I felt compelled to write on this subject because of a real-life experience that happened years ago. Trish and I were scheduled to show tapes and speak about our work at an event. We had both BetaSP and VHS tapes, as well as some QuickTime movies to show from a Mac. As is our custom, we asked to inspect the gear before we were scheduled to go on, just to make sure everything would go smoothly.

I started at the BetaSP deck. There was nothing connected to its normal audio output connectors - a problem, since we really focus on the interplay between audio and visuals in our work. However, there was something plugged into the “monitor” output on the back of deck. This is an extra RCA-style output jack meant to be connected to the corresponding input on some video monitors (to hear your work through that great two-inch speaker so generously built in). They were using this, but not with a phono plug inserted - instead, they managed to jam into a Walkman-style headphone plug into it, which then went to a pair of RCA connectors. An inauspicious start.

This went not to an audio mixer or amplifier, but to the audio inputs on the back of the VHS deck. Well, okay; when nothing is playing, many decks pass the audio and video from their input straight to their outputs - kind of handy, actually. However, there was nothing plugged into the audio outputs from the VHS deck - puzzling. I moved around to the front of the deck, and audio was being taken from its headphone output jack instead (through a couple of adapters, by the way).

This didn’t got to a mixer or amplifier, but instead to some inexpensive computer speakers on the desk we were supposed to speak from. Finally, audio was taken from the headphone jack on the front of one of these speakers, and routed to the amplifier that powered the main speakers in the room.

It worked - more or less. One channel of the BetaSP didn’t really come through, and overall, it sounded lousy. So why did they wire it this way? Not because they were stupid or because they were out to get us; they wired it that way because they didn’t know any better, and audio wiring isn’t discussed in most desktop video manuals and books for them to learn from.

If you (however sheepishly) find yourself in a similar boat, read on - and we’ll untangle some of the mysterious mess of audio cabling.

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is there a way to tell what level each device is? ie: +4, -50 etc. or just have to find by looking thru manuals. for instance, what is a macpro?

Posted by .(JavaScript must be enabled to view this email address)  on  03/16  at  05:55 PM

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The connectors provide a clue.

If it’s an 1/8” mini plug, or an RCA (phone) jack, it’s -10 dB, which is the “consumer” level - which pretty much all computer (MacPro included) are. If it’s an XLR (the big metal barrel with 3 pins inside), it’s either +4 dB (pro level), or if it’s connected to a microphone, then it’s roughly -50dB (mic level).

The wild card are 1/4” plugs and jacks. If plugged into a guitar, it’s closer to mic level; if it’s plugged into gear, it could be either -10 or +4 dB. A clue is provided by whether it’s tip-sleeve (a mono connector), which means it’s probably unbalanced, and therefore line or consumer level (-10 dB) or if its tip-ring-sleeve (a stereo connector), which means it’s probably balanced and therefore pro level (+4 dB).

That’s the clues. To be sure, look for legending or switches on the back of gear, or worst case, the manual (thankfully, many manuals can be found online these days…).

good luck -
Chris

Posted by Chris Meyer  on  03/17  at  12:36 PM

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thanks chris, big help. i think i may add the mackie to the mix just to have it handy when i need it. i mainly only monitor audio with fcp and AE while working, so i want to make sure i get it all in order.

Posted by .(JavaScript must be enabled to view this email address)  on  03/17  at  12:41 PM

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As noted at the end, the Mackie is my “I’m heading into the wilds and I need to be absolutely sure it works, and works well” mixer. If I’m going to be in a more controlled environment (i.e. nobody’s going to drop it), I have time to make sure I understand the signal levels, and I’m trying to save some bucks, then the Behringers will do. I had a Behringer in the tape deck rack in our studio for years, but I’m bringing the Mackie to NAB for my audio session…

- Chris

Posted by Chris Meyer  on  03/18  at  11:57 PM

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By the way - if you are connecting your MacPro to a mixer and/or other gear, I would get a Radio Shack Ground Loop Isolater for the connection. (See http://provideocoalition.com/index.php/cmg_blogs/story/buzz/)

good luck -
Chris

Posted by Chris Meyer  on  03/19  at  12:01 AM

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May I also recommend at least two of Sure’s in-line XLR variable attenuators. I know of no simpler way to handle the myriad of different line levels, and line to mic levels than these buggers. They’re cheap, small, durable, and- variable.

Lastly, as ubiquitous as iPods are, an adaptor that goes from 1/8” stereo to RCA + RCA to 1/4” adaptors and RCA to XLR adaptors allows me to put my audio into any source deck and make sure the path after the deck is working- without playing my actual program material.

This is a great way to slowly ease up the audio on the iPod and not be startled by some super loud volume the previous user left because their program audio was so low.

Posted by Anthony  on  03/20  at  04:49 PM

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Good suggestions, Anthony. And as long as you are filling your survival kit, Shure also makes a transformer with an XLR on one end (for a mic) and a 1/4” tip-sleeve phone plug on the other for plugging mics into line level inputs.

BTW, those 1/8” stereo to dual RCA adaptors are the quickest to die; keep extras around.

- Chris

Posted by Chris Meyer  on  03/25  at  12:12 AM

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