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Old September 6th, 2016, 05:26 PM   #1
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Unity gain

I have a Shure SCM268 four channel mixer and a Panasonic AG-AC130a. I'm having trouble doing unity gain. Does anyone have the same combination that could explain the steps? Thank you.
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Old September 6th, 2016, 08:01 PM   #2
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Re: Unity gain

I don't have ether device but my first guess is your pushing line level from the mixer into mic level on the camera.

Are you sure they are set to a matched signal? The mixer is selectable on the back of it. The camera may or may not be, I don't have one.

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Old September 6th, 2016, 08:02 PM   #3
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Re: Unity gain

Can you explain what you mean by "doing unity gain"?

Perhaps a description of what you are trying to accomplish would be helpful.
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Old September 6th, 2016, 11:09 PM   #4
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Re: Unity gain

A couple of videos I did a while back that you may find useful:

https://www.youtube.com/watch?v=pJWK...ature=youtu.be

https://www.youtube.com/watch?v=s7jG...ature=youtu.be
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Old September 7th, 2016, 06:18 AM   #5
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Re: Unity gain

In addition to the tone generator box in Gary's video, there are free software and phone apps available for generating, saving or recording sine wave 1kHz guide tones at various signal levels. These tones can then be used in the same manner as a physical tone generator box to set levels.

Definitely match the XLR output level of the mixer (Mic or Line) with the input level of the XLR connector on the camera. Also make sure the Phantom Power switch for that XLR input on the camera is set to OFF.

In addition, set the camera's audio limiter to OFF while you are setting the level using tone. Then engage the limiter before recording.

Having the limiter on the camera set to ON while setting levels can fool you into pushing the output of the mixer too high, which leads to an increase in the ambient noise during quiet passages and to a lot of compression from the camera's limiter circuit during "normal" sound levels.
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Old September 7th, 2016, 06:19 AM   #6
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Re: Unity gain

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Originally Posted by Kim Miner View Post
I have a Shure SCM268 four channel mixer and a Panasonic AG-AC130a. I'm having trouble doing unity gain. Does anyone have the same combination that could explain the steps? Thank you.
I'm not sure this is exactly what you are asking about, but maybe it will help. My mixer is an older Shure M267, but I think the outputs are about the same to yours, and my camera is a Canon XH-A1S, and this is how I set them up. I don't have a tone generator to check the full audio path, but can check the path from mixer to camera. This will give you a start.

1) I run bars and tone on the camera and take note of where the audio level is on the camera lcd screen. Then switch off bars and tone. Pretty sure yours has that function too.

2) Connect the xlr out on the mixer to one of the xlr in ports on the camera. Set the mixer to mic level output. I don't use the line level. Typically have another mic in the second xlr port of the camera. When I mix line level on one channel and mic level on another, weird things seem to happen. So I now set to mic level on both. Also, make sure phantom power is off on the port the cable from the mixer is plugged into.

3) Turn on tone generator of the mixer. Not sure where the knob is on yours. Note carefully where the audio level lies on the camera lcd screen. Adjust camera volume controls as needed so mixer tone volume level matches where bars and tone volume level was.

Hope this helps.
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Old September 7th, 2016, 09:07 AM   #7
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Re: Unity gain

I don't see any internal tone oscillator on the 268, so and external tone source would be wanted. Match output ( your mixer) to input (your cam) operating levels must be the same. Typically line or mic. Set the tone level so 268's output meter reads 0dB. Set the cam's record volume level to -20dB, If the cam's record volume is within 10 or 15% of all the up, or the way down, something's NOT set right.. likely a camera audio gain setting.
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Old September 7th, 2016, 06:26 PM   #8
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Re: Unity gain

Thank you for answering my question. I'm super new at audio, I'm video taping interviews with 4 lavaliere mics and having trouble synching up my mixer with my camcorder. I'm stumped on how to adjust the tone generator on my scm268 Shure mixer... can you " dumb it down" for me? Thanks!
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Old September 8th, 2016, 02:49 AM   #9
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Re: Unity gain

Did you watch the videos that Mr. Nattrass posted?
The Shure SCM268 mixer does not have an internal tone generator.
What are you using for the tone generator?
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Old September 8th, 2016, 05:43 AM   #10
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Re: Unity gain

Sorry for the confusion I inadvertently generated. While the older model M267 I've been using for years generates tone, the newer model does not. Looking at the manufacturer's site, the 268 is obviously the replacement for the 267 I use. Nearly identical. With one very important difference.

It never dawned on me that Shure would remove such a useful feature. With my hearing loss as I get older, the tone generation is crucial as a reliable calibration standard. I need to see where the levels are.

My apologies. Truly a case of "they sure don't make 'em like they used to."
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Old September 8th, 2016, 08:31 AM   #11
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Re: Unity gain

Most of the M series mixers I've encountered (starting with the M67) were in hotel banquet halls, where the A/V staff was.. technically challenged. (even in Midtown Manhattan hotels) So reference levels were rarely used or understood. So I sort of understand Shure's cost saving elimination.
In your case, a recording of a reference tone would suffice, either from an MP3 file on your smart phone, a 'tone plug' or in between white noise from a radio. FWIW, I prefer to use the less obnoxious 400Hz (Dolby) calibration tone, since the 'center' frequency (1kHz) is not a factor, as it was in the analog days.

Last edited by Rick Reineke; September 9th, 2016 at 07:54 AM.
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Old September 8th, 2016, 03:30 PM   #12
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Re: Unity gain

You can also get an APP for your phone that generates tone or pink/white noise.

I personally use this one: https://itunes.apple.com/gb/app/spln...355396114?mt=8

Video demo here:
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Old September 8th, 2016, 03:59 PM   #13
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Re: Unity gain

Kim,

Your not providing enough information to get the specific answers you want. Ther is too many variables. Like what model are the mics? Are they all the same? And what is happening, is the signal too hot or too weak? You have a signal mismatch some where. Start at the camera and work backwards making sure every device is set to mic level. Then play some kind of tone (as suggested into the mics.

Steve
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