Gain structure: dBu, VU, dbFS - Page 2 at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.


Reply
 
Thread Tools Search this Thread
Old May 22nd, 2011, 02:08 PM   #16
Major Player
 
Join Date: Feb 2011
Location: San Francisco, CA
Posts: 416
Re: Gain structure: dBu, VU, dbFS

After having used the mixpre a little bit I'm seeing its limitations and wondering if a 302 or mixpre-d might work better for me. But that inspired me to research a bit more and find out there's no single ideal solution.

With a multimeter I measured the output with my custom-adjusted cable on the mixpre at a level of -32dbu (when the mixer outputs a 1khz tone nomincally at 0dbu). That is the level I had determined is best to align my 60d camera's 0dbFS point with the mixer 20dbu output level, so that the mixer limiting happens right before clipping, with the 60d camera preamps all the way down.

But it looks like using any other attenuating scheme, other than my custom cable for the mixpre, would be nonideal in that I would have to turn up the camera preamps more because the 302 or mixpre-d can't natively output a -32dbu signal. The DSLR level output on the mixpre-d is fixed at -36dbu, and the 302 has a dead zone where it can't be adjusted for output between -16dbu and -40dbu. So I'd have to turn the noisy camera preamp up by 4db with the mixpre-d, or 8db with the 302. Probably not a dealbreaker, but I'm concerned about the difficulty of remembering and verifying that my camera preamp level is set correctly every time I shoot, given that the scale is unmarked and I would have to remember something like "adjust all the way left then ten clicks to the right".

The SEScom cable incidentally produces an output of -42dbu from the mixpre, so it would require 10db increase on the camera.

I am curious to hear how others handle this issue, especially how people got the levels matched while using a 302 with a DSLR, or how they are planning to match levels with the Mixpre-d and a DSLR.
Tom Morrow is offline   Reply With Quote
Old May 22nd, 2011, 02:34 PM   #17
Major Player
 
Join Date: Feb 2011
Location: San Francisco, CA
Posts: 416
Re: Gain structure: dBu, VU, dbFS

As a reminder to myself: It looks like feeding the sescom cable from the XLR outputs would increase the output by 10db making it just perfect in level for me, and this could be a good option for someone who just wants to buy something off the shelf and not hassle with adjustments. But finding and living with the adapters/cables to convert the 1/8" to XLR might be annoying.
Tom Morrow is offline   Reply With Quote
Old May 24th, 2011, 04:18 AM   #18
Trustee
 
Join Date: Aug 2008
Location: New York
Posts: 1,842
Re: Gain structure: dBu, VU, dbFS

The 302's XLR outputs are variable all the way down to -50dB (or -60) via the software menu.
Rick Reineke is offline   Reply With Quote
Old May 27th, 2011, 02:29 AM   #19
Major Player
 
Join Date: Feb 2011
Location: San Francisco, CA
Posts: 416
Re: Gain structure: dBu, VU, dbFS

Yes IIRC the 302 can gain down all the way from -40 to -56dbu but unfortunately can't gain down from -16 to -40dbu.

The more I think about this maybe it's not worth worrying if I have to boost the camera's gain by 8db. I could always do a test recording and see how that changes the noise floor as opposed to my cable.
Tom Morrow is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 03:12 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network