Subject:Audio Clibration

Posted by: jport

Date:6/7/2002 7:36:31 PM

I was wondering if someone could help with some guidelines on how to calibrate my audio settings so they match when I bring .wav files into other apps and record to tape.

I'm currently using a 1khz tone generated from SF6.0's SimpleSynthesis to calibrate, but I'm not getting the results I want. There must be something I'm doing wrong???

Subject:RE: Audio Clibration

Reply by: rraud

Date:6/7/2002 8:40:03 PM

Set your reference tone to around -14 to -20db on SF. This is refered to as: "digital zero, full scale" (fs), and should coresponde to "0-VU", meters usually found on most analouge tape machines and mixers.

Subject:RE: Audio Clibration

Reply by: pup

Date:6/10/2002 7:25:26 AM

rraud,

That's some good info. I was wondering about that. I've been using peak meters for so long now that I'm pretty clueless on the proper way to use a VU meter. I edit dialogue for radio infomercials, and I usually process my files to keep the voices hovering near 0 in Sound Forge for maximum volume. According to what you just wrote, my shows would be in the red on a VU meter, which would freak me out, as red usually means "uh-oh." You can see why I'm confused, no? Any insight on this.

- pup

Subject:RE: Audio Clibration

Reply by: rraud

Date:6/10/2002 9:38:06 AM

In the digital format like Sound Forge you must not exceed 0db no matter what. In the analouge format, it's perfectly normal and okay to peak around +2 or +3 or even higher depending on your tape or devices. On our analouge 2" tape multi-tracks I set the machines to run @ +6db over a 185nWb reference level. (some engineers go to +9!) If I did not calibrate the VU meters to match that level, they would be pinning most of the time. Let your ears be the judge.
I hope this makes things a little clearer for you. Maybe someone else can explain it better.

Subject:RE: Audio Clibration

Reply by: jport

Date:6/10/2002 6:15:30 PM

Thanks for your helpful suggestions. But how do you calibrate for multiple devices? I have a digital BetaCam deck that reads 0db, a DAT machine that reads -12db, a VHS Deck that reads +3db, and a Non-linear editor that reads -5db. To top it all off Sound Forge is calibrated at -6db. These db's are based on the 1khz tone I use.

I play it by ear when I record because what may be good on one machine may be to high or to low on another.

I have a Video/Audio distribution Amp, 1 V/A input and 4 V/A output, to make my recordings. My sound card is an Antex Studio Pro Card, the sliders for audio output are usually set to the middle range. I'm alway having to adjust these sliders when I should be treating them as a "Master out".

Subject:RE: Audio Clibration

Reply by: rraud

Date:6/11/2002 6:24:23 PM

You are running a lot of devices which more than likley are at different operating levels. I'm sure the digi-beta deck is +4 but your VHS & cassette may be -10. +4 balanced ins and outs on video tape machines "usually" have XLRs if it's +4, and RCA (phono)connectors for un-balanced -10. I don't know what your sound card is out-putting. Adjust your input levels on your machines, and if it sounds good than your doing something right.
PS- VU meter ballistics on VTRs are notoriously different from one another, so program material that may peaking at 0VU on one machine may be hitting +3VU or higher on another, both being set at the same 0VU 1kHz standard reference level. I run into this all the time on multi-camera/VTR iso shoots.

Subject:RE: Audio Clibration

Reply by: jport

Date:6/12/2002 10:08:12 PM

Thank you very much for your help? I thought there might be a way to calibrate everything.

I guess playing by ear is the best way to calibrate.