Setting tape recording levels is a tradeoff between distortion and noise. VU meters are different from peak reading digital meters, it gets tricky To find ideal recording levels but for home use with dolby I always liked To use good tape and err on the side of recording too low rather than Recording too high a level. Hiss I could tolerate, distortion, not so much.
-----Original Message----- From: pdml-boun...@pdml.net [mailto:pdml-boun...@pdml.net] On Behalf Of Mark Roberts Sent: Friday, February 03, 2012 7:28 PM To: Pentax-Discuss Mail List Subject: Re: OT question for electronics geeks John Francis wrote: >I'm pretty sure the meters on my tape decks, etc. all had a "0" >setting around 3/4 of the way along. On the old mechanical ones >the area behind the needle past that point was painted red; on the >later electronic ones that was where the colour of the indicator >lights changed from green to red. > >The zero point was where the best signal-to-noise ratio could be >attained. Conventional wisdom said you tried to keep sustained >recording levels below that point, but as close to it as possible; >occasional (brief) peaks into the red were OK. > >[Very much like "exposing to the right" by using the histogram] Wow. A lot of nostalgia here! Being a bit of an audio geek (and working as a technician in recording studios) I did a lot of tape deck calibration. The "0" point was supposed to represent a specific level of magnetization of the tape, which was determined by the tape manufacturer, IIRC by measuring distortion levels as the signal level approached saturation (the magnetic tape equivalent of 255-255-255 RGB clipping in a digital image). The thing is, this was different for every specific tape formulation. What a pain it was dealing with all the different tape types! Of course, at the recording studio we just standardized on one single tape and I'd just have to align the machines at the start of every new project. You'd start with a lab-calibrated alignment tape (very expensive) and get the playback calibrated. They you'd make recordings and play them back, adjusting the recording settings until you get the correct playback characteristics. The thing was, the manufacturers kept improving tape formulations. Ironically enough, this was happening at the fastest rate during the final years of analog recording tape manufacture by 3M. It seemed that every year there would be a new formula that could take a stronger signal before saturation - say, an extra 3dB. Now since the lab-made calibration tape was a fixed standard, you'd have to calibrate playback levels to -3db as shown by the meters (the tape came with instructions for the exact level) and then re-calibrate the *meters* to show that new level as 0db. And then re-calibrate recording levels (which would work out 3dB hotter). In the end I think we were calibrating to be hitting the tape 9 or 12 dB hotter than the reference tape and still not coming near saturation with the tape formulations in use! So 0dB in tape recording was very far indeed from a fixed standard! -- Mark Roberts - Photography & Multimedia www.robertstech.com -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
