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In Reply to: RE: don't record hot in digital posted by Joe Murphy Jr on March 24, 2012 at 21:07:33
... there seem to be exceptions. My only experience burning digital from analog sources is via a Tascam CD-RW700 recorder. While I always try to keep recordings out of the "red," there have been occasions where I slipped up. In some cases, REALLY slipped up. But after listening to the finished product, I have never detected anything harsh-sounding and have been wondering why. Just lucky?
Follow Ups:
It depends on what is clipped and how long. If a single drum hit is clipped for a few samples it will be inaudible. If a steady tone is clipped for multiple samples on multiple peaks of the waveform it will be audible if there is other music going on at the same time that is effectively "muted" while the clip is in effect. Generally it is possible to suspect something is wrong on a single clip in a classical orchestra climax. However, often this suspicion proves to be incorrect after inspecting the actual waveform. Sometimes several clean acoustic waveforms peak simultaneously and result in distortion in ones ear. (This can be experienced at live orchestra concert if one sits in front rows.)
There is software, such as iZotope RX, that can do a fairly good job of correcting clipped waveforms by "faking" the missing content. This will fool the ear if this is done sufficiently infrequently, so sometimes this works to fix a bad recording.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
There's a soft-clip circuit or limiter in the signal path. It would be set to only spring into action very close to 0dB.
0dB on the meter really isn't 0dB, but maybe a few dBs lower. I've seen peak levels levels on cassette tapes that I've recorded show up above and below my decks meter reading when played back on other tape decks.
What it has to say on the subject: "The red OVER indicators on the meters should never light. Unlike analog equipment, digital audio units produce extremely unpleasant sounds when distorted and there is no 'headroom' after the 0 mark."
After 10 years, still waiting for its CDs to emit any "extremely unpleasant sounds," so I guess I HAVE been lucky, given all the times the red OVER indicators have lit.
Thanks to you both.
If the cassette deck is playing a tape that is reading around 0 on the dec's VU meter then you will want the digital peak levels to be around -11 dBfs or even a bit lower if you are using metal tapes, as these can easily put out undistorted +10 analog signals.Soundforge has a mode for it's "channel meters" that provides a variety of VU scales that average over a short period. The best one to use is the Nordic PPM. If it's reading above 0 VU it gives a warm feeling of "loud enough" while still retaining substantial head room. Other editors may have similar capabilities.
You can make up a calibration tape of band limited pink noise, that you can get from Bob Katz' web site. Record this on the tape at 0 VU and then adjust your recording gain so that you get the same levels on a copy you make of the cassette tape as you get when you play the original file you downloaded. I believe this will work for all but the very hottest cassette tapes, but I haven't tried it because I'm not set up to record on my deck at present, so let me know if this doesn't pan out.
I list various ways of approaching this problem not because it is necessary to use all of them, but to give a feel for what might be available. There is even a better system that Bob Katz advocates and that is to ignore all the meters completely after calibrating one's speakers to a fixed setting. Then when one makes a recording (e.g. does a transfer) one simply adjusts the volume one hears in one's speakers until it sounds "right". One needs his test file and a Rat Shack SPL meter to set up the system plus repeatable settings on one's volume control.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Edits: 03/26/12
... I've used the Tascam only to record from vinyl and off-air from a tuner.
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