Lippman@MIT-MULTICS.ARPA (03/19/86)
I could be wrong, but I vaguely recall that the recording standard of the Sony PCM-F1 PCM adapter for 1/2" and 3/4" VCRs is not quite the same as the format used on the digital audio disc. The clock rates are different, and the contain the option to record at an additional bit rate not used on the disc. I also vaguely recall that the PAL/SECAM version of these devices is similar. Neither generates the tape that is the original (pre-master) for the DAD process. That tape is generated by (among other things) a Sony PCM-1610, which accepts audio in and generate a digital signal that can be recorded on a 3/4" VCR. It contains the Pand Q codes needed for digital audiodisc control as well as the audio channels at the correct bit rate. It also generates SMPTE time code for controlling the mastering process. And, it decodes the signal if you wish. I believe there is an editing system either available or compatible with it that does better than 1/30 second editing (which is not good enough for professional audio use.) Beware that the output from the 1610 is incompatible withmany 3/4" decks and most 1/2" decks as well. The issue is precisely how many lines they record and when they do their head switching. Professional decks are a bit more comprehensive here. In either case, you will be hard pressed to tell the difference between the DAD signal and the tape signal. It is not gloriously good to be the "mastering device" for audiodiscs. Since mechanical tolerances are not a problem with this recording format (as they would be with analogue tape recorders), the only issue is error rate: Do you get the same bits off the tape that you put there, and how well do you correct for those that are lost? Your home VCR is not likely to be better than the disc in this regard and the audio signal could therefore be worse. If you are contemplating recording concerts and other live material where the fidelity of the recorder must be high, then use good tape and hope for the best. The digital recording will be first rate. --Andy