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I don't understand the virtue of playing the tape back on the same machine it was recorded on; any professional machine has separate record and pb electronics and heads so essentially they are two different machines anyway, except for the transports. db Sent from my iPhone > On Feb 9, 2016, at 1:09 PM, Doug Pomeroy <[log in to unmask]> wrote: > > It's been many years since I have thought about this subject. Back in > 1983 R-e/p magazine printed a letter I wrote in response to an article by > John Roberts about playing tapes backwards and the possible improvement > in transient response. Concerning the requirement that the tape be > played backwards, ideally on the same recorder which recorded it, this > means a second recorder was needed to capture the reversed audio and > that tape, when flipped, produced a phase-corrected tape running in the > normal direction (a digital processor could be used for the second reversal, > avoiding the losses connected with making an analog copy). > > There is a letter in the Journal of the AES (1968, p 112, which I no longer > have) by J.W. Beauchamp which discusses this topic. He says "the Fourier > transform of a time-reversed signal is the complex conjugate of the signal > in forward time". I noted that British engineer Tony Faulkner reverse-records > his analog tapes, according to a news item in Studio Sound magazine in 1977, > which interestingly identifies this as being "an early American technique". > > Doug Pomeroy > Audio Restoration and Mastering Services > 193 Baltic St > Brooklyn, NY 11201-6173 > (718) 855-2650 > [log in to unmask] > > >> On Feb 9, 2016, at 12:00 AM, ARSCLIST automatic digest system wrote: >> >> Date: Mon, 8 Feb 2016 21:23:34 -0000 >> From: Ted Kendall <[log in to unmask]> >> Subject: Re: Playing reels backwards - separating myth from fact >> >> This runs counter to my own experience. Firstly, one great benefit of Dolby >> A was that straight copies of encoded tapes could be made without decoding, >> provided that the reference tones were retained on the copy, so there was no >> need to decode as part of the dubbing process. Secondly, to decode a Dolby A >> tape on reverse play is just plain wrong - the attack and decay >> chracteristics of the system are asymmetrical, so the decoding will be >> wrong, no matter how much you have finessed the other parameters. > > Doug Pomeroy > Audio Restoration and Mastering Services > 193 Baltic St > Brooklyn, NY 11201-6173 > (718) 855-2650 > [log in to unmask]