Yes, this was the analog era and only MONO or 2Tr masters were involved.
The 1970's-1980's, in fact, and many people on this list probably bought
vinyl that was produced form one of those backwards copies.
Other "out of the box" thinking at the time led to disabling the erase
head for first-pass on virgin tape to help the signal-to-noise ratio.
This was accomplished by switching the erase voltage to a dummy head so
that the load remained the same on the erase amp. Even tried this with
2" multitrack recording with improved S/N results but then, the mixer
du-jour would forget to turn on the erase head when needed and record
sound-on-sound for a punch-in so, the multitrack innovation was abandoned.
On 2/7/2016 12:43 PM, Richard L. Hess wrote:
> Hi, Corey,
> Very interesting.
> Just to be crystal clear, you were making analog to analog copies.
> Absolute polarity in that case is a non-issue as there are, in effect,
> two polarity reversals. The first one when you play the original tape
> backwards and the second when you play the backwards-recorded tape
> forwards (in essence backwards again).
> Obviously, one needs to flip the polarity in the digital domain as the
> file reversal should not include a polarity reversal, although if the
> function were designed for this purpose it COULD do both in one pass,
> but I don't think any do.
> Your results are in keeping with what I have heard for analog copies
> and I think since we are concatenating two complete passes through the
> analog tape chain that there is more of a reason to say this is good
> for analog copies than for digital copies.
> I really hope Tom (or someone) does some listening tests. I've done my
> share recently with the Satin software NR decoder.
> On 2/7/2016 3:03 PM, Corey Bailey wrote:
>> I used to routinely transfer 2 track music masters backwards. The
>> results were noticeably better than a transfer made forwards. The tapes
>> were non-Dolby encoded (I was never a fan of noise reduction for music
>> recording). Azimuth is absolutely critical. It has to be spot on as well
>> as the playback EQ calibration. This process was always done on the same
>> machine that recorded the master tape. Azimuth and playback EQ are
>> calibrated with the tape playing forward and then the tones are played
>> in reverse, recorded and observed. If there is any difference in the
>> recorded level of the source tones on the reverse copy, then the
>> playback alignment has to be re-checked and the culprit is usually
>> azimuth. I always adjust azimuth with a dual trace scope and overlap the
>> channels to insure absolute phase although there are a few ways to
>> calibrate azimuth and get it right. When it comes to the absolute
>> polarity of the copy, it was never an issue because the phase
>> relationship remains the same if all is adjusted properly, even though
>> absolute phase is reversed. Did many A-B listening tests with everyone
>> concerned and an overwhelming majority preferred the backwards transfer.
>> Those who weren't sure could usually not tell the difference. Then, of
>> course, there were those nervous producers who were afraid of anything
>> outside the box.
>> I have never tried this with 1/4 track or 4 channel formats and Richard
>> Hess makes a valid point about the difference in 4 channel heads vs. 1/4
>> track. I did try the process on a 2" 24 track tape and the results were
>> not great and I have to reason that it was an azimuth issue because
>> multi-track heads are never perfect. The 2" transfer was tried on an
>> AMPEX MM1200 which are fixed azimuth machines.
>> Corey Bailey Audio Engineering