I will carve out some time later this week to run full-track and 2-track tapes forward and backward
and we can compare the audio. I'll put raw transfer audio up, so you can analize and process as you
see fit. I have to find some appropriate full-track material, probably will use session audio from
TV commercial soundtracks, made at A&R Studios in the 70s. For 2-track, I'll use an old Mercury 1956
duped stereo jazz tape, probably Max Roach so we can look at how percussive and trumpet wavefronts
behave. I have to change some things around in the studio setup to do the Quad tapes, so I'll hold
off on that until all the tapes arrive. For that project, I also have to get over to my locker and
get my two Dolby B playback units, because some of the tapes (not those I was wondering about
running backwards) are Dolby B encoded.
-- Tom Fine
----- Original Message -----
From: "Corey Bailey" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 08, 2016 12:39 AM
Subject: Re: [ARSCLIST] Playing reels backwards - separating myth from fact
> Hi Richard,
> 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