Hi, John,

Two interesting points in your message.

(1) Waveforms from two passes not matching.

I don't care how you do the two passes but the visible waveform will
depend to a large degree of the phase lock between the audio and the
sampling clock. Oh, there is no phase lock...ooops.

Remember, we're sampling for reconstruction via a reconstruction (low
pass) filter. One can achieve the same sound with different numbers
going in. I know that is a scary thought, but early on I noticed that
two passes did not look the same when I tried to match them (ahead of
the perturbation the second pass was attempting to fix--hopefully they
won't match at the perturbation).

Until I realized what was going on, I wasted a whole heap of time.

As far as tape-to-head contact I found an amazing solution for that.
First, I was amazed when I compared a ReVox A77 to a Sony APR-5000 back
in 1998 or 1999. There was no question in my mind about that, even
though the A77 did well with new tape back in its day.

The next comparison is more up in the air: Studer A810 to Sony APR-5000.
I think I experienced less stable azimuth on country-laning full-track
mono 7.5 in/s tapes on the A810 than on the APR-5000, but I did not do
extensive testing.

Then came the A80RC. That has solved the vast majority of tape-to-head
contact issues. I will admit to having a spare tension board and moving
away from the factory recommended settings from time to time to help
with a specific issue.

I realize the Technics machines have a closed-loop drive which, in
theory, should make them superior, but given my experience, if you can
find an A80, I'd go for it. While I have more APR-5000s, I find that the
A80s are used more and more. My big use of the APRs these days are
four-track and narrow-track tapes. I have one pair more-or-less
permanently set up as a 4-track inline player. The second pair is often
left outfitted with my problem-solving 4-channel 8-track head (the one
on the elevator). The fifth machine in the studio normally has NAB heads
on it, but I also use it as a prep/wind machine while something is
transferring on an A80. I have two A80s in the studio. One is 7.5/15
with an external calibrated azimuth knob. The other is for multiple uses
and has been modified for 3.75/7.5/15 and I have NAB, DIN, and 1/4 track
stereo as well as full-track mono play heads and several preamp cards
and a variety of EQ plug-ins (some home-made on Vero board). I have a
15/30 machine ready to be wheeled in as needed. All 1/4-inch.


Cheers,

Richard


On 2/9/2016 2:58 AM, John Haley wrote:
> I have had some practical experience with dubbing tapes in reverse and then
> reversing the digital file on the computer. After reversing the absolute
> polarity, the files were not identical by appearance, although close. It
> could be that a small azimuth error would do that. Upon listening, the
> sound was also close but not exactly the same, again possibly a very small
> azimuth error causing this difference, or perhaps it was the reversed
> playback thing. In every case, on the one project I am recalling, I opted
> for the forward play dub as sounding a little better than the backwards
> one.
>
> However, on really problem tapes where playback is physically difficult,
> like where the tape is physically deformed--stretched on one edge, is no
> longer in a straight line, that kind of thing, playing backwards can be a
> good tool. Getting good tape-to-head contact is the issue, and playing the
> tape backwards changes all the stresses and the physical aspects of how the
> tape is moving past the heads. I have even had a tape that was so deformed
> that just keeping it moving by the heads required "hands on"
> treatment--gently holding it on place with fingers (which you can do on the
> Technics 1500 series head design) while it played, making a number of
> passes this way, including reverse ones, and then assembling the music bit
> by bit on the computer, using only the pieces where "good passes" were
> obtained (i.e., where the tape to head contact was right). A ridiculous
> way to have to do something, and anything but efficient, but it worked,
> salvaging what was on an otherwise unplayable tape.
>
> Best,
> John
>
>
>
> On Tue, Feb 9, 2016 at 1:09 AM, Corey Bailey <[log in to unmask]>
> wrote:
>
>> I need to remind everyone that I never made a backwards copy of an encoded
>> (stretched) tape, regardless of the noise reduction employed. I was there
>> when the "to decode or not decode" controversy was at it's height. My
>> position was (and still is) to decode the original and re-encode the copy.
>> Reason: If you make a copy of an encoded tape without decoding it, the copy
>> will have baked in tape hiss that will ultimately not be affected by the
>> noise reduction when applied for final playback. Thus, the copy will be
>> nosier than if you decoded and re-encoded the copy.
>>
>> Cheers!
>>
>> Corey
>> Corey Bailey Audio Engineering
>> www.baileyzone.net
>>
>> On 2/8/2016 9:19 PM, Jeff Willens wrote:
>>
>>> Actually, that was the one thing I always heard you could NEVER do with
>>> Dolby encoded tapes -- dub them without decoding them.
>>>
>>> I'm going back 15 years or so to remember this, but it is possible I did
>>> not
>>> decode the Dolby on some of the analog copies I made, probably for test
>>> purposes. As I said, decoding backwards was not my preferred method, but
>>> no
>>> one seemed bothered by my concerns. I did the dubs per the request of the
>>> reissue producer. If there were residual decoding artifacts, I never heard
>>> them or heard about them from the others involved.
>>>
>>> On Mon, 8 Feb 2016 21:23:34 -0000, Ted Kendall
>>> <[log in to unmask]> wrote:
>>>
>>>
>>>
>>>> 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.
>>>>
>>>>
>>>>
>>>>
>>>> ----- Original Message -----
>>>> From: "Jeff Willens"<[log in to unmask]>
>>>> To:<[log in to unmask]>
>>>> Sent: Monday, February 08, 2016 1:22 PM
>>>> Subject: Re: [ARSCLIST] Playing reels backwards - separating myth from
>>>> fact
>>>>
>>>>
>>>> I should think the net gain depends on the type of music involved. Back
>>>> at
>>>> Universal, I was asked by a producer to make 1:1 analog copies of album
>>>> masters played in reverse to be sent out for mastering. The thinking was
>>>> exactly as you describe: sharper transients, better bass response and
>>>> definition,etc. Since these were all reggae albums from the 70s and 80s,
>>>> they felt it was worth the effort.
>>>>
>>>> In my own crude testing, I found that, aside from making sure the
>>>> channels
>>>> were consistent (something one can easily overlook), I also found azimuh
>>>> to
>>>> be the crucial factor in achieving any success, Many masters were Dolby
>>>> encoded, which gave me much pause, but no one else was concerned about
>>>> it (I
>>>> figured decoding between the two tape machines was the least of all
>>>> evils).
>>>>
>>>> Was there a difference? Hard to say. I believe there was a slightly
>>>> better
>>>> result from reverse transfer, but nothing drastic. And definitely
>>>> nothing
>>>> that couldn't be got with skillful use of modern compression and EQ.
>>>> =========================================================================
>>>>
>>>>
>>>
>>>
>>
>
--
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.