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I use software to help me align azimuth on cassette transfers all the
time in conjunction with my ears.  You can call it a "crutch" or you
can call it being thorough and professional.

Consider that you could theoretically calibrate a reel machine by ear,
too, but I wouldn't hire anyone that didn't use a voltmeter or DAW
meters.

On Wed, Sep 10, 2014 at 9:01 AM, Richard L. Hess
<[log in to unmask]> wrote:
> I probably should clarify...
>
> Think of the azimuth error situation as a right triangle.
>
> The "perfect" azimuth is one leg that is vertical. The actual recorded
> azimuth is the hypotenuse. The azimuth error is the leg which is horizontal.
>
> The length of the horizontal leg of the triangle can be translated into the
> time delay and the phase shift between the two channels.
>
> When the two channels are summed, even small errors which CAN be equalized
> out, grow into huge errors and cannot be recovered, so the re-timing between
> stereo channels prior to summing will produce far better results than not
> using it and summing the two channels will reduce the noise taken from
> either channel.
>
> For high-quality music work, using a full-track head is superior, but for
> oral history production work (especially from cassettes) there is merit to
> summing the two tracks, especially because mono cassette machines are hard
> to find and few (if any) were made with the quality of the top stereo
> machines.
>
> Here is an example using a cassette:
>
> 15 arc minutes (1/4 of a degree) azimuth error.
>
> Single channel  -3 dB point ~  9 000 Hz
> Summed channels -3 dB point ~  3 400 Hz
> Single channel  -6 dB point ~ 12 000 Hz
> Summed channels -6 dB point ~  4 600 Hz
>
> Sliding the second channel in time to be in alignment with the first
> provides a huge improvement in the high-frequency response.
>
> I contend that, if desired, losses of up to approximately 6 dB can be
> equalized out as long as there is no additional boost and a rolloff after
> the - 6 dB point (to avoid increasing noise).
>
> Cheers,
>
> Richard
>
>
>
>
> On 2014-09-10 10:25 AM, Richard L. Hess wrote:
>>
>> Hi, Andrew and Tom,
>>
>> I am (very) slowly working towards a paper on azimuth.
>>
>> The full-track mono tape is, of course, the hardest to play from an
>> azimuth perspective (of the common formats)--I hate to think about the
>> 1-inch two-track!
>>
>> Transport guidance is a huge issue and I have found that the Studer A80
>> is magical in that regard--and the Studer A810, not so much. The Sony
>> APR-5000 is between the two.
>>
>> For those of us who have taught ourselves how to adjust azimuth by ear
>> (sort of the same thing as focusing a camera lens in many ways), we do
>> not need crutches, but I have come to realize that using a two-track
>> head for "factory workers" might be beneficial.
>>
>> For one project I proposed (but we chose not to implement) a wide/narrow
>> head for full track mono. We batted around a few different
>> configurations--including a long discussion with Greg Orton. I was
>> thinking of something like 0.120 and 0.04. The nice thing is even if
>> things go south, you still have a good percentage of the highs on the
>> 0.04 track, albeit noisy.
>>
>> With that said, for oral history cassettes, I use, in addition to manual
>> azimuth adjustment, the azimuth compensation feature of
>> www.stereotool.com. This allows excellent channel summing for improved
>> noise, assuming both channels were recorded.
>>
>> There is a similar feature in iZotope RX Advanced.
>>
>> Cheers,
>>
>> Richard
>>
>
> --
> 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.