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Hello, Derek,

Ahh, the beloved cassette...where do I begin?

Perhaps the best place to start is to suggest that the cassette was 
originally thought of as a dictation and general purpose format, not a 
high-fidelity format. Considering the tolerances involved and the skill 
of mass-producing precision machinery back in the day when it was 
introduced it is a miracle that it worked as well as it did.

With assistance from Jay McKnight of Magnetic Reference Lab and a few 
others, I have written to blog posts on some of the ambiguity in 
high-frequency response. This was in response to the widely held myth 
that Nakamichi violated the equalization standard in order to make the 
cassette sound better when, in fact, it appears that they actually 
upheld the printed equalization standard while Philips et al made 
calibration tapes that did not meet the actual printed standard. This 
ended in an unspecific "Prague Compromise". The bottom line is a 4 dB 
ambiguity at 16 kHz.

http://richardhess.com/notes/2006/05/17/cassette-equalization-the-4-db-ambiguity-at-16-khz/
http://richardhess.com/notes/2010/10/08/cassette-equalization-redo/

Jay links to some of his papers within his quoted reply in the second 
blog post above, but his website is here
http://www.mrltapes.com/

As to EQ, references are provided in the 2010 blog post and Jay has 
material about EQ on his website.

A great reference (and order your copy now while a few inexpensive 
copies still exist) is Marvin Camras's "Magnetic Recording Handbook" 
ISBN 0-442-26262-0. I just ordered the copy from Better World Books, 
there are others. The best place to find the deals is www.fetchbook.info.

As to azimuth, I've done my best to attempt to describe and show the 
effect of badly adjusted azimuth here:
http://richardhess.com/notes/2006/09/27/azimuth-hows-and-whys/

You might find some useful information at this page
http://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/015-cassettes/

This might be of some interest but is not directly related to cassettes
http://richardhess.com/notes/2007/08/26/tape-speed-track-width-frequency-response-and-dynamic-range/

This refers to aligning a tape recorder, but note that MRL does not make 
cassette calibration tapes
http://richardhess.com/notes/2008/02/02/aligning-a-tape-recorder/

While not describing how bias really works (which is currently not 
properly described in most publications including Camras, according to 
McKnight and others) here is a sampling of bias frequencies.
http://richardhess.com/notes/2008/02/02/tape-recorder-bias-frequencies/

This discusses issues of mono cassettes and stereo reproducers
http://richardhess.com/notes/2008/05/22/mono-and-stereo-cassettes/
and was updated just now

This relates to azimuth and azimuth wander in 1/4-inch tapes. There are 
similar issues in some cassettes.
http://richardhess.com/notes/2012/01/06/playing-full-track-mono-tapes/

This applies to reels, but may offer some insight to the geometric 
issues that also somewhat apply to cassettes.
http://richardhess.com/notes/2012/01/06/capturing-both-directions-of-a-half-track-mono-tape/

This provides some insight into gap loss, but is not enough for a 
complete understanding.
http://richardhess.com/notes/2012/03/06/gap-length/

Another cassette issue:
http://richardhess.com/notes/2008/02/23/slow-speed-4-channel-cassette-digitization/

You might enjoy this travesty
http://richardhess.com/notes/2006/03/31/project-notes-advanced-oxide-delamination-of-a-cassette/

Another annoying cassette
http://richardhess.com/notes/2006/03/23/project-notes-crosstalk-on-a-cassette/

Issues with old machines
http://richardhess.com/notes/2009/09/02/dangers-of-old-tape-recorders-for-playback-using-the-elevator-head/

As to your last question about who should do it, any task worth doing is 
worth doing well and that means that experienced professionals should do 
the work. You have to start somewhere, so becoming an experienced 
professional is possible, but giving the work to an uninterested and 
inexperienced clerk is a certain invitation to failure, especially if 
there is no technical supervision. I know of one project that was 
supervised by someone who made it her business to learn and then had a 
bunch of volunteers actually coming in. She trained them as to what to 
listen for and when to call if they needed assistance. Thousands of 
tapes were successfully digitized. She started out by hiring me to 
assess the collection and then hired me for some additional training, 
but the bulk of the work was done by volunteers.

Cheers,

Richard


On 2012-10-28 2:56 PM, Derek J Jackson wrote:
> I am a long time listener, first time caller on this listserv. I am student
> looking for some help on research I am doing on the standard audio compact
> cassette. Specifically, I am looking for any information on the upper
> frequency limits a compact cassette could capture but in general I also
> wonder if there are some resources people may know of that explain some of
> the essential, but more technical, characteristics of cassettes and cassette
> recorders (e.g. alignment, tape bias, equalization, gap loss.) I seem to be
> at an intermediate stage where most of the resources I find are too general
> and donít give me any new information, or so technical that I have
> difficulty making sense out of them. I would really appreciate it if anyone
> could give me information about what factors limit the ability of cassette
> tape/recorders to record high frequencies, and some idea of what that limit
> might be for standard commercial equipment and tape? And/Or more generally
> point me to any resources that might help me understand some of the more
> technical aspects of cassette recording and tape characteristics.
>
> And while I am at it I may as well solicit your opinions on digitizing
> cassettes. I have read several case studies of institutions digitizing their
> own cassettes, but then I have also read the IASA TC reports, Sound
> Direction, ARSC TC guidelines, etc. and these reports would indicate that
> digital transfers should always be done by audio professionals. What do the
> folks here think? Is there some middle ground? On a format as ubiquitous as
> the compact cassette is it conceivable that an institution could responsibly
> do its own digitization work? Just trying to sort it all out.
>
> Any help is greatly and kindly appreciated.
> Best,
> Derek Jackson
>

-- 
Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada           (905) 713 6733     1-877-TAPE-FIX
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.