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Re: [ARSCLIST] Cassette playback (was Can 78s sound better than LPs?)
At 07:45 AM 8/26/2006, Tom Fine wrote:
Hi Lou:
This has been discussed, I think on this list, but it was a while
back. You are a good businessman! It is VERY smart to have a client
bring in his deck if it's a Nak. Nak has some non-standard things
with Dolby (non-standard = not compatible with other manufacturers).
If you have, say, a Nak Dragon, you should be able to reproduce his
tapes perfectly (and then some since the Dragon's transport is more
stable), but if his portable got dropped a few times, it might have
unique azimuth and speed issues all its own. I forgot the
particulars, but I think some argue that Nak is the only one who
followed the Dolby B standard to the letter while everyone else
didn't, but whatever the reason, Dolby B tapes made on another deck
can sound wrong played back on a Nak and vice-versa. Not all the
time, but sometimes. I'm hoping Richard Hess pipes up with the
technical particulars on this.
<humour>
E
P
I
P
(is that what you meant by pipe up? It reads from bottom to top)
</humour><serious>
It's a multi-faceted problem, really.
My personal experience is that tapes on made on my Nakamichi 550 (the
portable one--there may have been another and I no longer have it)
and on my Sony TCD-5M (which I still have) sound better to far better
when reproduced on the Dragon.
As far as I can determine, there was no separate Dolby standard at
all, though I must confess that even on some of my tapes, suspected
to have been made on the Nak 550, there is Dolby mis-tracking -- more
about that later.
The root cause of Nakamichi and other cassette machine
incompatibilities is (I hope) clearly explained here:
http://richardhess.com/notes/2006/05/17/cassette-equalization-the-4-db-ambiguity-at-16-khz/
Jay McKnight and I spent a fair amount of time looking at this and
discussing it (Thanks, Jay). Other pillars of recording were also
brought into the discussions that resulted in this document, and are
credited in it.
Since there is an ambiguity that is substantial as far as Dolby is
concerned, it might be possible to place a filter set between the
reproducer and the Dolby decoder to make things happier. However,
there is little guidance available for adjusting that filter set.
My procedure for dealing with obviously mistracking Dolbys is to use
my outboard Dolby 422 decoder (4 CH of B/C/S - watch out, the S card
was optional and its presence is determined if the S light
illuminates with S mode selected) is as follows:
Make sure your outboard Dolby decoder is calibrated so that there is
some headroom or reach on the player output knob - My Dragons provide
nominal output via the Aphex balance boxes with the output controls
about 3 o'clock. Then, with one hand on the Dragon output control and
the other on the monitor level control, I adjust them to maintain
constant listening level while listening for Dolby artifacts.
Usually, at some point, the Dolby artifacts are minimized. That's
where I do the transfer.
This Dolby mistracking can be caused by other things than the 4 dB
ambiguity at 16 kHz. One thing that a friend noticed when he was
working in the Standard Tape Lab was that it appeared that some
cassettes would spontaneously lose highs over a one-year period. He
never understood why, but his tests seemed to indicate that it was
happening and he's convinced that it happened. While a 10 dB loss at
20 kHz would be very bad, this might happen to a lesser extent with
other tapes. His job at the time was evaluating tapes for a major
tape manufacturer and I did ask him about the usual suspects which he
felt were not at issue.
So, yes, cassettes are not the best medium, but I think I've summed
up their application in my blog entry, cited above.
Cheers,
Richard
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.