Date:         Sat, 26 Aug 2006 11:52:42 -0400
Reply-To:     Association for Recorded Sound Discussion List
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Sender:       Association for Recorded Sound Discussion List
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From:         "Richard L. Hess" <[log in to unmask]>
Subject:      Re: Cassette playback (was Can 78s sound better than LPs?)
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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: [log in to unmask]
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.