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Hi, Bill, <br>
<br>
That is fascinating! <br>
<br>
One very minor nit: the comparator only works on the right channel
of the currently playing side. It is actually a six-channel-ish play
head. The left (outer) channels are normal and the right (inner)
channels are split--series-connected for the audio.<br>
<br>
The LVDT is a wonderful solution. <br>
<br>
Do you happen to have the displacement of the azimuth adjuster
ribbon to arc-minutes conversion factor data?<br>
<br>
I have made a modification to the Dragon as I find with many
problematic tapes, the auto system doesn't work as well as one would
hope. This modification is simple. I cut the wire that is the
ungrounded feed to the azimuth motor. I run it through a spare pole
on the Timer Play/Rec switch so that when that switch is in the Rec
mode, the auto azimuth is defeated and the motor's feed is switched
to a pin on the Gizmo connector. Since the Gizmo connector has a
bipolar power supply, I simply extend a 4-pin DIN cable to a small
Hammond diecast box with an (on)-off-(on) [(on) means momentary]
switch with a series resistor. So, I can remotely pulse the azimuth
motor forward and back while watching the stereotool.com azimuth
display. <br>
<br>
I do find tapes that are outside the range of the electrically
adjusted azimuth so I manually adjust the azimuth with the
electrical version centred and then reset the manual adjustment
later (or use an MR-1 and manually adjust).<br>
<br>
The other modification I've thought about for a while (but haven't
done) is to replace the remote connector (which I'm afraid to use
since the logic chip could be damaged by static and I hear it's
unobtainable) with a 5-pin DIN connector and run that to the head
preamp outputs before the CMOS switches so that audio from both
sides of the tape are brought out simultaneously from that wonderful
Nakamichi play head. My intent here would be to use a standard DIN -
4 RCA cable and RCA to TS adapters and use the four instrument
inputs on my nearby RME Firefaces to provide the additional gain and
do whatever else is needed in software. But I don't have enough call
for four track HiFi cassettes. I can use my DATATape CMS1000 tape
players for court reporting type of stuff (they do 15/32 to 7.5
in/s), but are not as HiFi as the Dragon.<br>
<br>
And, I previously mentioned always using the outboard Dolby 422 when
needed rather than the inboard decoder so that I can easily adjust
the playback level into the decoder to calibrate it. Someday, maybe,
my colleague John Dyson will do a Dolby B/C decoder...I hope.<br>
<br>
Cheers,<br>
<br>
Richard<br>
<br>
<br>
<div class="moz-cite-prefix">On 2020-02-11 10:31 p.m., Bill Whitlock
via ProAudio wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1087446044.1270580.1581478319500@mail.yahoo.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div style="color:black;font: 12pt Arial, Helvetica, sans-serif;">Not
wanting to digress too far, but your mention of the Nakamichi
Dragon again reminded me of my years at Capitol. Capitol was
unique in the cassette and LP business because they were so
highly vertically integrated. They manufactured their own tape,
molded their own cassette shells (or C-zeros as they were
called) - and even their own lacquer master discs. Part of QC
for the cassette shell molding operation involved using modified
(in my electronic development lab, which was not located in the
"tower" BTW) Dragons to measure azimuth accuracy and
consistency. The auto-azimuth mechanics was fitted with an LVDT
linear transducer which then drove a large zero-center analog
meter reading +/- 10 arc-minutes full-scale. The shells were
generally excellent except when someone shortened the cool cycle
on the injection-molding machines, which caused the shells to
warp slightly. And, for those unfamiliar with the Dragon, the
azimuth-adjusting mechanism was driven by a closed-loop servo
that measured phase difference between signals from the two
"sub-heads" on each track. It was a wonderful tool for QC.
<div><br>
</div>
<div>We also developed a super-low noise LP player to measure
noise floor of lacquer master discs to help with lacquer
additive formulation. Another player measured the increase
(and once-around variations) in tracking force caused by
electret charges on the surface of vinyl records created
during the pressing operation. The staff rheologist (plastic
expert and formulator) used it to test new "anti-static" vinyl
additives.</div>
<div><br>
</div>
<div>My 7-year stint at Capitol was fascinating because of their
heavy investment in R&D - but, by the nineties, they'd
pretty much become just another record label.</div>
<div><br>
</div>
<div>Bill Whitlock</div>
<div>Whitlock Consulting</div>
<div>Ventura, CA<br>
<br>
<br>
<div
style="font-family:arial,helvetica;font-size:10pt;color:black">-----Original
Message-----<br>
From: Mike via ProAudio <a class="moz-txt-link-rfc2396E" href="mailto:proaudio@bach.pgm.com"><proaudio@bach.pgm.com></a><br>
To: proaudio <a class="moz-txt-link-rfc2396E" href="mailto:proaudio@bach.pgm.com"><proaudio@bach.pgm.com></a><br>
Sent: Tue, Feb 11, 2020 5:23 pm<br>
Subject: Re: [ProAudio] FeralA - Recordings released encoded
with Dolby A<br>
<br>
<div dir="ltr">Just a side note about Dolby cassettes:<br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Corey Bailey Audio Engineering<<a
ymailto="mailto:proaudio@baileyzone.net" rel="noopener
noreferrer" href="mailto:proaudio@baileyzone.net"
moz-do-not-send="true">proaudio@baileyzone.net</a>>
wrote:<br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">> IIRC, it was Dolby B. Could have been
"C" because, at the time, I used<br>
</div>
<div dir="ltr">> whatever was built into the record deck
& was compatible with my car<br>
</div>
<div dir="ltr">> stereo so that I could switch the NR
off.<br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">I reviewed a Marantz cassette deck last year,
looking for something I <br>
</div>
<div dir="ltr">could recommend to the home-archivists who
want to digitize the closet <br>
</div>
<div dir="ltr">full of cassettes of their band's shows from
30 years ago, but who no <br>
</div>
<div dir="ltr">longer have a means to play them and wouldn't
spend the bucks on a <br>
</div>
<div dir="ltr">restored Dragon. It has a Noise Reduction
switch (for playback only), <br>
</div>
<div dir="ltr">but no B/C switch. I asked their tech support
about it, assuming that it <br>
</div>
<div dir="ltr">was Dolby B, and the answer was that it works
for either B or C.<br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">I didn't have a good way of testing how good
of a job it did on either - <br>
</div>
<div dir="ltr">the best I could do was to compare playback
in the Marantz with that of <br>
</div>
<div dir="ltr">my TASCAM 112Mk2, but with several other
significant differences between <br>
</div>
<div dir="ltr">playback on the two decks, I couldn't really
evaluate the NR decoding.<br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">It turns out that what's in the Marantz (and
also in an almost identical <br>
</div>
<div dir="ltr">deck from TASCAM) is that it's not really
Dolby, because there are no <br>
</div>
<div dir="ltr">more Dolby decoder chips available, and
that's what was used in all the <br>
</div>
<div dir="ltr">cassette decks. This decoder circuit was
something that was developed (I <br>
</div>
<div dir="ltr">don't know by who) to approximate the Dolby
playback - one size "fits" <br>
</div>
<div dir="ltr">all - though I suppose not Dolby S.<br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">-- <br>
</div>
<div dir="ltr">For a good time call <a target="_blank"
rel="noopener noreferrer"
href="http://mikeriversaudio.wordpress.com"
moz-do-not-send="true">http://mikeriversaudio.wordpress.com</a><br>
</div>
<div dir="ltr">_______________________________________________<br>
</div>
<div dir="ltr">ProAudio mailing list<br>
</div>
<div dir="ltr"><a ymailto="mailto:ProAudio@bach.pgm.com"
rel="noopener noreferrer"
href="mailto:ProAudio@bach.pgm.com"
moz-do-not-send="true">ProAudio@bach.pgm.com</a><br>
</div>
<div dir="ltr"><a target="_blank" rel="noopener noreferrer"
href="http://bach.pgm.com/mailman/listinfo/proaudio"
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<br>
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<br>
<pre class="moz-signature" cols="72">--
Richard L. Hess email: <a class="moz-txt-link-abbreviated" href="mailto:richard@richardhess.com">richard@richardhess.com</a>
Aurora, Ontario, Canada <a class="moz-txt-link-freetext" href="http://www.richardhess.com/">http://www.richardhess.com/</a>
<a class="moz-txt-link-freetext" href="http://www.richardhess.com/tape/contact.htm">http://www.richardhess.com/tape/contact.htm</a>
Quality tape transfers -- even from hard-to-play tapes.</pre>
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