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Path: utzoo!watmath!watdcsu!herbie
From: herbie@watdcsu.UUCP (Herb Chong [DCS])
Newsgroups: net.audio
Subject: Re: 2 questions, 2 replies
Message-ID: <1055@watdcsu.UUCP>
Date: Sat, 2-Mar-85 14:28:43 EST
Article-I.D.: watdcsu.1055
Posted: Sat Mar  2 14:28:43 1985
Date-Received: Sun, 3-Mar-85 04:38:53 EST
References: <173@encore.UUCP>
Reply-To: herbie@watdcsu.UUCP (Herb Chong [DCS])
Organization: U of Waterloo
Lines: 82
Summary: 

In article <173@encore.UUCP> goodmon@encore.UUCP (Brian Goodmon) writes:
>What speed does the tape run on the machine that is recording
>the information for a digital master tape?  The reason that I ask is
>that I was wondering if you could put that same info onto a cassette
>tape, and have a D2A/A2D converter at home.  This would allow you to
>reap the benifits of digital reproduction without a CD player, and would
>have the added advantage that you could record digitally yourself.  However,
>some quick figuring seems to suggest that this isn't feasible:  16 bit
>samples at 44.1 K per second means roughly 800 K bits per second;  guessing
>that a cassette tape runs at around 3 inches per second means that the
>information density on the tape would have to be 266 K bits per inch.
>That seems impossibly high, since I seem to remember that computer mag tapes
>have a density on the order of 10 K bits per inch or less.  That makes me
>wonder how fast a digital master tape runs, hence this question.  Have I
>missed something in my calculating?  Also, I guess that another reason that
>this isn't a great idea is that the cassette deck would probably need extra
>functions, like logic to search for beginnings of "tracks", etc.  Oh well.
sharp has made a prototype digital recorder that uses a standard TDK MA-R
cassette (they will use no other) at the same recording speed as a regular
analog cassette.  they use something like 20! channels across the width of
the tape and do strange and wonderful things to bias and equalization
to get something back again.  the system is 14bit logarithmic encoding
at the 44.1kHz sampling rate.  if i remember correctly, sharp stated
that this was a technical excercise to show that it could be done and they
had no plans of any kind to build a version suitable for commercial or
home use.  seems to me that dropouts would be a major problem.

>Are there advantages to a linear tracking tonearm other than the obvious
>removal (you hope) of tracking error?  An article that I copied from Stereo
>Review states that there is no need for anti-skating compensation.  Is this
>true?  Can you explain why?  Their explanation was not clear.  Do they really
>mean "since many linear tonearms are driven by servo motors, the servo motors
>compensate for skating force so that no *additional* compensation is
>necessary"?  What about linear tonearms that don't use servo motors (the
>Souther, for instance)?  Also, what is the audible manifestation of tracking
>error?
antiskating is required in conventional tonearms because of the tonearm
geometry and the resultant forces on the stylus.  the resultant forces
on a tangential turntable happen to be tangential and directly in line
with the tonearm.  thus, no antiskating force is required.  draw yourself
a force diagram of a pivoting tonearm and you can see that there is a net
inward force on the groove which must be compensated for unless you can
live with uneven record wear.

>To the person who asked for headphone suggestions:  listen to Stax.  Their
>electrostatic "earspeakers" are wonderful.  They are also expensive.  Oh
>well.  Even if you can't afford $400, listen just so that you can compare
>other headphones to the best (the best that I've heard anyway).  A cheaper
>brand that has very good sound is Sennheiser (sp?).  They don't have nearly
>the resolution of the Stax, but come in a respectable second.  Unfortunately,
>the only model that I found comfortable to wear (ie. fits around the ear
>instead of pressing against it) is their top-of-the-line.  That translates
>to "most expensive", but it is still cheaper than Stax's bottom-of-the-line.
>Stax also makes electret headphones that beat the Sennheiser sound for only
>slightly more money (around $150 I think).  This model (Lambda Junior it's
>called) might be a good compromise cost/sound-wise.  Electret headphones
>work in much the same way as electrostatics...the difference is that the
>thing that moves to create the sound is a heavier, permanently magnetized
>piece of metal rather than a thin, light, electrically polarized piece of
>saran wrap.
another one to try are the electret headphones by audio technica.  they are
the next best to stax that i have personally heard, and i have listened
to many.  electret headphones do NOT work as described as above.  electro-
static headphones have a metallized mylar film suspended between two plates
that are charged by the external power supply to some 2 to 3 thousand
volts.  the signal is fed to the film and depending upon the polarity of
the signal, is attracted to one plate or the other because of the strong
electric field.  an electret headphone uses a mylar film which has imbedded
charges so that there is a constant electic field around it.  the plates
are fed the signal which has been boosted to the range of about 2 thousand
volts max by the adaptor.  the charged film moves inside this changing electric
field.  that is why both electrostatic and electret headphones required
adaptors or special amplifiers, but the signal is fed to two different places.

Herb Chong...

I'm user-friendly -- I don't byte, I nybble....

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