8 Oct
2002
8 Oct
'02
4:23 p.m.
i'd be really suprised if you can get am modulation to work [that's why i
did it with fm]
biggest problem is that amplitude is proportional to rotational speed, and
this gets real ugly when you start moving the record slowly, since the
amplitude changes start to become hard to distinguish from the hand
rumble+surface noise.
as far as sawtooths go...i tried that and found [at least on my shure
m44-7's] that the waveform looks very different when played backwards
[maybe due more to the way that the groove is cut than the way it's
played...but i will note that the backside of a needle quite definitely
has different sonic qualities than the front]
to whomever asked: i'm using a pc104 board [icp wafer 5820] with an extra
soundcard [diamond systems crystal mm-hp]
right now i use ethernet to communicate with a host computer...but i'm
thinking about adding a display so i can just plug an ipod in and use that
to load mp3's.
--
John Ketchpaw
kungfu(a)alumni.cmu.edu
On Tue, 8 Oct 2002, Cornell III, Howard M wrote:
What am I missing here? I don't mean to tell the direction from the time,
but to tell the position from the time. The sawteeth all look the same,
right? Don't we need to tell position somehow?
-----Original Message-----
From: Steve Harris [mailto:S.W.Harris@ecs.soton.ac.uk]
Sent: Tuesday, October 08, 2002 8:59 AM
To: 'linux-audio-dev(a)music.columbia.edu'
Subject: Re: [linux-audio-dev] Final Scratch, custom kernel?
On Tue, Oct 08, 2002 at 07:17:43 -0600, Cornell III, Howard M wrote:
But encode the time so that it can be read
forward or backward.
You dont have to, because you know what direction its being read in from
the saw.
An obvious problem is if you jump, then hold the disk and let it turn
slowly, it might take a fair turn before the position can be read...
45rpm = 1 1/3 sec per rev
assume 2400 baud timcode, 16 bits of timecode info (inc. stop bits etc)
= 13.3ms for 2 whole timecode blocks
therefore (max) 1/100th of a revolution to pick up the timecode position
= 1" at the edge of a 12" record. min would be 1/2"
hmm... that doesn't sound too bad to me, and you may be able to get better
than 16bits @ 2400 baud.
- Steve