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From: grr@cbmvax.UUCP
Newsgroups: comp.sys.mac,comp.sys.amiga,rec.audio,rec.music.synth
Subject: Re: Mac II D/A resolution
Message-ID: <1640@cbmvax.cbmvax.cbm.UUCP>
Date: Tue, 7-Apr-87 01:10:13 EST
Article-I.D.: cbmvax.1640
Posted: Tue Apr  7 01:10:13 1987
Date-Received: Fri, 10-Apr-87 00:31:58 EST
References: <585@plx.UUCP>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 35
Keywords: 16-bit?
Xref: utgpu comp.sys.mac:2202 comp.sys.amiga:3304 rec.audio:1101 rec.music.synth:572

In article <585@plx.UUCP> ed@plx.UUCP (Ed Chaban) writes:
>I've heard conflicting reports about the MacII's D/A resolution.
>Would anyone at Apple care to set me straight?
>
>How can you say the Mac II  delivers CD audio quality with only 
>8-bits of resolution?  Exponential D/A converters A'la Amiga?
>I  hope not...
>
>-ed-

Ed, old buddy, the Amiga D/A's are 8-bit *linear* with a 6-bit volume
control.  You can view this as floating point if you wish, but it's
quite different from the exponential converters used on some "noise
generator" class chips.

The Mac II can manage a 44KHz sample rate, but it can't handle the
14-16 bits normally considered as CD quality.

The Amiga is nominally limited 8 bits, with a 28.8 KHz, but by playing
games with the multiple channels and volume controls you can get another
bit or two and get some rather impressive dynamic range.  If you are
willing to dedicate the processor to sound generation you can directly
drive the sound channels to achieve >> 44KHz sampling rates.  (a little
snip-snip on the low-pass filter helps here).

Still, 16-bit resolution at 44KHz would be nice, but one has to comtemplate
the noise floor in the personal computer environment, especially when using
on-chip converters.

I haven't seen/heard the Mac-II yet, but I have seen Bob Hoover demonstrating
his Mimetics/Soundscape stuff.  Pretty nice...
-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)