Re: SoundMeister

[dempson@swell.actrix.gen.nz (David Empson)]

In article <1993May29.144811.27171@nuchat.sccsi.com> glynnet@zero.cypher.com (Glynne Tolar) writes:
> In article <2C06C59C.22851@news.service.uci.edu> andrep@balboa.eng.uci.edu (Andre Prellwitz) writes:
> >
[stuff nuked]
> >
> >Does this mean that the SM somehow bypasses the GS' internal filtering?  I
> >thought the DOC was only capable of outputting ~26K samples/sec (~13KHz
> >effective output) max, but filtered at just below that?  At any rate, unless
> >the SM uses its D/A converters for input monitoring, it makes no sense.
> >
> 
> What filtering?  It connects (like many other sound cards) directly
> to the DOC.  That little 7 pin connector beside it, you know.  The DOC
> cand playback fairly fast.  With this Sonic Blaster it will let you
> sample at 32KHz and playback at 46KHz.  Those are the max settings.

The audio signal on the expansion connector does pass through some
filtering on the the motherboard (lots of RC stuff, and three stages
of an MC34084, on the ROM 03, at least).  The ROM 01 circuitry is
similar up to this point.

> >Oh, btw, how much RAM is on-board?  Will I be able to offload the
> >task of DOC swapping to the SM so I can play MODs in the background
> >while doing file transfers?  And, does it have registers that will
> >allow me to write an output scope as a CDA without having to
> >add/multiply the volume/sample registers on the DOC?  'Twould be neat!
> 
> I am under the impression you've never owned a GS stereo card before.  The
> card has no onboard RAM!

Not true.  The SoundMeister PRO has onboard RAM, which is uses for
fast stereo digitizing.  It is unclear from the descriptions I've seen
as to whether the SoundMeister (non-pro) uses the DOC's D/A converter,
or has its own one.  The Pro version definitely has its own D/A (two
of them). 

In answer to the original poster's question: no.  The RAM on the Pro
version can only be used for digitizing, not for swapping sound into
the DOC.  The card only interfaces with the analog (sound) side of the
DOC - there is no way to intercept the digital side without modifying
the motherboard.

If the card does have any on-board registers, they will only be used
to control the digitizing.

The RAM is used as a digitized data queue, allowing a lot of data to
be digitized at high speed without having to load down the CPU.
Apparently this will be fast enough to digitize in stereo at a high
rate and write the data to the hard drive at the same time.

> It sole job is to get the direct audio from the DOC and make it in
> stereo.  It also features the use of the DOC A/D converter by
> providing simple amplifier and isolation circuitry.  Now the Pro
> version adds its own DOC and has ram for it so as to relieve the GS CPU
> to do other things, like write the data to disk.

More or less correct, but it isn't a "DOC", only a pair of D/A
converters with some attached RAM.
-- 
David Empson                                                               
dempson@swell.actrix.gen.nz                                                
Snail mail: P.O. Box 27-103, Wellington, New Zealand