Digital designs?

The Dark force of dance batzman at gist.net.au
Thu Jan 1 10:53:09 CET 1998


Y-ellow Chad.
        I don't particularly want to go into this with you because it makes
no difference to me what you end up doing. However. You must be running some
nightmare PC or something. I've been doing this shit for 5 years. I have no
problems with noise. Well none worth writing home about. My AWE32 is the
undisputed quietest of the toy cards. Almost as quiet as the Creamware
TripleDAT and certainly a lot quieter than a DAL card D. The GUS is noisy
for several reasons. Bad earthing design and the fact that it uses 13 year
old technology. The DAL card has no excuse. The TBS Maui card is the
noisiest card in the system at the moment. This is straight up transistor
noise from a rather pathetic output stage that TBS still insist on using. It
is slightly more susceptible to noise spikes than any of the other cards but
once again, nothing that can't be dealt with and compared to the noise from
any other given outboard synth, it is not really a problem that can't be
masked. This should not concern you anyway since it is a sample playback
card alone.

It is true that ADICT was designed from the ground up to run Sound cards. 4
at a time as it happens. However it has evolved through a succession of
motherboards from a 486DX-2-66 way back when, through to the 686-166 it is
currently running. There has been no noticeable change in the noise status. 

It is true that coding directly for a PC is not trivial. I never said it
was. However compared to designing proprietary DSP based hardware, then
coding it, the task begins to look far more appealing. Especially for
someone who isn't up on hardware. I reiterate here. We are not talking about
running under Windoze95 in this case. Nor win3.11 or even DOS. We are
talking here about booting the system from ROM and running code directly
from ROM. You may need to add a couple of pieces of addition hardware to
make it behave like an out-board synth such as some Static RAM or EEPROM,
however this is certainly trivial. It could be added into an ISA slot.

A 386 based PC has plenty of power if you know what you are about as a
coder. As long as you are not running microsoft products of course. To give
you an example. A 386 system running Lynux can accommodate up to 16 users.
Running windows it would be slow with only one user. And I know this because
I use to be on just such a system. (Way back when) Obviously running code
directly out of ROM or shaddow RAM would be blindingly fast. You don't need
a hard drive and you may not even need a video card. If you do, it could be
an old Hurc card or even CGA. If you are still worried about noise from the
system, why not isolate the PSU to the sound card or simply put. Use a
linear PSU for the +/-12 volt rails.

Even if you take all these measures on board, it would be simpler than
building a DSP system from scratch. And just before you say. "Put your money
where your mouth is." This is precisely what a friend and I are doing at the
moment. Because of win95's lack of functionality, I need to get the MAUI out
of ADICT and into it's own box. The Maui is only necessary for 'backwards
compatibility' these days so I don't want to spend big bucks on it. So we
are building up a 386 in a 2U 19" rack. Sideways, tree mounted cards. Maui,
Network card and video. No hard drive and we only need the video card so it
will boot. It boots out of ROM, Loads it's OS from the network and runs
remote windowing software so that it is functionally available from ADICT.
Oh did I mention that ADICT also runs a network as standard at the same
time? The new box who's name I haven't decided yet, will be running a very
small switchmode for it's 5 volt rail and a small linear for the +/-12 volt
rails. All the experiments so far have indicated no problems. The hardest
part is stuffing it all into a 19" rack box. Which has to be custom made in
this particular case.

And of course if you want proof that all this stuff works to a professional
level. Go buy my CD. :)

Hope this helps.

Be absolutely Icebox.
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