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From: ka@world.std.com (Kevin Andresen)
Subject: Re: WHAT IS Roland SCM-55AT and SC-55MKII ???
Message-ID:
Organization: The World Public Access UNIX, Brookline, MA
References: <1995Oct28.160115@acad.drake.edu>
Date: Mon, 30 Oct 1995 16:27:12 GMT
Lines: 99

mcc008@acad.drake.edu writes:



> Can someone explain what SCM-55AT and SC-55MKII are? Are they
>external modules, or how do they compare to SCD-15 and SCCB-1 cards?

> Thanks.......
> Cagri Cakinberk
> mcc008@acad.drake.edu

Yes, I can.
Well actually, the name of the first item is actually SCM-15AT.
It is a combination of the MPU-401AT card and SCB-55 daughterboard.
The SCB-55 daughterboard (commonly referred to by the package name,
SCD-15) is the same in function as the external SC-55mkII module
(with a 16-bit instead of 18-bit digital-to-analog converter (DAC)).

The MPU-401AT is a full intelligent MPU-401 interface board with
a daughterboard (WaveBlaster-type) connector, and headphone &
phono (RCA) line outs.
Most soundcards and Windows-only MPU-401 interfaces use only the
simple ("dumb") UART-mode.
SoundBlaster 16's and AWE32's are fairly unique in that their
MPU-401 UART-mode interfaces are not compatible with industry
standard Windows drivers.
Most older DOS music software and most really old DOS games require
full MPU-401 (most of those old DOS games need an MT-32 anyway
and aren't relevant. A few were for General MIDI Sound Canvas's
but I forget which since they always work on my SCC-1).

The SCC-1B (SCC-1 "B"undled with some software) is a single
card combination of MPU-401 and SC-55 with SC-55mkII instruments.
The SCM-15AT replaces the SCC-1(B).

The SC-55mkII is an external module which is an improvement on
the original Sound Canvas, the SC-55, which has become the standard
of General MIDI. One of them is referred to as the "Gold standard".

(The SC-55mkII added 37 sounds, a couple of minor GS functions,
4 partials ("voices") of polyphony, a serial interface, mixed
analog input, and the 18-bit DAC and vastly improved output section.)

The SC-55mkII has a front panel display and buttons to view
and control most GM&GS parameters.
The SC-55mkII's 18-bit DAC allows more information to be retained
as the samples are mixed (remember, it's done by addition).
It connects by MIDI or serial cable (to PC's and Mac's).
It has an audio in which is very cleanly mixed with the output.

Again the SCD-15(SCB-55) has the same GM/GS sound "engine"
as the SC-55mkII. The samples are identical (I don't know
where the tweaking for the 18-bit DAC is).

I can say that the SC-55mkII is noticeably cleaner than the
U.S. SCC-1(B) (different countries get different versions).
However to notice this, one needs to be at a substantial volume.
Most, if not all, U.S. SCC-1's have a Cutoff Frequency control
which only goes from (-50 to 0) while the SC-55mkII goes from
-50 to +50. That upper half can add a lot to synthy sounds.

The U.S. SCC-1B only has 24 voices (as did the original SC-55).
By "voices", Roland means partials, which reflect the maximum
polyphony (how many notes can be played at once) of the module.
Yamaha uses "voice" to mean what Roland calls "instrument".
Some of Yamaha's voices and Roland's instruments are "patches".
(Ooops, I'm digressing.)

The SCD-15(SCB-55), SC-55mkII, and SCM-15AT have 28.

Current SCC-1B's include all 354 sounds of the mkII but still
use the SC-55 processors.

The SC-50 is identical in quality to the SC-55mkII but is missing
the MT-32 sounds (and a few almost completely unused features).
Since musicians expect the MT-32 sounds on a Sound Canvas, some
GS compositions include them.
My advice: avoid spending so much and ending up short, get the
SC-55mkII.

I've recently hooked up the SC-55mkII to my computer and find
my experience greatly enhanced by being able to easily see
which instruments are playing and what the settings are.

Folks who buy the SC-55mkII can route their SoundBlasters, etc.
through it to avoid the mixer distortion.

To compare in order of sound quality (presence, fullness, and noise).

SC-55mkII
SCD-15(SCB-55) in external box (http://www.holonet.net/pme)
SCM-15AT (no mixer involved)
SCD-15(SCB-55) through a clean host card w/ non-distorting mixer
SCC-1B (older 24-voice processor, SCM-15AT output stage is quieter)
SCD-15(SCB-55) through a typical host card.

Kevin Andresen
ka@world.std.com
MV Prem. 3D, Roland SCC-1(B), SC-55mkII, ...