Newsgroups: comp.sys.amiga.advocacy
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!csn!kessner!david
From: david@kessner.denver.co.us (David Kessner)
Subject: Re: Amiga bashing
Message-ID: <1991Jun26.040339.4568@kessner.denver.co.us>
Organization: Kessner, Inc.
References: <1151@stewart.UUCP> <1991Jun25.153320.26371@bmerh409.bnr.ca> <1991Jun25.164859.12553@mintaka.lcs.mit.edu>
Date: Wed, 26 Jun 91 04:03:39 GMT

In article <1991Jun25.164859.12553@mintaka.lcs.mit.edu> rjc@churchy.gnu.ai.mit.edu (Ray Cromwell) writes:
>  Ok then, how much does it cost and what are it's specs?

Too damn expensive and not good enough.  In that order.

For me to answer that better, first a little history.

Roland came out with the MT-32, a MIDI sound module based on their LA Synth
algorithm.  This is the same method that is used (abit modified) in their D-5,
D-10, D20, D50, D70, and other synths.

For those not familar with MIDI and synthesizers, a 'sound module' (a.k.a.
tone mudule, expander module, etc) is a synthesizer without the piano like 
keyboard.  

The MT-32, now dicontinued, was a good synth in it's day.  It was used in a
large number of professional albums.  Now it can be found used for about $200,
or new (in short supply) for about $350.

Roland realized that there was another market for it-- the home computer user.
It took the MT-32 and combined it with a MPU-401 compatable MIDI interface
and put it on a PC Card.  I don't remember the price, but it was high-- 
somewhere in the $600-800 range.  This card is the LAPC.

At the same time the LAPC came out, Roland released three "Sound Modules'.  One
is a clone of the MT-32, another is like a sampler (but it cannot sample, and
you cannot 'upload' samples to it), and the third is the other two in the same
box.  All of these boast 32 voices (more on that later).  Sorry but I forgot
the model numbers of these boxes.  The problem with these devices is that they
are MIDI, true enough, but they lack the MIDI-implamentation-robustness, and
the front panel LCD based 'user interface' that are very common on other MIDI
Tone Modules. 

That being said...

>The Amiga has cheap, 4 channel DMA 8bit stereo sound. Using DMA
>you get from about 4khz to 28khz sampling rates. (Using
>the processor to write to the DMA data registers directly might provide
>a faster rate, but i've never attempted it.)

Roland does not publish the 'number of bits' in their devices, but it is
commonly accepted that the MT-32 uses 12 bit audio (that's what all the 
pro's say it sounds like).  However, I must mention that the 'number of
bits' and the sample rate of these types of devices matters little, after
all, you cannot send it a digital sample and have it play it so what is the
point?  What does matter is the frequency range and the amount of noise (which
is not always the same as # of bits and sample rate).  With this, I can
say that the MT-32/LAPC sounds ho-hum, but sparkles when compared to the Amiga.
From a professional musican standpoint, the MT-32/LAPC sounds noisy, and the
Amiga is unbareable.

>Audio channels can be
>attached to have one modulate the frequency or amplitude (or both) of
>another channel.

The MT-32/LAPC has 32 voices, as already stated.  But this is not a 'voice' 
in the traditional sense.  Here, a voice can either resemble a subtractive
synth (read: analog synth), or play a small 'sampled sound' (either once, or
repeat it over and over).  A 'PATCH' (what is played when a note is struck), 
is made up of several 'voices'.  

The real power of this not obvious at first (that's why Roland Patented it).
Basically, to make a piano sound, you play a sample of the hammer hitting the
strings while another voice 'synthesizes' the sustaining note.  This provides
an efficent way to reproduce those hard to synthesize parts, while not needing
the power/memory for those killer samples.   This is the basis for Rolands
LA Synthysis.

Now, I never programmed an MT-32, no this part I may be wrong about (I am 
basing this on my D-10, which is very similar).  Each 'patch' can be made up of
up to four voices.  These voices are split into two groups of two.  Each group
is combined using one of several 'algorithms' ranging from mixing them into a 
mono sound, send one left and the other right, and various combinations of
the two with a ring modulator.

(Ok, back to what I know...)  That is what makes up a 'patch'.  Now, each patch
can be panned into one of 16 positions (from left to right).  Now, the number
of notes that can be played at once depends on the number of voices that make
up the patch.  If you use only one voice, then you get 32 notes.  Two will
allow 16 notes, etc.  As a general rule, most sounds use two.  The patches
that use four are quite 'fat' and _usually_ sound muddy when lots of notes are
sounding.  

Eight of these patches can be active at once-- each assigned to a different
MIDI channel.  The output of all of this goes though an effects unit (just
a reverb in the MT-32/LAPC, a reverb/chorus in the D-50 and D-70) and then
you the speakers...

Other than the ring-mudulator, there is no voice to voice modulation-- but it
has not been needed.  Each voice has several envelopes that control pitch, 
low-pass filter, and amplitude while other voice paramaters can be altered by
things like note-velocity, pitch bend, note value, and a low-frequency 
occolator (sp?).  Much more control than the simple voice-to-voice modulation
that the Amiga offers, and it doesnt take up a voice.

>So you can have up to 14bits of information per
>sample (6 bit volume/amplitude modulation on another channel)

Well, no.  It really does not work that way.  Our ears tell us otherwise.


>  The Roland LAPC is well supported how? Can you load up your favorite
>copy of blazemonger and have 16 bit sound? Does the Roland have a 
>DSP on board?

Most IBM games support the MT-32 though an MPU-401 compatable MIDI 
interface.  Since this is the same as an LAPC, it is supported my a lot
of games.  Since it is really MIDI, all sound software worth mentioning
support it.

Yes, it has a DSP, but you might as well ignore it since you cannot program
it.  The entire sound generating section is actually an embedded DSP within
a custom ASIC.  


The Roland LAPC board is a great idea, and it is much more musically useful
than the Amiga's sound.  It even sounds better.  But I believe that it costs
too much for a 'home' device, and it doesn't compare well with other 'pro'
sound modules (even at the same price).  In short, it is great idea but did
not hit the mark.  

Now, I have never actually heard the LAPC (I have used the MT-32 in a concert),
but many, including Roland, say it sounds just like the MT-32 (same patches and
all).  What I really wonder about is the crosstalk.  For instance, if I placed
it into my computer the guts of it would be sandwitched between a disk
controller and a RAM board stocked with eight meg of 80ns, 32-bit RAM.  This
has GOT to create some noise!  (Comments?)

Hope that helps...

-- 
David Kessner - david@kessner.denver.co.us            |
1135 Fairfax, Denver CO  80220  (303) 377-1801 (p.m.) | Reunite PANGEA!
Compuserve?  Isn't that some sort of FIDO BBS?        |