issue06

EMUSIC-L Digest                                      Volume 46, Issue 06

This issue's topics:
	
	LAPC etc.
	LAPC-1 MCB-1 (10 messages)

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Date:         Mon, 9 Nov 1992 15:46:35 CST
From:         GE2516@SIUCVMB.SIU.EDU
Subject:      LAPC etc.

I'm no expert, but I believe the LAPC is an MT32 on a PC card with an MPU401
interface.  I'm sorry I can't help any further--anyone else have any ideas?


    Eric Nielsen                              GE2516@siucvmb.siu.edu
University Electronic                      Southern Illinois University
   Communications                                 at Carbondale

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Date:         Mon, 2 Nov 1992 09:05:15 CST
From:         "(Michael Colicos)" 
Subject:      LAPC-1 MCB-1

Does anyone know the pin assignments for the d_sub connector on the LAPC-1?
As a guitarist I never got the DCB-1 midi connector box, but I now want to
connect an old midi keyboard that I just picked up.  Having to now pay
another $100+ for an 'adaptor' stinks of a marketing move to me, so I want
to try and wire my own.  Thanks.

Michael Colicos
mcolicos@nba19.med.uth.tmc.edu

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Date:         Mon, 9 Nov 1992 13:59:39 EST
From:         ronin 
Subject:      Re: LAPC-1 MCB-1

i don't know what the LAPC-1 is, but if the DCB connector that
you refer to is part of Roland's old communication standard, you can
forget just wiring a midi-dcb interface yourself. midi is a serial
data communications standard entirely distinct from the parallel mechanism
developed by roland for its dcb system. you'd need to capture, translate,
and re-emit the data, requiring at least a small microprogrammed processor.

-----------< Cognitive Dissonance is a 20th Century Art Form >-----------
Eric Harnden (Ronin)
 or 
The American University Physics Dept.
4400 Mass. Ave. NW, Washington, DC, 20016-8058
(202) 885-2748
---------------------< Join the Cognitive Dissidents >-------------------

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Date:         Tue, 10 Nov 1992 13:07:00 +0800
From:         H8710244@HKUCC.HKU.HK
Subject:      Re: LAPC-1 MCB-1

e is no processor inside. I am B. Sc. in Electronic Engineering.
I am confident of it.

from,
Roland
h8710244@hkucc.hku.hk

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Date:         Tue, 10 Nov 1992 07:50:45 CST
From:         "(Michael Colicos)" 
Subject:      LAPC-1 MCB-1

The LAPC-1 is advertized as a MT32 and a MPU401 on a card.  I bought one
figuring it was cheaper than getting the two units separately.  I didn't
have an immediate use for the MPU401, so when I read in the "manual" that
I would need an extra connector, the MCB-1 to use the MPU401, I didn't buy
one and figured it was an inexpensive adaptor of some sort.  After picking
up an old midi keyboard, I checked the price and it's $150 from Roland!
As you can buy an MPU401 cheaper than that, I was quite dismayed, and sent
the original message out about wiring it yourself.
Since then this is what I've learned.  Of the 5 MIDI pins, 2 and 4 (going
clockwise) carry the serial MIDI data, and 3 connects to the shield.  The
LAPC-1 has a DB-15 joystick style connector.  An hour of experimentation
found the following

      2 - X
            X
          X
            X
          X
            X
          X
            X
          X
            X
          X
            X - 4
          X
            X
          X

This results in a fully functional link between my keyboard and the MPU401.
I am sure this is not blessed by Roland, and I have no idea whether or not
it can harm the LAPC-1, but it does work.  And it beats dropping another $150.

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Date:         Tue, 10 Nov 1992 08:01:04 CST
From:         "(Michael Colicos)" 
Subject:      Re: LAPC-1 MCB-1

Yes, I believe the IC's you get are for ..... the metranome!

------------------------------
Date:         Tue, 10 Nov 1992 22:06:00 +0800
From:         H8710244@HKUCC.HKU.HK
Subject:      Re: LAPC-1 MCB-1

Do you mean that you just connect the cables and no electronic component?

------------------------------
Date:         Tue, 10 Nov 1992 08:16:42 CST
From:         "(Michael Colicos)" 
Subject:      Re: LAPC-1 MCB-1

Well, since my keyboard sits 4 feet from my computI guess thats why I have
no problems.  I have no plans to go on the road with this equipment, so I'll
stick to my cheap setup.

------------------------------
Date:         Tue, 10 Nov 1992 22:17:00 +0800
From:         H8710244@HKUCC.HKU.HK
Subject:      Re: LAPC-1 MCB-1

No, the IC is not for metranome.

------------------------------
Date:         Tue, 10 Nov 1992 22:18:00 +0800
From:         H8710244@HKUCC.HKU.HK
Subject:      Re: LAPC-1 MCB-1

One IC is used for strengthen the signal and one to prevent shortage if the
computer and the MIDI device have got different grounds.

------------------------------
Date:         Thu, 12 Nov 1992 11:33:02 MET
From:         cgra@BTMA74.DNET
Subject:      RE: LAPC-1 MCB-1

You should really have an opto-isolator on the circuit somewhere:
                 +--------+
    ----->-------+-+    +-+----->---
       300 mA(?) ! ! -> ! !
    ------<------+-+    +-+-----<---
                 +--------+
                opto-isolator

The o-i serves both to prevent the whole midi rig from becoming a huge aerial
to pick up all the electical noise in the joint, and to electically isolate the
various instruments from eachother, reducing the incidence of "fried musician
syndrome". Probably neither really counts in your case, but it's worth knowing.

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