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Conference napalm::commusic_v1

Title:* * Computer Music, MIDI, and Related Topics * *
Notice:Conference has been write-locked. Use new version.
Moderator:DYPSS1::SCHAFER
Created:Thu Feb 20 1986
Last Modified:Mon Aug 29 1994
Last Successful Update:Fri Jun 06 1997
Number of topics:2852
Total number of notes:33157

2541.0. "Midi filter?" by DNEAST::BOTTOM_DAVID (victim of unix...) Thu Jan 10 1991 16:21

I'm finding myself as an apprentice midi rack puke in a bit of a quandry.

I'm switching my guitar preamp with a midi patchbay, and my quadraverb 
also. However the quad re-starts it's processing algorhythm even 
if I select the same patch. The stupid but payed for and rather inexpensive
patch bay runs in omni mode...I need a router, filter or whatever to
keep the patch bay from seeing messages on one channel (intended for the
quad) so I can switch the preamp without switching the quad and vice
versa...

whatever I get needs to be small and cheap and only needs to support 
2 end devices...

does anatek or one of those other companies make a small cheap widget to 
do this?

thanks

dbii
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2541.1DCSVAX::COTEEdd,11 - Mousies, 12Thu Jan 10 1991 16:246
    > Does anatek...?
    
    They make a whosis called the pocket filter, but I'm not sure if
    it will filter "all but channel X" messages.
    
    Edd
2541.2Anatek makes "Pocket" anything...TLE::TLET8::ASHFORTHThe Lord is my lightThu Jan 10 1991 16:3015
Yep, Anatek's the place, Pocket Filter is the gadget. I haven't seen anything
they make that isn't $99.95, so I'm pretty sure that's the retail.

You didn't mention the brand/model of your "stupid patch bay;" would you? I'm
eventually going to be in the market for a less-than-genius-level but
not-too-stupid patch bay, and I'm more than willing to learn from your
experience (nice, ain't I?).

BTW, does yours have MIDI merge?

(Does anyone mind if I turn this into a MIDI patch bay note? Thanks, I thought
not.)

Cheers,
	Bob
2541.3In the PocketAQUA::ROSTDickie Peterson WannabeThu Jan 10 1991 16:523
    To "de-omni" you need the Pocket Channel which is a channelizer.
    
    							Brian
2541.4Does anyone ever use OMNI???DCSVAX::COTEEdd,11 - Mousies, 12Thu Jan 10 1991 16:555
    I think you may have to possibly rearrange your rack topology so that
    the OMNI device is either at the end of the chain, or on it's own leg
    from a thru-box...
    
    Edd
2541.5I'm zero for two when it comes to MIDI merge devices!DREGS::BLICKSTEINI'm hungry, I'd like 2 all-u-can-eat plattersThu Jan 10 1991 20:004
    I've had problems with my Anatek Pocket Merge.  Somehow, it manages to
    introduce noise into the audio lines.  From what I know of MIDI it
    should not be possible (MIDI ground is isolated) but it does seem like
    line induced noise of some kind.
2541.6 ANATEK POCKET STUFFCITYFS::DARRENNot now, I'm eating my lunch!!! Thu Jan 10 1991 20:1917
    
    
         I was worried about how the Anatek devices would affect devices	
    due to the fact that they draw power from gnd ( pin 1 ) of the midi out.
    
       Anatek pocket boxes dont work on some devices that dont have pin 1 of 
    the midi out/thru port grounded. Try running a midi cable without pin 1
    connected from the midi out of the Pocket merge and only have one of
    the input cables grounded because it sounds like the two devices
    getting merged are in a ground loop.
    
         I'm just about to buy the pocket merge so let me known how you go.
    
    
    BC
    
     
2541.7there ARE cheaper ways to cause grounding probsKEYS::MOELLERStressed ? Just say 'Damitol'-I do!Thu Jan 10 1991 20:4316
    <<< Note 2541.6 by CITYFS::DARREN "Not now, I'm eating my lunch!!! " >>>
>       Anatek pocket boxes dont work on some devices that dont have pin 1 of 
>    the midi out/thru port grounded. Try running a midi cable without pin 1
>    connected from the midi out of the Pocket merge and only have one of
>    the input cables grounded 
    
    How would one do this ?  Pull out pin 1 with needlenosed pliers ?  All
    the MIDI cables I have are molded.  And I thought that the reason for
    the opto-isolators in the MIDI spec is to prevent any grounding or
    electrical differential stuff !  It's either isolated or it's not.
    Clarification ?
    
    >because it sounds like the two devices getting merged are in a ground loop.
    
    karl, owner of a Pocket Merge, the first connection of which caused my
    KX88 to LOSE ITS MIND (see another note)
2541.8one more time: this is your brain with a groundloopAQUA::GRUNDMANNBill DTN 297-7531Fri Jan 11 1991 10:5831
    I'm familiar with the MIDI Specification, and the way it's supposed
    work: Sender grounds the shield, receiver does not touch the shield.
    Sender drives current through the pair of MIDI signal wires, receiver
    uses that current in an optoisolator. They show a sample circuit with a
    driver IC and a 220 ohm resistor in series, and they call out an
    optoisolator. At the bottom of the schematic, part numbers are called
    out with "or equivalent"... that's what I call a spec!
    
    Using the shield to derive power is risky at best. The schematic
    implies a clear relationship between the signal wires and the ground,
    but I would think that as long a product drives the proper current
    through the signal wires, it wouldn't matter if the voltage
    differential  of the signal wires to ground were 0 volts, or 5 volts,
    or whatever (120 VAC? :-)
    
    Some products may be very sensitive to having current drawn out of the
    current loop for the MIDI signal through the ground. I guess Karl has
    one of those. I wouldn't be surprised to hear someone report that their
    equipment was DAMAGED by device that uses the ground path.
    
    On the other hand, it really doesn't say anywhere what to do with boxes
    that don't have their own grounds. Maybe passing the ground through the
    box makes sense. But what about something like a pocket merge: it
    receives two inputs, which one should be used for ground? Using both
    would cause a ground loop, using just one means it may be noise
    sensitive when only one input is used (the ungrounded one). Maybe
    letting the ground float makes sense? The spec doesn't say...
    
    The really "correct" way to do this would be for every MIDI device to
    have its own power supply. A "pocket" midi box with a battery doesn't
    seem too bad. How 'bout another wall bug?
2541.9They work fine in my set upCSC32::MOLLERThis is a computer isn't it? Why not?Fri Jan 11 1991 16:4219
	I have 2 of the pocket merges & have not had any problems (these
	are attached to an ESQ-1, MDF-1 Disk Drive, and U-110 in my second
	rack (the MDF-1 is a backup incase my other disk drive dies).

	I did notice, however, that the pocket merge can derive power from
	one of the MIDI IN's and the MIDI OUT, which implies that you could
	get some surprize grounds that you weren't expecting. It also
	allows you to pass the power ground down the chain if you have 2
	mergers (like I do). I'm positive that the short info sheet that comes
	with the merger shows this.

	Both of mine work substantially better than the Yamaha YMM merger
	box I have (the Anateks pass SYSEX without overflows).

								Jens

	(by the way, I use a merger in my MX-8, and an MM1 plus the 2
	Anatek Midi-Mergers in my 2 racks - I allow any of 4 controllers
	to access just about anything in both racks).
2541.10DNEAST::BOTTOM_DAVIDvictim of unix...Mon Jan 14 1991 13:4420
Well my patch bay is a kitty hawk (see guitar notes for extensive blah blah
blah about kitty hawk)

it features: an audio a/b loop 
	     1 momentary contact switch
	     6 open/ground switches

everything is relay driven. The bay is designed to allow you to replace
footswitches etc. that a guitar player with lots of toys might have to deal 
with...

I found a pseudo-workaround thanks to the extensive amount of features in
my foot controller. It's convoluted but it works...thankfully I have no 
need for additional hardware.

As near as I can tell all midi signal processors will flush the audio pipe
and restart the current program even if you select the same one again, 
causing an audible glitch.

dbii