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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

2105.0. "Amiga Causing Noise When MIDI Cables Connected" by GVA05::BERGMANS () Tue Aug 29 1989 12:36

    I have made the step to MIDI. I am using Dr T sequencer software
    running on an AMIGA through a serial---->MIDI converter.
    
    At this point it is only connected to a DX7 II.
    
    I use ROLAND MIDI cables to connect the stuff.
    
    Here is the problem.....NOISE..,not only some hum, but as soon
    as the MIDI cables are connected between the AMIGA and the DX7 II
    I can hear soms of the typical computer (electronic) noises through
    the amplifier.
    
    It includes different frequencies, for example some a very typical
    when the disk drive seeks.
    
    Some noise disappears when I power off the AMIGA screen.
                          
    I this usual or is there something wrong with my set up.
    
    Reagrds
T.RTitleUserPersonal
Name		DateLines
2105.1try everything and anythingANT::JANZENcf. ANT::CIRCUITS,ANT::UWAVESTue Aug 29 1989 13:1014
    Welcome to the electronic age.
    Certainly swithcing in the disk drive is probably in the audio
    range.
    It may be coupling as radiated interference at the amplifier.
    How are you monitoring the sound?  Use short shielded cables of
    all types, but especially of the audio line cables from the dx to
    to an amp.   verify that your midi cable setup is as short as possible
    and uses real shielded midi cables.
    On the other hand, you could try moving the dx farther from the
    computer and use a longer MIDI cable, if it is radiated interference.
    Some EMI may couple as conducted through cables and the power lines.
    Try plugging the dx and amp into a different ac power outlet, although
    this could cause hum.
    Tom
2105.2on the ground pins and ground screwsANT::JANZENcf. ANT::CIRCUITS,ANT::UWAVESTue Aug 29 1989 13:114
    Also try grounding all the equipment together with thick copper
    wire in a grounding tree to earth ground (don't accidentally
    electrocuteyourself)
    tom
2105.3re-read noteANT::JANZENcf. ANT::CIRCUITS,ANT::UWAVESTue Aug 29 1989 13:134
    I read your note again.  I get the impression that the noise is
    conducted EMI, and goes through the MIDI cable.  Try grounding the
    boxes together.
    Tom
2105.4The Noise of Computing?DRUMS::FEHSKENSTue Aug 29 1989 13:2812
    The Amiga 1000 CPU box generates a fair amount of RF EMI.  When my Amiga's
    computing furiously while the monitor's switched to the video input
    (sourced by my VCR), there's considerable interference on channels
    2 through 5.  (Right now it's running a Griffeath Cellular Automaton
    on a 360 * 312 cell space, which takes about 20 minutes per iteration,
    and was started late last Friday night - it should have stabilized
    in the "demon" phase by the time I get home tonight... see last
    month's Scientific American's Computing Recreations).
    
    len.
2105.5probably audio, not MIDI.DYO780::SCHAFERBrad - boycott hell.Tue Aug 29 1989 15:5313
    I'd be suspect of your audio cables and amp before I'd worry about MIDI
    connections.  Make sure your audio cables are in good shape and are
    shielded - and make sure they're a LONG way away from the monitor. Same
    goes for your amp and speaker wires. 

    If the Amiga and monitor are anything like the AtariST & monitor, there
    will be a substantial amount of RF. 

    Although I suspect that the MIDI connection is a symptom rather than a
    source, you'd do well to follow Tom's advice as well - make sure your
    MIDI interface is connected/grounded properly. 

-b