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Geregistreerd: 21 nov 2011 12:00
Woonplaats: Ermelo
05 jan 2015 18:15
Midi kabel (met schema)
Laten we het nou een beetje goed houden allemaal......Prima die aanvulling, maar helaas is een Midi kabel geen audio kabel, ook al wordt het er vaak voor gebruikt.
Dit heeft te maken met het voorkomen van ground-loops. Daartoe zijn in het Midi protocol een aantal maatregelen genomen. Zodanig, dat de aarde van apparaat 1 nooit kontakt kan maken met de aarde van apparaat 2.
En daar zondigen sommige kabels nog wel eens tegen. Zie schema een kommentaar....
Pin 2 of the MIDI OUT connector should be grounded. That way the shield of the MIDI cable will be grounded on one end as desired.
Ground loops will cause horrendous hum, buzzes, and other noises, especially when connected to computerized gear or lighting equipment. The noises are caused by differences in voltage potential from one end of the cable to the other. The remedy, of course, is to run balanced audio lines and to NEVER physically connect the chassis grounds of different pieces of equipment together. MIDI instrument designers understand ground loops. In fact, a major design goal of MIDI, as seen in the electrical specification explanation in the MIDI Specification Document, is to prevent any ground loops that might occur with the MIDI cables. This is done by using a balanced current loop through an opto-isolator and only grounding the MIDI outputs. The MIDI IN connector is not grounded to the receiver's chassis. When done correctly, there are no ground loops and no hum or other noises caused by the MIDI setup.
Designers of personal computers are not generally audio engineers and apparently have not heard of ground loops. In fact, given the noisy fans and screaming disk drives that go into the PC, it is a wonder they can hear at all. All that noise forces some audio professionals keep the computer in a closet or another room. But the primary source of ground loop problems in PC audio is the PC soundcard MIDI interface.
A PC soundcard exports the serial MIDI signal from its UART on two pins of its joystick or game port. A $50 cable converts this to the approved MIDI connector, and is supposed to include the necessary opto-isolator for conversion to the required balanced current loop. The MIDI IN connector is supposed to have the opto-isolator and no ground connection to pin 2 or to the shield for the express purpose of avoiding a ground loop.
We were able to locate six different such cables, all of which violate the MIDI hardware specification by grounding both MIDI connectors (MIDI IN and MIDI OUT). ALL of these cables will cause ground loops, and generate hum and other unnecessary noise.
Dit heeft te maken met het voorkomen van ground-loops. Daartoe zijn in het Midi protocol een aantal maatregelen genomen. Zodanig, dat de aarde van apparaat 1 nooit kontakt kan maken met de aarde van apparaat 2.
En daar zondigen sommige kabels nog wel eens tegen. Zie schema een kommentaar....
Pin 2 of the MIDI OUT connector should be grounded. That way the shield of the MIDI cable will be grounded on one end as desired.
Ground loops will cause horrendous hum, buzzes, and other noises, especially when connected to computerized gear or lighting equipment. The noises are caused by differences in voltage potential from one end of the cable to the other. The remedy, of course, is to run balanced audio lines and to NEVER physically connect the chassis grounds of different pieces of equipment together. MIDI instrument designers understand ground loops. In fact, a major design goal of MIDI, as seen in the electrical specification explanation in the MIDI Specification Document, is to prevent any ground loops that might occur with the MIDI cables. This is done by using a balanced current loop through an opto-isolator and only grounding the MIDI outputs. The MIDI IN connector is not grounded to the receiver's chassis. When done correctly, there are no ground loops and no hum or other noises caused by the MIDI setup.
Designers of personal computers are not generally audio engineers and apparently have not heard of ground loops. In fact, given the noisy fans and screaming disk drives that go into the PC, it is a wonder they can hear at all. All that noise forces some audio professionals keep the computer in a closet or another room. But the primary source of ground loop problems in PC audio is the PC soundcard MIDI interface.
A PC soundcard exports the serial MIDI signal from its UART on two pins of its joystick or game port. A $50 cable converts this to the approved MIDI connector, and is supposed to include the necessary opto-isolator for conversion to the required balanced current loop. The MIDI IN connector is supposed to have the opto-isolator and no ground connection to pin 2 or to the shield for the express purpose of avoiding a ground loop.
We were able to locate six different such cables, all of which violate the MIDI hardware specification by grounding both MIDI connectors (MIDI IN and MIDI OUT). ALL of these cables will cause ground loops, and generate hum and other unnecessary noise.
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