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Post by JohnG on Jun 17, 2010 6:22:46 GMT
Interesting, a potentially useful site, if it can get them right. The very first connector I checked, MIDI in, was wrong!  Not a good omen.  It shows the incoming screen as being unconnected. If you check with the MMA, the cable has the screen connected. It's only on the equipment itself that the MIDI in should not be connected to chassis earth. Page 2 of the MMA's "MIDI 1.0 Detailed Specification" says "The cable shall be shielded twisted pair, with the shield connected to pin 2 at both ends." Having said that many manufacturers take the MIDI in screen to chassis earth and it becomes necessary to disconnect pin 2 from the cable to avoid earth loops. Important for us lot, eh! JohnG. |
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Post by Sequenzzer on May 29, 2013 12:15:58 GMT
Interesting, a potentially useful site, if it can get them right. The very first connector I checked, MIDI in, was wrong! Not a good omen. It shows the incoming screen as being unconnected. If you check with the MMA, the cable has the screen connected. It's only on the equipment itself that the MIDI in should not be connected to chassis earth. Page 2 of the MMA's "MIDI 1.0 Detailed Specification" says "The cable shall be shielded twisted pair, with the shield connected to pin 2 at both ends." Having said that many manufacturers take the MIDI in screen to chassis earth and it becomes necessary to disconnect pin 2 from the cable to avoid earth loops. Important for us lot, eh! JohnG. I did not know this! With the 6 to 8 midi cables I have connected now,I have been fighting a minor ground loop hum for a long time now and have done everything...cable checks,changing everything out to balanced 1/4 "cables,grounding the rack,etc... Nothing helps to a great deal...Very annoying.. I will try this. Thx,JohnG! |
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Post by frankie on May 29, 2013 13:54:53 GMT
Your hum may be from your PC/laptop.I had same prob when using mains instead of battery.I lifted the earth/ground off laptop power supply.Still off and I am still alive.[about 10 years ago]
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Post by JohnG on May 29, 2013 16:54:50 GMT
I did not know this! With the 6 to 8 midi cables I have connected now,I have been fighting a minor ground loop hum for a long time now and have done everything...cable checks,changing everything out to balanced 1/4 "cables,grounding the rack,etc... Nothing helps to a great deal...Very annoying.. I will try this. Thx,JohnG! My pleasure, It's worth labelling up the cables sometimes, especially if there is an earth loop. The 'out' should have the earth connected and the 'in' may be connected, or not. Whether it is or not depends upon whether the manufacturer of the 'in' equipment has earthed the MIDI connection to ground. According to the MIDI specification it shouldn't be earthed. However, the diagram here: www.midi.org/techspecs/electrispec.php shows in out and thru earthed. Not sure if that's clarified anything? Regards, JohnG. |
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Post by Sequenzzer on May 30, 2013 12:00:27 GMT
Your hum may be from your PC/laptop.I had same prob when using mains instead of battery.I lifted the earth/ground off laptop power supply.Still off and I am still alive.[about 10 years ago] Thx for the suggestion,Frank...Unfortunately,I have a power supply from Dell that only has the two prongs,not the standard 3 pronger with the ground on it. So I can pretty much rule that out...Got some interesting and much needed info from JohnG(Thanks mucho,JohnG!) I'm going to make a special midi cable with pin 2 taken out on the midi in end,since I may have one or more keyboards from manufacturers that may have grounded all their midi ports. I WILL find this evil ground hum monster,and subdue him! Mike |
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