Connecting MOTU 896 to a home receiver with 6ch analog input
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Discussion related to installation, configuration and use of MOTU hardware such as MIDI interfaces, audio interfaces, etc. for Mac OSX
Discussion related to installation, configuration and use of MOTU hardware such as MIDI interfaces, audio interfaces, etc. for Mac OSX
Connecting MOTU 896 to a home receiver with 6ch analog input
Hi, So I purchased a 12ft XLRF to RCA snake to connect the outputs of my 896 to my surround reciever. It works, but I am getting a loud hum noise in the signal. Is there anything I can do to reduce this hum??? I understand that the receiver should be unbalanced, so I set the output scitches on the back of the 896 to -10 and also tried +4, and the same hum was in both. Could it be that the snake needs to be shorter/is wired wrong. Any advice would be great
Hi,
It sounds like a typical "ground loop", where your AC outlet's ground levels from one device to the next aren't at the exact same potential (maybe a difference from each one's path to the main (building's) ground.
IMHO, the first thing to try might be dragging an extension (if necessary) from the receiver's power plug, to wherever your 896 stuff is plugged in, to make sure that's not it.
There are a few different methods for doing balanced to unbalanced, but the ideal way would likely involve transformers (direct boxes):
The usual way, IIRC is to take the hot pin (2) from the XLR (or the tip, if it's balanced TRS) through to the tip or pin on the 1/4" mono or RCA plug on the unbalanced end, and take the shield or sleeve line (pin 1) to the shield (sleeve) on the unbalanced end. Then you'd leave the negative half of the XLR (pin 3 or TRS ring) open.
Then, I've seen the negative and sleeve tied together, and the tip (#2) going it's usual route through and I think, occasionally even the negative hitting the sleeve on the UB end, with the real sleeve only tied to the balanced output side (hanging open at the receiver).
Some of it can also depend on what type of balanced output circuit your first thing is using. You may want to check that snake to see how they've got it wired. I'd guess it's that first way. I know you probably don't want to waste the snake, but if the two devices are on the same power, and you still get the noise, one of the other methods may help. Again, xformers are probably much cleaner if you can scrape together enough of them.
You should be right on the -10 dB setting you used.
If you want to read any on it, Rane's website has always kept a really nice archive of PDF tech documents on audio wiring and i/o circuitry. There are also a couple good books on it: "Audio Systems Design and Installation" by Giddings has more than you'll ever want to know, and Yamaha's ancient "Sound Reinforcement Handbook" is still a good one if you can find it.
If all else fails, use fire.
Good Luck With It,
George
It sounds like a typical "ground loop", where your AC outlet's ground levels from one device to the next aren't at the exact same potential (maybe a difference from each one's path to the main (building's) ground.
IMHO, the first thing to try might be dragging an extension (if necessary) from the receiver's power plug, to wherever your 896 stuff is plugged in, to make sure that's not it.
There are a few different methods for doing balanced to unbalanced, but the ideal way would likely involve transformers (direct boxes):
The usual way, IIRC is to take the hot pin (2) from the XLR (or the tip, if it's balanced TRS) through to the tip or pin on the 1/4" mono or RCA plug on the unbalanced end, and take the shield or sleeve line (pin 1) to the shield (sleeve) on the unbalanced end. Then you'd leave the negative half of the XLR (pin 3 or TRS ring) open.
Then, I've seen the negative and sleeve tied together, and the tip (#2) going it's usual route through and I think, occasionally even the negative hitting the sleeve on the UB end, with the real sleeve only tied to the balanced output side (hanging open at the receiver).
Some of it can also depend on what type of balanced output circuit your first thing is using. You may want to check that snake to see how they've got it wired. I'd guess it's that first way. I know you probably don't want to waste the snake, but if the two devices are on the same power, and you still get the noise, one of the other methods may help. Again, xformers are probably much cleaner if you can scrape together enough of them.
You should be right on the -10 dB setting you used.
If you want to read any on it, Rane's website has always kept a really nice archive of PDF tech documents on audio wiring and i/o circuitry. There are also a couple good books on it: "Audio Systems Design and Installation" by Giddings has more than you'll ever want to know, and Yamaha's ancient "Sound Reinforcement Handbook" is still a good one if you can find it.
If all else fails, use fire.
Good Luck With It,
George