AES digital audio connections.
I am working with a church on changes to their sound system. One of the projects is they want the mix position moved and shrunk. At the moment the system has 4 Rane RPM26z DSPs for the house speakers. They are in a rack at the mix position. I am thinking of moving them to the amp room. They are presently wired with what I would call a reverse telescoping ground. It is lifted at the DSP and connected at the amp. I was told there were problems with these units when it was grounded on both ends of the signal cable. Yesterday when doing some work there I had part of the mix booth systems on but I forgot to turn on the DSPs. When I turned on the amps there was a bad hum/buzz in the system. When I turned on the DSPs the noise went away. I am thinking that this is showing a fault with the present wiring. IN other words it could be better.
As part of the changes the plan is to install a digital mixer that has AES outputs. I am thinking it would be better to have the DSPs in the amp room with relatively short (analog) cable runs from the DSPs to the amps. I would like to take the shortest path (may be about 120 feet) from the mixer to the DSPs but I am told that where the wires are now run under floor (yes there is a finished basement) may be difficult due to changes in the basement over the years. I need to get in and remove a bunch of ceiling tiles and see for myself. The longer path would be over the top and probably be about 220 feet. We are also doing a bunch of lighting upgrades that will involve running DMX cable. Any cable that I run will be the plenum type of cable. We will be using the 2 pair version of DMX cable. The spec on the DMX cable I have is 100 ohms nominal. The Rane DSPs specs call for a maximum cable length of 100 meter so either path is under the maximum. But there is no spec that tells you what the impedance on the AES input is for the Ranes or what it expects the cabling to be. When I spoke to the wire specialist at West Penn Wire he said that in the 110ohm spec for AES and the 120ohm spec for DMX there is a plus and minus 10 percent leeway. So it actually sounds like the impedance of the DMX cable I have (part number found under spec for DMX cable on West Penns web site) is more of a match for AES then DMX.
So the question I have is does any one have experience using DMX cable for AES runs and ignoring the second pair? I had to buy 2 1000 foot rolls of DMX cable to get enough for the lighting runs and I will most likely have enough left over to do the AES runs.
I am working with a church on changes to their sound system. One of the projects is they want the mix position moved and shrunk. At the moment the system has 4 Rane RPM26z DSPs for the house speakers. They are in a rack at the mix position. I am thinking of moving them to the amp room. They are presently wired with what I would call a reverse telescoping ground. It is lifted at the DSP and connected at the amp. I was told there were problems with these units when it was grounded on both ends of the signal cable. Yesterday when doing some work there I had part of the mix booth systems on but I forgot to turn on the DSPs. When I turned on the amps there was a bad hum/buzz in the system. When I turned on the DSPs the noise went away. I am thinking that this is showing a fault with the present wiring. IN other words it could be better.
As part of the changes the plan is to install a digital mixer that has AES outputs. I am thinking it would be better to have the DSPs in the amp room with relatively short (analog) cable runs from the DSPs to the amps. I would like to take the shortest path (may be about 120 feet) from the mixer to the DSPs but I am told that where the wires are now run under floor (yes there is a finished basement) may be difficult due to changes in the basement over the years. I need to get in and remove a bunch of ceiling tiles and see for myself. The longer path would be over the top and probably be about 220 feet. We are also doing a bunch of lighting upgrades that will involve running DMX cable. Any cable that I run will be the plenum type of cable. We will be using the 2 pair version of DMX cable. The spec on the DMX cable I have is 100 ohms nominal. The Rane DSPs specs call for a maximum cable length of 100 meter so either path is under the maximum. But there is no spec that tells you what the impedance on the AES input is for the Ranes or what it expects the cabling to be. When I spoke to the wire specialist at West Penn Wire he said that in the 110ohm spec for AES and the 120ohm spec for DMX there is a plus and minus 10 percent leeway. So it actually sounds like the impedance of the DMX cable I have (part number found under spec for DMX cable on West Penns web site) is more of a match for AES then DMX.
So the question I have is does any one have experience using DMX cable for AES runs and ignoring the second pair? I had to buy 2 1000 foot rolls of DMX cable to get enough for the lighting runs and I will most likely have enough left over to do the AES runs.
