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Old 2nd October 2012, 04:53 AM   #1
whtwter is offline whtwter  United States
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Default Stereo RCA- mono phoenix on amp? Help!

I have to wire a RCA stereo signal to a mono amp through a phoenix connector. Not by choice but I received the wrong equipment and have to make it work at least for a couple days. The amp has a positive negative in on the phoenix connector. I tried tying the soldering the RCA's together on one end red and white together and neutral together and connecting that to the phoenix connector on the + -. It worked but got a lot of pop and crackle when the volume is higher. I am thinking since I only have 2 wires per channel if I leave the red and white separate and connect them to the + - tie the neutrals and connect to neutral on the phoenix it might work. Am I on the right track?

Thanks!
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Old 2nd October 2012, 11:27 AM   #2
sreten is offline sreten  United Kingdom
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Hi,

Never directly tie two stereo outputs together to go into a mono input.

At minimum you need a series resistor in each channel before joining them.

rgds, sreten.
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Old 2nd October 2012, 11:36 PM   #3
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I haven't come across "phoenix connectors" before but I assume you are describing a mono, balanced line input to the amplifier and you have a stereo pair of RCA leads to connect and feed in. Using a couple of 10k resistors, join them one end and that is the output +. Connect the other ends to each RCA lead centre and join the shield connections together - that is the ground or shield connection. This is sometimes called a "Y adaptor" and is as Sreten also suggests.

The problem is that a balanced connection requires an unbalanced: balanced line transformer or an active circuit to adapt this and change the characteristic impedance from 47k at the RCA lead to 600R across the +/- balanced line terminals. This thread and others discuss the problem, if I have got your situation right....
Line input transformer for unbalanced to balanced conversion

To do it properly will cost $$ and require a complex device in any event - not something that can be knocked together in 5 minutes with junkbox bits but I have seen a lot of guys try, only to come up with hum, noise, low bandwidth and low input to the amp. Still, as a desperate measure, someone might have a workaround that gets you out of trouble.
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Last edited by Ian Finch; 2nd October 2012 at 11:42 PM.
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Old 3rd October 2012, 06:53 AM   #4
whtwter is offline whtwter  United States
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Thank you! Looks like we will be changing the amps out and adding a mixer but the info provided got things running for the event today and though it wasn't a permanent solution it worked well at the volume needed. You gave me the info needed to push to get the right equipment. I am still learning and happy to have a job that I don't mind doing research for on my own time and happy to have a resource that makes me look good. Had to do a bit of reading based on the responses but gained a lot today!

Cheers
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