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I need a mixer for a 3-mic PA system
I’m installing a sound system for a church and they’ve asked for a 3-microphone setup. I’ll be powering 6 Martin Logan Vignette speakers through a Denon AVR2808CI A/V receiver. I need a mixer that can take 3 Crown CM200A cardioid condenser hand-held mics. They’ll plug into 3 mic wall jacks wired into a mixer with a variable, unbalanced line out so I can set the output level so as not to over-power the Denon amp & speakers.
Can balanced mics be converted to unbalanced so it all works well in an A/V system? Do I need a ‘pre-amplified’ mixer like the Crown 14M? Or one that’s not pre-amped?
Senior System Designer
Magnolia Audio Video
Reply: A four-channel mic mixer with phantom power will work. The Crown 14M is an example.
Here’s a link to its data sheet: http://www.crownaudio.com/pdf/ca/138119.pdf
A mic mixer is the same as a preamplifier-mixer. It has several mic preamps built in, one for each channel. Balanced mics plug into a mixer with balanced mic inputs. Those input connectors go to mic preamps in the mixer (like the 14M). The amplified mic signals are mixed together into a single mono line-level signal that exits the mixer. You can vary the mixer output level by adjusting the master gain pot. If the line-level output signal is balanced, you can unbalance it as described below. Plug the unbalanced cable into the Denon receiver aux input.
The 14M line output connector is balanced, but you can unbalance it:
1. Take the unbalanced cable that will go from the mixer to the Denon receiver. Strip the end of the cable nearest the mixer.
2. Connect the cable hot lead to line output connector pin 2.
3. Connect the cable shield to pin 1. As an option, also connect pin 3 to shield.
You might consider using an automatic or gated mixer, which turns off mics that are not in use, resulting in a clearer sound with less feedback. The 14M is not gated but it might be perfectly adequate. Here’s a link to the Audio-Technica MX341a automatic mixer with 4 mic inputs:
Here is a link to the CM-200A microphone data sheet:
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