On Sun, 13 Nov 2005 14:48:50 +0000 (UTC), "Nottnick"
wrote:

I need to make my stereo output from a CD player into a mono signal for a PA
amp.

Is it just a matter of joining the 2 grounds together and the 2 signals or
does it need something else?

Help appreciated.

Thanks

Nick

Something else is required.

Tying two stereo outputs together is almost never a good idea - one
can be driving positive while the other is going negative and pull
more current than they were designed for.

You can add a resistor in series to each output and tie both of those
together and use that junction as the input to the PA amp. 1K or so
might be good.

You want to use the "line" output of a portable (if it has one) a
component CD player will be line out as a matter of course. If the CD
player is designed to drive speakers directly the output may need to
be attenuated before it drives a PA amp - or it will overdrive the
input stages and cause distortion.

Grounds are another matter - most portable, and component CD players
use the same ground for both signals - so choose one and route it to
the PA (PA and CD plugged into the same outlet to avoid ground loops).
If you get a lot of hum/buzz there's a grounding problem -

Car CD players frequently use something called amplifier bridging. Two
amplifiers are used to drive the signal and signal return (not really
a ground) out of phase into the speaker - lets them get more watts out
with the power supply restricted to 12 volts. If you connect the
"grounds" together in that case you will burn up one or more
amplifiers.

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