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

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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"default" wrote in message
...
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.

+++++++++++++Is there any chance you could explain this in a bit more detail
please.

+++++++++++++What do you mean by tie together - sorry, I'm good at soldering
etc.

+++++++++++++ I can follow instructions / diagrams but just don't know the
theory.




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.

+++++++++++++++ That's fine - it is a line output on a Denom component
player.



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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Thanks a lot for this advice.

Nick

On Sun, 13 Nov 2005 17:17:26 +0000 (UTC), "Nottnick"
wrote:


"default" wrote in message
.. .
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.

+++++++++++++Is there any chance you could explain this in a bit more detail
please.

Take the output of the CD player right channel signal and connect a
small 1,000 ohm resistor to it. Do the same to the right channel.
Connect (tie) the free ends of both resistors together and to the PA
amp mono input. (a total of three connections soldered together - one
is a wire that goes to the PA input).

Run one ground wire to the PA from one of the CD outputs. You may
also run two ground wires from each CD output, but it shouldn't be
necessary.

This should be done with shielded (coaxial) cable, but may work fine
with ordinary hook up wire if the wires aren't too long. The
potential for noise and hum pickup is dependent on a few variables so
try it one way and see what happens.



+++++++++++++What do you mean by tie together - sorry, I'm good at soldering
etc.

+++++++++++++ I can follow instructions / diagrams but just don't know the
theory.




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.

+++++++++++++++ That's fine - it is a line output on a Denom component
player.

Then the signal level should be fine for the PA input unless it is a
microphone input - If you have a choice on the PA use the line input
(line out (CD) to line in (PA))

Line levels are usually around one volt to drive the PA to full output
(it will be in the PA specifications under the term "input
sensitivity" or some such description)

Microphone input on a PA amp can be much less - in the millivolt
range. PA amps usually have both types and a front panel switch to
select the source(s).

Your grounding shouldn't be a problem unless you need to run them on
different power receptacles then you may get hum. If that's the case,
post again.


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 -


Regards
bob
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On Sun, 13 Nov 2005 23:31:41 -0500, default wrote:

Do the same to the right channel.

Change that to "Do the same to the left channel."
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You are a real star, thanks so much for your help

Nick

"default" wrote in message
...
On Sun, 13 Nov 2005 23:31:41 -0500, default wrote:

Do the same to the right channel.

Change that to "Do the same to the left channel."
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"Nottnick" wrote in message
...
You are a real star, thanks so much for your help

Nick

"default" wrote in message
...
On Sun, 13 Nov 2005 23:31:41 -0500, default wrote:

Do the same to the right channel.

Change that to "Do the same to the left channel."
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WHy not use an RCA "Y" Adpter? Under $2.00

On Thu, 17 Nov 2005 09:03:25 -0600, "DBLEXPOSURE"
wrote:

WHy not use an RCA "Y" Adpter? Under $2.00

You can, providing that the impedance of the line out is high enough
to tolerate the loading, or the circuit is short protected. Low
impedance outputs will merrily self-destruct when shorted. The other
disadvantage is that the output of one channel may affect the feedback
in the other channel if it uses op amps.

Better safe than sorry, and the sound will be cleaner.

The minimal extra effort required seems well justified IMO.
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"default" wrote in message
...
On Thu, 17 Nov 2005 09:03:25 -0600, "DBLEXPOSURE"
wrote:

WHy not use an RCA "Y" Adpter? Under $2.00

You can, providing that the impedance of the line out is high enough
to tolerate the loading, or the circuit is short protected. Low
impedance outputs will merrily self-destruct when shorted. The other
disadvantage is that the output of one channel may affect the feedback
in the other channel if it uses op amps.

Better safe than sorry, and the sound will be cleaner.

The minimal extra effort required seems well justified IMO.
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You mean the impedance of the input you are feeding is high enough not to
load down the cd player's line output? If you are plugging into an RCA type
connector chances are it is high impedance.

I agree, do not do this at 600 Ohms. Use a combining network.