Simple mixer circuit?

[DaveC]

I want to pipe music throughout a building using a 70-volt,
"constant-voltage" PA system. The amplifier has mono inputs and outputs.

I want to use a standard stereo CD-player as the source.

What is the simplest way to mix the two channels into one so as to avoid
the weird-sounding "half-stereo" sound when you use only one channel with
such a distribution amplifier?

I seem to remember a simple resistor network...

Thanks,

 

[Bob Masta]

I want to pipe music throughout a building using a 70-volt,
"constant-voltage" PA system. The amplifier has mono inputs and outputs.

I want to use a standard stereo CD-player as the source.

What is the simplest way to mix the two channels into one so as to avoid
the weird-sounding "half-stereo" sound when you use only one channel with
such a distribution amplifier?

I seem to remember a simple resistor network...

Thanks,
--
DaveC
me@privacynet
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Put a resistor in series with each channel and
tie them to the PA amp input. Put another
resistor from there to the common ground of
both channels and the PA input ground.
Use any convenient value in the 1-10K range
for all 3 resistors. If you want to also reduce the
level, make the input-to-ground value smaller.




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

[DaveC]

Put a resistor in series with each channel and
tie them to the PA amp input. Put another
resistor from there to the common ground of
both channels and the PA input ground.
Use any convenient value in the 1-10K range
for all 3 resistors. If you want to also reduce the
level, make the input-to-ground value smaller.

Can the third resistor be a trim pot? This way it could be a level control.

Thanks,

 

[Michael A. Terrell]

Can the third resistor be a trim pot? This way it could be a level control.

Thanks,
--
DaveC
[email protected]
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Yes.

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We now return you to our normally scheduled programming.

Take a look at this little cutie! ;-)
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Michael A. Terrell
Central Florida

 

[John Woodgate]

Can the third resistor be a trim pot? This way it could be a level control.

Yes, it can. For consumer audio interfaces, the output source impedance
can be as much as 2 kohms, so it would be best to avoid series resistors
below 5 kohms or so, to prevent distortion.

Since you are just summing the two stereo channels, you don't need to
consider what happens if one source is disconnected. But in the general
case, if you disconnect one source, the level from the other source goes
up. The lower you make the resistor to ground (the end-to-end resistance
if it's a pot), the less increase you get, but the lower the normal
output level.

 

[N. Thornton]

Yes, it can.

Or if you dont need the level control, 2 resistors is fine, no need for the 3rd.

Regards, NT

 

[Watson A.Name - Watt Sun, Dark Remover]

I want to pipe music throughout a building using a 70-volt,
"constant-voltage" PA system. The amplifier has mono inputs and outputs.

I want to use a standard stereo CD-player as the source.

What is the simplest way to mix the two channels into one so as to avoid
the weird-sounding "half-stereo" sound when you use only one channel with
such a distribution amplifier?

I seem to remember a simple resistor network...

Thanks,

You can use a simple "Y" cable from Rat Snack. Or I would put a
couple 10k resistors on the back of a triple RCA jack. One resistor
from each channel to the center pin of the middle jack, which goes to
your PA.


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[N. Thornton]

The reason for the third is to provide a DC ground return,
since inputs and/or outputs are often AC-coupled. May
not be needed in all cases, but much easier to include
it from the start than have to add it later,

It works perfectly with out it, it isnt needed. Its upto the in and
output devices if theyre cap coupled or not, but either way it'll
still work fine.

Regards, NT