Simple mixer circuit?

D

DaveC

Guest
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@privacy.net
This is an invalid return address
Please reply in the news group
 
On Fri, 16 Jan 2004 00:20:10 -0800, DaveC <me@privacy.net> wrote:

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
This is an invalid return address
Please reply in the news group
Click to expand...
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
 
On Fri, 16 Jan 2004 05:58:03 -0800, Bob Masta wrote
(in article <4007ed33.3943957@news.itd.umich.edu>):

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

Thanks,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
 
DaveC wrote:
On Fri, 16 Jan 2004 05:58:03 -0800, Bob Masta wrote
(in article <4007ed33.3943957@news.itd.umich.edu>):

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,
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
Click to expand...
Yes.

--
We now return you to our normally scheduled programming.

Take a look at this little cutie! ;-)
http://home.earthlink.net/~mike.terrell/photos.html

Michael A. Terrell
Central Florida
 
I read in sci.electronics.design that DaveC <me@privacy.net> wrote (in
<0001HW.BC2D643400117CB8F03055B0@news.individual.net>) about 'Simple
mixer circuit?', on Fri, 16 Jan 2004:
On Fri, 16 Jan 2004 05:58:03 -0800, Bob Masta wrote
(in article <4007ed33.3943957@news.itd.umich.edu>):

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.

Yes, it can. For consumer audio interfaces, the output source impedance
Click to expand...
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.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!
 
John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote in message news:<cV2CTGJELFCAFwZy@jmwa.demon.co.uk>...
I read in sci.electronics.design that DaveC <me@privacy.net> wrote (in
On Fri, 16 Jan 2004 05:58:03 -0800, Bob Masta wrote

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.

Yes, it can.
Click to expand...
Or if you dont need the level control, 2 resistors is fine, no need for the 3rd.

Regards, NT
 
In article <0001HW.BC2CDEBA0005A48EF03055B0@news.individual.net>,
me@privacy.net mentioned...
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,
Click to expand...
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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StopSpam@EveryChance.org (Bob Masta) wrote in message news:<40093aa1.1795387@news.itd.umich.edu>...
On 17 Jan 2004 02:09:08 -0800, bigcat@meeow.co.uk (N. Thornton) wrote:
John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote in message news:<cV2CTGJELFCAFwZy@jmwa.demon.co.uk>...
I read in sci.electronics.design that DaveC <me@privacy.net> wrote (in

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.

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

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,
Click to expand...
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
 
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