How to convert stereo into mono ?

[SA Dev]

Hi,

I am going to be using an amp from
http://www.canakit.com/Contents/Items/UK193.asp. I am taking a line output
from a PC sound card and wish to power one speaker with it. My questions
are:

1. How can I combine both the left and right channels from the sound board?
Can I just connect them together?

2. How does input sensitivity work?

Thanks,

Alan

 

[Walter Harley]

1. How can I combine both the left and right channels from the sound board?
Can I just connect them together?

No. Think about what happens in that case when the signals are different:
each output is trying to force the other to be something other than what it
wants to be. Depending on the sound card, this could cause damage.

Connect the grounds all together. Then connect the hot lead from each
channel to a 4.7k resistor, and connect the other ends of the resistors
together, and connect *that* to the input of the amp.

Or, if your software permits, mix to mono in software and then just use one
channel.

2. How does input sensitivity work?

That kit says it's specced at "100mV/47k". That means that the input
impedance is nominally 47k ohms, and that 100mV signal is enough to drive it
to full output (if the volume is all the way up).

By the way, before you go taking the 22W rating of that kit too literally,
you might want to dig up the spec sheets for the TDA2003 (the chip it's
based on) and seeing what kind of power, distortion, and frequency response
you can actually expect.

 

[SA Dev]

Walter,

Connect the grounds all together. Then connect the hot lead from each
channel to a 4.7k resistor, and connect the other ends of the resistors
together, and connect *that* to the input of the amp.

Thanks, I found this page today:

http://www.hut.fi/Misc/Electronics/circuits/linesum.html

It recommends using 10k resistors. Would both work equally well? Would the
4.7k's you suggest work better for the amp I plan to use?

Thanks a bunch for your help,

Alan

 

[Martin Riddle]

4.7k or 10k will work equally well. This creates the classical Summing amplifier input.
You may notice some volume differences between the two, So you might want to experiment with your
particular setup.

Cheers

 

[Active8]

Hi,

I am going to be using an amp from
http://www.canakit.com/Contents/Items/UK193.asp. I am taking a line output
from a PC sound card and wish to power one speaker with it. My questions
are:

1. How can I combine both the left and right channels from the sound board?
Can I just connect them together?

you'd use a summing amp, i'd think. if your sound software doesn't
support mono, you could try the Creative Lab's SB -- some abbrev for
Sound Blaster Hardware Programmers whatever. you can get the C code to
code your own stuff. the sample code had a recorder/player with the mono
option.

2. How does input sensitivity work?

you stick your hand under running water and turn up the temp until it
hurts.

input sensitivity of what? you need so much input signal to acheive a
given S/N ratio, basically.

summer below.

hope this helps.

mike

Thanks,

Alan

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