simple Mix two channels into one

hi.

I want to make a stereo source mono, using only a passive device, and I want minimum signal attenuation - the fewer resistors the better!

I'm not sure if the output needs to be a stereo plug or a mono one, hence the two sets of diags.

As such, which of these could I use (I would prefer to use 2/4 because it uses less resistors than 1/3). Also, what are the minimum resistor values I could get away with.

Cheers,

Tim

Number 2 should work, commonly used in philips amp's to force mono...

resistor values depends on the device ouputting the music and the device wich gets the signal as input...

Only use such a setup between a preamp and and poweramp.
dont try this on the output of a poweramp

Exo said:

resistor values depends on the device ouputting the music and the device wich gets the signal as input...

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damn, I was hoping to use it for a variety of things. What do you reckon for a portable CD player, into the 'aux' input of a Hi-FI?

Exo said:

Only use such a setup between a preamp and and poweramp.
dont try this on the output of a poweramp

Click to expand...

why?

grrr_arrghh said:

damn, I was hoping to use it for a variety of things. What do you reckon for a portable CD player, into the 'aux' input of a Hi-FI?

Click to expand...

It's common practice to just join the two outputs together, no resistors required - ideal for phono socket outputs on a CD player to a mono amplifier (usually a PA or guitar amplifier). The output impedance of the CD player basically replicates your diagram 2 or 4.

Exo said:

Only use such a setup between a preamp and and poweramp.
dont try this on the output of a poweramp

Click to expand...

why?

Click to expand...

Because the outputs are far higher levels, you could do it with resistors (again like 2 or 4), but you would need higher values.

It's common practice to just join the two outputs together, no resistors required - ideal for phono socket outputs on a CD player to a mono amplifier (usually a PA or guitar amplifier). The output impedance of the CD player basically replicates your diagram 2 or 4.

Click to expand...

:? In my other thread, about the headphone amp, I thought you were suggesting that the output on a (for example) portable CD player was a power amp, to power headphones or whatever, but you and Exo say this shouldn't be done between a power amp and something...? Or did you think I was talking about a normal standalone CD player? (I'm talking about a walkman type cd player...)

Have I misunderstood something here? Probably!

Thanks

Tim

grrr_arrghh said:

It's common practice to just join the two outputs together, no resistors required - ideal for phono socket outputs on a CD player to a mono amplifier (usually a PA or guitar amplifier). The output impedance of the CD player basically replicates your diagram 2 or 4.

Click to expand...

:? In my other thread, about the headphone amp, I thought you were suggesting that the output on a (for example) portable CD player was a power amp, to power headphones or whatever, but you and Exo say this shouldn't be done between a power amp and something...? Or did you think I was talking about a normal standalone CD player? (I'm talking about a walkman type cd player...)

Click to expand...

The output of a CD walkman is (as you say) intended to feed headphones, but it's also designed to feed line inputs - you're only talking very small power levels, joining them together shouldn't cause any problems.

As a matter of interest, why do you want to connect a stereo source to a stereo amplifier, and make it mono?.

As a matter of interest, why do you want to connect a stereo source to a stereo amplifier, and make it mono?.

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lol, well, hmmm.
To start with, I wanted something along the lines of diags 3/4, because I'm going away camping next week, and we have a battery operated karaoke machine, and we want to use it as a speaker for our cd player/mp3 player etc. (if your interested its replacing the headphone amp and lil' speakers in the other thread I mentioned). Anyway, being a karaoke machine, it only has one speaker. The reason for also wanting something like diags 1/2 is because when I'm listening to the TV on my computer, through headphones, the two channels are too different, and its really annoying, and I can't be bothered to build one of those spatial thingymbobys, and I thought I might as well combine the two.

The output of a CD walkman is (as you say) intended to feed headphones, but it's also designed to feed line inputs - you're only talking very small power levels, joining them together shouldn't cause any problems.

Click to expand...

ahhhhhhhhhhhhhhhhh. I understand

Cheers,

Tim

grrr_arrghh said:

To start with, I wanted something along the lines of diags 3/4, because I'm going away camping next week, and we have a battery operated karaoke machine, and we want to use it as a speaker for our cd player/mp3 player etc. (if your interested its replacing the headphone amp and lil' speakers in the other thread I mentioned). Anyway, being a karaoke machine, it only has one speaker. The reason for also wanting something like diags 1/2 is because when I'm listening to the TV on my computer, through headphones, the two channels are too different, and its really annoying, and I can't be bothered to build one of those spatial thingymbobys, and I thought I might as well combine the two.

Click to expand...

Diagram 4 is fine, but you may as well not bother with the resistors (I wouldn't bother with them), just make a simple lead up, soldering the tip and ring connections in the 3.5mm jack plug together - presumably to a mono 1/4 inch jack plug?. I made that exact lead earlier this year to provide music for a charity martial arts event we ran, connecting my daughters CD walkman (that I 'borrowed' without asking) to a small portable PA amplifier - it worked perfectly!.

you presume correctly!!

cheers Nigel,

Tim