volume out ---- =S

[kitsophrenik]

soooooooo! im halfway through another project and im tryin to wire the audio outs of diff circuits together... the sound doesnt dip when im wiring them all to a common out which is good... im just wondering how would i wire a pot (lin or log) ,,,, (think lin) lol in line with the audio out so i have a master volume level control before the final output.......................


do i just wire it in lthe positive line/rail then to the out put... or do i have to have 2 pots one for neg and one for positive?


any help would be very much appreciated! =D

cheers guys....

p.s also sorry i havnt posted for a wee while but the truth is i just havnt made any gadgets fora bit... been on with other music orientated stuff... also any links to subbox design / speaker design scems or plans would be helpfull! just tryin to build 2 18" sub/bass bins for us soundsystem atm..

Cheers! 

[Circuitbenders]

This kind of depends how you've mixed the signals together. If you've just wired the outputs together you might get away with wiring the output to one side of a pot, wire the other side to ground and the centre pin is your output. I guess a 10K Log pot might do the trick. Bear in mind though, that at zero volume you'd be essentially pulling both outputs to ground which they might not take too kindly too.
If you don't already have them, you'll probably need at least a couple of resistors just before you wire the two outputs together and stick in the master volume pot. Do a search for passive mixer schematics and you'll find a few that will work.

What would be better would be something like this:



where the opamp buffers the signal. It will sound a lot better and won't produce any unexpected results.

[kitsophrenik]

ahh.. welll at the mo all 4 circuits im wiring tgether are running from the same power source and were all just wired together into the same output.... i was trying to avoid having to buy any more resistors etc so i could get it finished this weekend! lol =D

... do you think the mixer circuit for the output is worth doing then?

i mean ive had then twisted together just to test the output to see if it dips or distorts but it seems to work ok.. to be honest the machine im making isnt so i kan blast out all 4 sets of functions at the same time its just more so there in the same box... kinda accesable from the same power etc... just a box of different sounds ... sorta!

ive got a 500k log (ithink!) slide pot for them to wire to... so ill just wire tht up how you said... when you say wire one side to ground thts just the far side of the pot then?> so i wire into 1 side with lets say +possi then negg - the other far side then the middle pot is strate to my output jack?


cheers for the elp! 

[kitsophrenik]

or by ground do you mean an earted point on one of my boards? ??

[Circuitbenders]

the negative lead of the power supply, the ground of the output jack, the earth/ground of the boards, they're all the same thing. They should be anyway or you're going to come up against some problems.

If you're not going to go with the opamp method i would recommend sticking something like a 4.7-10K resistor on each input before they come together. Something like this will probably do the job:



I'm not sure what you mean by 'i wire into 1 side with lets say +possi then negg'. The middle pin of the pot goes to your output jack tip, the left or right pin to ground, the remaining pin to the mixed signal from your devices. It doesn't matter which way round the ground and signal are, it'll just change which way the pot turns for volume up and down.
I guess thats what you mean?