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Passive Mixers

#21
I'm glad you got it working.

If we look at the output pot and label the tabs 1 2 3 where 2 is the middle one: tab 1 should go to the opamp, tab 2 to the output, and tab 3 to ground. If you don't like the direction (i.e. as you turn "up" it gets quieter) then reverse 3 and 1. But 2 is always the output.

An audio taper will probably work better.
 
#22
seanm said:
I'm glad you got it working.

If we look at the output pot and label the tabs 1 2 3 where 2 is the middle one: tab 1 should go to the opamp, tab 2 to the output, and tab 3 to ground. If you don't like the direction (i.e. as you turn "up" it gets quieter) then reverse 3 and 1. But 2 is always the output.

An audio taper will probably work better.
Click to expand...

yeah I will try grounding that last pole in the morning...

I wonder if I can try to return the pots and buy audio tapered ones...

maybe not since I already soldered 'em... i got 'em from radioshack
 
#23
Sir Edward V said:
yeah I will try grounding that last pole in the morning...

I wonder if I can try to return the pots and buy audio tapered ones...

maybe not since I already soldered 'em... i got 'em from radioshack
Click to expand...

If they are anything like the electronics store I go to, then I highly doubt you will be able to return them once soldered.

If you can afford to get audio ones with out returning the linears, thats what I would do. Pots always come in handy :)
 
#25
They let me return them :D

so now i have the new ones in and the output pot doesn't really work that well, it works until it is about maxxed out, then it just cuts out the sound...

two 100k audio pots for input, and a 10k audio for the output, cause they didn't have a 50k audio and that was the closest I could find
 
#26
Sir Edward V said:
...simple question: How well do they work?

I know several people have used them here, I have heard stories about them not always working. Why wouldn't it work well?

Informed responses only please. :D...
Click to expand...
I was looking at a schematic for the... the Dynacomp, I think it was. That thing had.. what was it? -a ten-thousand Ohm output impedance - now I would imagine that THAT would surely cause problems with a 'resistive mixer'.

I'm pretty sure that they're expecting them to be driven with a LOW impedance source! Anything with a 'buffered output' should be fine, I'd think.

Joe
 
#28
Sir Edward V said:
They let me return them :D

so now i have the new ones in and the output pot doesn't really work that well, it works until it is about maxxed out, then it just cuts out the sound...

two 100k audio pots for input, and a 10k audio for the output, cause they didn't have a 50k audio and that was the closest I could find
Click to expand...

Try moving the output cap C11 *before* the volume rather than after.

And why not use a 100k audio for the output?
 
#29
seanm said:
Try moving the output cap C11 *before* the volume rather than after.

And why not use a 100k audio for the output?
Click to expand...

so put that cap in between the output on the opamp and the one rung of the volume pot?

well its a little late for that switch now... I already clipped the pots. I really don't think I'm going to change anything though... the thing isn't perfect, but it works and I don't have a reason to change the settings, so until I run into a problem I am going to let sleeping dogs lie.

What I actually did was convert the ABY box I made earlier this year into this pedal. In the process of testing it I overloaded the LEDs... Now I need to buy new ones...
 
#30
DSCF1120.jpg
 
#37
niftydog said:
You know that kind of thing is illegal in most states, don't you Ed?
Click to expand...

how would you know? you're Australian! :hiding:

anyone notice the LED on the left looking strang/dark?

well I fried it accidentally when building this, the other one is shorted out right now I think, but I haven't felt like fixing it. I will whenever I buy a replacement for lefty

but I have been thinking... I don't change the settings on this thing ever... nor have I been using the switches... maybe I will change it so I can use some parts on other things...

or maybe I will leave it so I don't have to worry about it breaking!
 
#39
adding more discussion for the guy that just posted a new thread wanting to build a blender

today I fixed the LEDs and the output pot that was still scratchy

Overview: what I did was use seanm's schem, added 100k audio pots before the input resistors with the third lung grounded, made R10 a 10k audio pot with the third lung NOT grounded, the ground is -Vcc and not what is labeled as the ground, R11 isn't there, Rload isn't there, C10 is 33pF because that was the closes cap I had... and I think that about covers it!

It is perfect now as the input voltage (volume) is equal to the output voltage when the pot is all the way up (10k/10k = 1).

Note: For the switching I have one switch turning off the input source and the other turning off the effected source.
 

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