Any resistor can be replaced with a trim pot if you want to experiment. Combining the two raw inputs can lead to phase cancellations and distortions, like with the y cable...
Last edited by chunter (Jun 11, 2013 9:05 pm)
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Finland
chunter wrote:
Any resistor can be replaced with a trim pot if you want to experiment. Combining the two raw inputs can lead to phase cancellations and distortions, which may or may not be a desirable thing for you...
Well. ATM I have limited amount of things to play around with. The resistors I have on hand are 4.7kohm resistors. I guess that's kind of a lot am I right?
I used those because of this tutorial.
But I can't really be sure of how the creator has planned that to be used.
But on the build with the resistors I had one per channel per jack, which means I end up with two wires going to the left and right channel respectively and both those have resistors on them, I guess I could condense it down to having one resistor per output channel?
Here's the cheeky schematic I used. Look it over but please be gentle, I haven't done this in the past. *blush* xD
But I reckon maybe it's overkill to have 4 resistors like that? Should I test with only one resistor per channel then? :S
Last edited by my.Explosion (Jun 11, 2013 9:13 pm)
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Germany
dont you have one resister per channel? afaik the resistors are for the inputs not going back into the other input.
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Brunswick, GA USA
Altoid guy used 1k+ resistors because his mixer has no level control pots.
Last edited by chunter (Jun 11, 2013 9:39 pm)
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Finland
OK.
Thanks for the response guys.
As I see it: If this thing in fact works with no audible distortion (I didn't get a lot of time to test it out, I will continue fiddling with it in the morning) then any and all problems should start arising when I plug in different devices to the inputs right, or to the output?
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Germany
well afaik there should be at least some resistance to protect the inputs.
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Finland
Bamboori wrote:
well afaik there should be at least some resistance to protect the inputs.
Allrighty. 
So should it be input -> resistor -> pot -> output?
In the schematic I have it the other way around, the resistor kicks in before going through the output jack.
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Germany
i think that wont make a difference, since the pot is used as a variable resistor, so both add up no matter which order they are in (as long as they are in a row).
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Finland
Bamboori wrote:
i think that wont make a difference, since the pot is used as a variable resistor, so both add up no matter which order they are in (as long as they are in a row).
Cool. Yeah. I completely misunderstood what you meant. I mixed up my terms. 
But thanks! I'll get to work on this in the morning, see if I can't get this contraption to fit inside a plastic case of sorts...
I'll also see to it if I can't get some resistors with less resistance tomorrow. e_o
Last edited by my.Explosion (Jun 11, 2013 10:15 pm)
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Jelly Stone park, MD USA
Guys, If you only have say 1K resistors on hand you can put two in parallel for a total of 500ohms. I.E. putting 3 in parallel would give 333ohms . The Equ for parallel:
Rtotal=1/((1/R)+(1/R)+(1/R).......)
Use this for any number and value of Rs in parallel. They don't have to be all the same when solving for Rtotal.
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Finland
yogi wrote:
Guys, If you only have say 1K resistors on hand you can put two in parallel for a total of 500ohms. I.E. putting 3 in parallel would give 333ohms . The Equ for parallel:
Rtotal=1/((1/R)+(1/R)+(1/R).......)
Use this for any number and value of Rs in parallel. They don't have to be all the same when solving for Rtotal.
That's right. But in my case I'm kind of space restricted so to parallel 2 or more resistors takes up a lot of space. So I think my best bet for this mixer project is to land a good resistance with only one resistor.
That's also what I've been thinking about since yesterday. I'm guessing there's no other way to know when my resistance value is good than to just test various right?
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Jelly Stone park, MD USA
As Chunter pointed out above, use a pot in place of the R. In a test circuit, adjust it to your liking, Then remove and measure the value with a multimeter. You can then replace with a fixed resister.
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Finland
yogi wrote:
As Chunter pointed out above, use a pot in place of the R. In a test circuit, adjust it to your liking, Then remove and measure the value with a multimeter. You can then replace with a fixed resister.
Valid point. I'm probably going to have to invest in a multimeter for future projects- I've just started with building custom stuff. ^^
But yes- I'm finished with my little mixer project. Finally settled on 560ohm resistors, I have two for each channel. There's no real audible phase cancellation like in my last attempt where I accidentally soldered the input from both channels to a shared junction where the resistor was situated. That build was catastrophic, super faint sound, even weaker when two devices went off simultaneously.
But my new build is about as good as I care to get it right now. I ended up omitting the potentiometers in the end. I don't have enough room for them in the case I have. It's a small black plastic box about the size of a Game Boy cartridge case and actually has the top fashioned from such a case since I didn't have any other plastic at hand. It's all wrapped up in tape so it's a sight for sore eyes. But it works.
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Jelly Stone park, MD USA
my.Explosion wrote:
Valid point. I'm probably going to have to invest in a multimeter for future projects- I've just started with building custom stuff. ^^.
yea, good investment if you plan to do more
my.Explosion wrote:
....and actually has the top fashioned from such a case since I didn't have any other plastic at hand. It's all wrapped up in tape so it's a sight for sore eyes. But it works.
Sweet. like'n the post-apocalyptic look
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Brooklyn, NY
Can't believe I haven't bumped into this thread before now!
I just started an online electronics shop and one of my products is a beautiful compact passive matrix mixer. You can find all the info on it here...
http://xiwielectronics.com/products/pas … trix-mixer
Unfortunately, I'm currently sold out, but am taking preorders for the next batch I'm putting together.
This version uses 100k Audio potentiometers with 100k mixing resistors. I used a higher value, because I imagine it being used by noise and feedback artists rather than for practical applications like a headphone mixer/distributor.
