[ProFingerSk8er]

hi guys, i want to add muti-input to my amp that can be turn off with a switch.
i was thinking hooking up the switch on second input's ground wire to block out it's single, but im wondering if both inputs are playing with the second input's ground wire block off, would the singel from second input interfear the other input?

thank you

 

[ProFingerSk8er]

sorry if i didnt make it clear...

so is this possible or no?
if no, can anyone help me with muti-inputs?

 

[viviorunitia4]

You could just use a DPDT switch to switch between left and right inputs and connect the grounds. I'm not sure if there would be any benefits to using either switching scheme. I think that switching only the signal and sharing grounds is more commonly used.

 

[ProFingerSk8er]

thanks for the reply, i thought of using DPDT switch. but i was wonder if i can do it this way so maybe i can use both input at the same time..
like one onput from my computer when gaming and the other input from my iHP so i can enjoy my own music while gaming through my headphones...

anyone know if this is possible?

 

[guzzler]

you'll need to make a mixer to do that... try Elliot sound for a simple 2 channel mixer

g

 

[ProFingerSk8er]

thanks guys, and can you possible link me to the Elliot sound simple 2 channel mixer?

also....i found this site on how to build a mixer circuit
link: http://www.hut.fi/Misc/Electronics/c...s/linesum.html
if im understanding this correctly, i can just add some resistor somewhere on the inputs before they joint togather?
if this is possible i have some left over resistor from my amp. if someone can help me out with this i will greatly appreciate it

or is this not a good solution to channel mixing?
im just trying to make it as simple as possible to fit into my amp (which isnt really limited caus im making a new case too)

thanks again

 

[guzzler]

http://www.sound.westhost.com/project94.htm

not as simple as i remember! and don't use the TL072 opamps: icky!

the load sharing resistors will work, but i won't say i have any idea how good they would be!

g

 

[ProFingerSk8er]

wow...i think i got dizzy from looking at those charts...lol
i think this is too confusing for me...ill havta go with a simpler solution.

im guessing using resistors to make a simple mixer will degrade sound quality. im rebuilding this amp to be used with my computer. is there a simple and good way to mix channels? or it is not as easy and not worth doing at all?

thank you to those who had helped me soo far... being a noob is never a good thing

 

[phaedrus]

I've built two of the circuits from hut.fi, your link pro. One is a 2:1 mixer and the other is a 3:1 mixer. Both work great. I've also got parts here for the one guzzler suggests, but not time to tinker until the semester ends.

 

[phaedrus]

Hrm, looked at that again and I added panasonic pots for each channel in so that I can fine tune the levels going into the amp.

 

[ProFingerSk8er]

thanks for the info phaedrus, so that circuit should work quite well right? and could you please link me to that 3:1 mixer as well..
and if you dont mind, would you please let me know what resistors did u use? i got 1.00K, 4.75K, and 10.00K leftover resistors from my amp.
and where does the resistors go? ground line or right/left line?

and did you noticed and sound difference with this circuit?

thanks a lot for all the help, i really appreciate it

also, where should the switch go if i want to be able to turn off the second channel? or is it not a good idea to only block off ground?

 

[ooheadsoo]

I'm in the same boat as pro, except i'm an even BIGGER NOOB than he is. The hut.fi link looks really good. Please let the discussion continue, I'm trying to soak all this up without my brain imploding. If we could get some pictures of what we're talking about up, it'd be great! I'm in the middle of studying the hut.fi link now.

Edit: If we wanted to build this circuit into the enclosure of our amp, we would leave out the male rca connector at the end of the circuit and wire it directly to the input of our amp right?

 

[ProFingerSk8er]

Quote:

Edit: If we wanted to build this circuit into the enclosure of our amp, we would leave out the male rca connector at the end of the circuit and wire it directly to the input of our amp right?

yes, that's exactly what im planning to do, so if more people can help us out it would be great

 

[A3rd.Zero]

It might interest you to know that a volume pot (or balance pot for that matter) is just a variable resistor. Therefore if you buy yourself a liner balance pot at 10k or 20k and place one pole where one of the resistors is and another pole where the other resistor is then you will be able to pan between more music or more game. You will need a 4 pole balance pot for this to work in stereo. This will give you a very basic "mixer" rather than a "summer"... or "winter" .

Milo

PS i know that this is a short hand explanation but if you want to try it i will further explain how to make this work.

 

[phaedrus]

I apologize for the slow reply -- been down with what ever is going around.

The hut.fi schematic is for two single channels combined into one line out. It has to be multiplied to accomodate multiple stereo inputs. My setup goes:

1/8" in (1L & 1R) --> 10k pot (1L & 1R) --> 10k resistor on the pot out lines --> \

1/8" in (2L & 2R) --> 10k pot (2L & 2R) --> 10k resistor on the pot out lines --> -|--> switchcraft 1/8" (123L & 123R) on the opposite side

1/8" in (3L & 3R) --> 10k pot (3L & 3R) --> 10k resistor on the pot out lines --> /

The ground is tied together all the way through -- I ran a wire connecting the three input grounds to the three pairs of pot grounds to the output ground using no resistors, similar to Chu Moy's tutorial for a switch or crossfeed over on headwize, if I recall the tutorials correctly. I used Vishay-Dale resistors, Panasonic 10k pots and Switchcraft 1/8" mini jacks.

I managed to fit it into a plastic hammond case that I got locally on clearance. It is 1.25"X2"X1.25" more or less, so the pots pretty much have to sit at an angle. I'd do it in a larger case were I to do it again.

I'm not sure what the limit of usefulness is with this circuit. I tried 3 lines as that is what I wanted to solve my problem at the office and it worked. I had ordered parts for powered fet based mixer (http://www.aaroncake.net/circuits/mixer1.htm) and this was a way to kill the time until the postal service dropped my package. It worked sufficiently well, however, that I've not gotten around to building the replacement.

Also, since I built this a year or so ago, googling for "9v line mixer" yields the following goodie:
http://www.discovercircuits.com/A/au-mixer.htm

As always, I have wrapped electronics information around my head in an as yet limited fashion, pretty much don't know what I'm doing and your mileage may vary.

And, one final note -- at the time I built this mixer I did not know that a pot was a variable resistor, as A3rd.Zero reports. That this tidbit of information has been assimilated in some sort of limited degree is progress in my book.