Need to build cheap PC mixer...

[pcmixerguy]

Hi all , I'd like to make an easy PC circuit to help out all those who are in a situation similar to mine..
- Six years ago, I started with 2 PC's and trained enough to work full-time in computers. After time and some perks, I found quite a number of PC's gathering at home. While interesting to look at, they really weren't doing much for my carreer untill the next perk: a 4x1 KVM switch.. (small KVM's don't do much with audio ).
At first I daisy-chained 4 PC's, but I soon found level problems, buzzing and over-all frustration with software volume controls. Add to that, the need to run all PC's if I want to hear the first one in the chain.
I don't need to switch audio, but I do need to mix it - cost effectively...
- I'll build the circuit and post a pic and public 'how-to' on these assumptions: (suggestions welcome..)
1. It must be cheap, easy to build, easy to use, and use absolutly no power supply.
2. Most amplified PC speakers have more than enough gain that this can be done with a passive circuit.
3. Most non-amplified sound cards (< 5 years old) have enough gain that this can be done with a passive circuit.
4. I care about sound (so do you? ) so, I want to use a capacitor coupling to stop buzzing sounds, without using the wrong size to steal away the lower bass sounds or muddy the sound up. I elect not to use a capacitor on one of the four inputs so I can dedictate this to the best sound card I have. (ahem, my tunes box)
5. Those who share my plight typically have a desk, so they should have enough room to fasten a flat strip of metal, on which to mount the parts and 4 volume controls.

I'm going to use four 10k-ohm dual-pots in parallel (that's 2.5k ohms), 50mfd input capacitors, and nothing more..
I'll post this month pending results, group interest and rejection. See ya!

[then]

Sounds like worth to document project.

I have built something quite similar what you are aiming to,
only for two audio channels though. My circuit is called
Simple line mixer and the details of it can be found at
http://www.epanorama.net/circuits/linemixer.html

You can take a look at it for some ideas.

Some notes on your articles: generally using
a capacitor coupling to stop buzzing sounds does not
help in this problem. The buzzing sounds in this kind
of systems are generally caused by ground loop
currents, poor grounding arrangements or poor circuit shielding.
Having the capacitor on the audio path will stop DC getting
to potentiometers, whixh is generally a good idea (for example
potentiometers make less noise when you turn them when there is
no DC over them, if the signal source has some DC coming out, then
capacitor blocks it).

I hope you success with your project.

[d vibe]

Hello, I'm new here... Sorry for bumping such old thread, but I thought that it would be more appropiate to use this one rather than creating a new thread.

My question about your simple mixer circuit (http://www.epanorama.net/circuits/linemixer.html) is a very small one. Would it work to remove two of the four pots and just connect those two channels directly to R7 and R8 (or R5 and R6 ofcourse) ?

I'm going to always have full volume on those two channels anyway.


Btw, I tried to e-mail Tomi on two addresses (one of them is the one in the circuit scheme) but none of them worked. Too much spam to them perhaps?

Sincerely
/Daniel, Sweden

[Tomi Engdahl]

My question about your simple mixer circuit (http://www.epanorama.net/circuits/linemixer.html) is a very small one. Would it work to remove two of the four pots and just connect those two channels directly to R7 and R8 (or R5 and R6 ofcourse) ?
I'm going to always have full volume on those two channels anyway.

Yes.
And you can add more channels to the design in the same way and the ones you already have.
So just add more resistors like R7 and R8 to add more channels (directly or though potentiometer).
This circuit should work quite acceptably to 5-6 and after that the attenuation could go a bit high side...

Btw, I tried to e-mail Tomi on two addresses (one of them is the one in the circuit scheme) but none of them worked. Too much spam to them perhaps?

Too much spam has been a quite big problem for a long time...
But the real reason those e-mail addresses do not work anymore are that they point to Helsinki University of Technology, and my e-mail account there ended just a short time ago...
Thank you for your feedback. I put updating the e-mail addresses on the documents to my "todo" list... first I have to decide what e-mail account I want to fill with all the spam that gets to whatever address I put there...