VOGONS


First post, by Kahenraz

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I'm hacking together a modified sound solution inside a thin client and would like to build a small audio mixer on a proto board to combine the sound between two different audio connectors. The primary reason for this is that the add-on PCI card will be using VXD drivers, and the onboard will be WDM. The advantage of this is that I can combine the legacy compatibility of the VXD drivers with the luxury of the WDM MIDI mapper, which includes options such as Microsoft's GS and Yamaha's XG software synthesizers.

I will be removing the onboard connector and adding solderable 3.5" audio jacks. I don't know much about combining audio signals, but it doesn't sound right to me that I would just solder the signals from the two cards onto the same connector. This would effectively be connecting the amplified output of one card to another, and I don't think that's a good idea.

What would I need to build a small mixer for my intended purpose? It would mix the audio outputs, which I think are amplified and not line-out, together. I'm not even sure if it's line-out or speaker out. Is there an easy way to tell?

Reply 1 of 3, by Pickle

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your right you cant short the two signals together.
what you really need is a line in on one of the cards and connect the line out from the other then the built in mixer can handle it. I do this with a audigy 2 and a vortex.
i think for external hw using two analog to digital converters and then you can combine the two numeric values and use that to output out on an analog output.
but i think that would still likely need some type of a microprocessor. maybe an rpi with a i2c sound modules.
but make sure which ever way you go the outputs are not amplified.

Reply 2 of 3, by imi

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you can't "just" short the signals together, but you can if you put resistors in between, that's essentially what a passive mixer is, just with variable resistors, and you can also get those ready made for cheap in a very small form factor.

obviously you should make sure that all the devices are roughly at the same signal level though, and I'd certainly use line level for that and not an amplified output, mostly every sound card should have a line out.

Reply 3 of 3, by Tiido

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The most easiest functional way is this :

easymix.png
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Use a 10kohm pot per signal pair and keep the output wire short, impedance of the signal is much increased and it will easily pick up noise and interference compared to a proper active design.

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