Audio Mixer Upgrade

In this instructable i'll show you how i will upgrade my Behringer Eurorack MX802A. The Behringer Eurorack MX802 is a nice 8 channel mixer i picked up a few years ago on Ebay for about $50. It was purchased for use as a portable Podcast Audio mixer and is now serving as my Microphone input for Skype calls. As my Podcasting audio mixer it was carried around in a case allowing me to record a podcast from anywhere with up to 4 people. The problem was i had to use my old Creative Soundblaster MP3+ USB Soundcard to connect the mixer to the laptop and even my home PC. That sound card is still being used as the primary sound card for my PC since the on board sound died. Now days portable audio mixers come with USB audio built in. So to help reduce the clutter around my PC and update the mixer to fit the specs of it newer cousins i figured it was time to Integrate the Soundblaster into my Mixer.

Materials Needed:

- Behringer Eurorack MX802A (any Audio Mixer will do)
- Creative Soundblaster MP3+ USB Soundcard (any USB Audio device with stereo inputs and outputs will do)
- Speaker Wire
- 1/8" Phone Jack
- Set of standoffs with screws

Tools Needed:

- Soldering Iron
- Phillips Head Screwdriver
- 3/32", 1/4 ", 9/64", 7/32" and 3/8" Drill bits
- Jewelers files
- Scribe
- Tin Snips
- Needle Nose Pliers
- Razor Blade
- Wire Cutters/Strippers
- Painters Tape

Updated 1/27/2012 with wiring fixes and a new feature. See Step 8 for the update. 

Step 1 Current Mixer configuration

As it stands right now the Main Output of the mixer goes into the Input on the Soundblaster. I then have the output of the Soundblaster running to a 1/4" Headphone splitter. One side take the audio out ot my PC speakers and the other dumps the audio output back into the Mixer through the Tape In. This allows me to record any channel from the mixer i have connected as well as any audio i have coming from the PC. This was handy when my Pod casting partner was on Skype. Sure there are software packages that will record both the input on the PC and Skype but there where no free options at the time. At the time i felt i had greater control over the overall sound quality with this setup. Weather there was a real difference or not, doesn't really matter to me. Plus it allowed me to monitor everything on my headphones plugged into the Phones jack on the mixer. I like to keep the Soundblaster tucked away and out of sight. If i used the Headphone jack on it the sound to the speakers would cut out and i didn't want to keep reaching under the desk to switch out the cables.

The idea now is to integrate the Soundblaster into the Mixer. Giving the Mixer the added ability to acts as a PC sound card. Allowing the mixer to receive audio from the PC, mix with outside sources and send it back to the PC. Not to mention eliminating all the clutter of cables and adapters used to connect everything together.

Comments

[DustySeven7]

If you want to bring the led of the sound card to top a easy way to do so would be a light pipe. Glue it to the led on the card, drill a hole in the top of the case for it, glue the other end of the light pipe.
That technique is used in a lot of products. mainly routers. smd is smaller and uses less power.
Hope that is a idea that can help you out

[jakdedert]

The light pipe for adding the indicator is a good idea. If the circuit board is single-sided, you might be able to simply drill a hole through it to get the fiber-optic through to where you need it. Simply pick out an 'unpopulated' part of the board and drill a hole, using a long enough bit to continue through the panel above. Of course, you may not be able to determine what's on the other side of the board. Perhaps a small notch could be filed along one edge of the pcb to pass the optic cable to the other side.

If I were doing this project, I'd consider enclosing (shielding) the Soundblaster to avoid any digital noise getting into the audio circuits; and would definitely use shielded cable for the interconnects. Also, while you're in there, a few dB of noise reduction might be realized by moving that power circuit outboard of the mixer, putting it into a small box like they do on more expensive units.

[Earthscum]

The power supply for these mixers (or, this particular mixer) is a brick. It connects to the back of the mixer with a DIN plug.

[jakdedert]

Oh duh...I've got the same mixer; although it was given to me and I've never used it beyond the initial checkout and minor repair. It came from the factory with several switches needing to be 'exercised'...had a bad hum and distortion until I did that, which is how I got it for free.

[mpilchfamily]

From what i've read these mixers are hit or miss brand new. But if its a good one then its a reliable one. Mine seems to do pretty good.

[clairey]

This is great! Picked up one of these for a fiver a couple of months back... I'd say this mod is definitely worth that much... :)

[Earthscum]

Very cool idea! I'm staring at the same mixer and thinking that I may need to bug my guitarist for my Edirol back, lol.

[kevintumlinson]

For the status LED, you could run a short piece of fiber optic cable from the LED to a convenient point in the mixer housing. It would transfer the light of the LED without the need to desolder and resolder the board.

Thanks for this guide. I have an old mixer I can certainly upgrade this way!

[mpilchfamily]

Good idea. But the problem still remains getting at any point at the top of the mixer without having to remove the main board. I think i'll open it up again tonight and see what i can do to get the status light moved. I should have an optical cable somewhere.

I'll post an update if i can pull it off and if i have an optical cable.