Wednesday, 28 November 2012

Building another O2+ODAC combo

The past few days I've been building another Objective amplifier+DAC combo for a guy at

He ordered the stuff and got it sent to me, I picked it up on monday afternoon and started building directly. The first evening I finished most of the O2 board, except one of the battery terminals and the power connector.
On day two I sanded the legs of the power connector to make it fit through the holes and I used a glove to mount the last battery terminal (it gets very very hot!). For that job I borrowed a dremel copy from my neighbour. It was the first time ever I was using a dremel but it was simple and straight forward. Really liked it!

I then measured all the voltages and everything was fine, well under the limits. Tested it briefly with my phone as a source and a pair of old crappy headphones connected to it. Everything sounded as it should.

It was then time to mount the ODAC to the O2. Again using the dremel to cut the bolt from ~40mm to ~10-15mm. Very handy but it made a nasty noise. Found a broken CAT5-cable in a drawer and cut off ~10cm and took two of the pairs and stripped the insulation. Only strip a couple of millimeters here, not a centimeter as with speaker cables. Solder them to the board the right way this time, not as I did with my own amp.

Time to test run everything. Hook it up to the computer and test play it. No sound. No matter how hard I try there's no sound from it. I start double-checking all the wires and solder joints, nothing wrong. I try moving the ground cables to another spot on the board, no success. Then it hits me, maybe I didn't cut the traces on the O2 board well enough. The PCB was black so it was very hard to see. I look a sharp object and started scraping some more on the PCB and apparently they weren't entirely cut off. Cut them off properly and then it worked as it should.

Listened to it the whole evening and it sounded very very good, as it should. The product is now packed back into its box and I will ship it to the buyer tomorrow.

All in all it has taken me about 5-6 hours in total to build it. Much faster than the first time, because I knew where all the parts should be, I knew how to measure the voltages and I knew how to connect the ODAC to the O2. If you're a beginner and has very little or no knowledge of soldering and electronics, it might take 10-20 hours.

If you're interested in letting me build one for you, just send me an e-mail or write a comment or something.

And here's some pictures.

It's very nice to have a dedicated table for this!

All resistors marked and ready

Sanding the legs of the power connector with a dremel tool

My amplifier (the black) and the new silver one.

Up and running. The LED isn't yellow, it's red, it just looks yellow in the picture. 

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