lørdag 2. mai 2015

DAC board soldered too

I finished something else yesterday - the DAC board prototype. My first real 0.5mm pitch soldering job. I think it turned out alright, I did as bwack suggested and tilted the card under the microscope. It looks good to me.

I can't test it with the sample and hold circuit just yet as I have no angled connectors for some reason. I may try just the DAC tomorrow though.

The DAC is an AD5547 dual output parallell input 16 bit device. There are two reasons I selected this. First of all, I selected the parallell version as I thought maybe I could load it faster than if I went for the SPI version. Second, I was not sure if I could load 32 sample and holds fast enough with only one DAC, this allows me to load two at the time before clocking the result into the sample and hold. The dual version costs significantly more than a single one though, so hopefully I'll get away with one channel. The sample and hold card lets me select which channel I want to use for output 17-32, so I can test both single and dual channel versions.

The DAC chip with its tiny legs. My index finger for measure.

Through the microscope. Before cleaning away the flux obviously

I had to add this as well, I am really impressed with the quality of the OSH park silk screen! Look at those sharp lines (this is at 80x magnification I think)

The DAC card with two high quality AD8672 opamps. I have socketed these to be able to switch between these and TL072s to see if I can hear any difference - the AD8672 is about $5 and the TL072 is $0.50, so if I cannot hear any difference I'll just go with the TL072.

The DAC and sample and hold together but not connected. The large white header is for analog power, digital power comes thru the 36 pin connector to the left.

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