Over here, I showed off the fact that I made some nice looking coasters. I'd rather not do that again. So I'd like to get some comments before I send out my boards again. Considering that there is some many DIY DACS out there, why do another one? Well, quite simply, there was not one I could find that would meet my requirements: 1. USB only - for power and digital source 2. No capacitors at the output. At a high level, what I have in my DAC which I'm calling the pup1 is: USB -> PCM2707 -> I2S -> PCM1794/1798 -> IV stage So in some detail: The PCM2707 (U2) accepts the USB signal and converts it to I2S. The chip is running in self-power mode and is configured in a simliar manner to what is done in the gamma1 DAC. I had originally set it up as host powered, but the self-powered mode is a simpler configuration taking up less board space. The PCM1794/98 (U4) is setup as to accept the I2S. The implementation is setup as per the PCM1798 datasheet. This is slightly simpler than the 1974 implementation (saves a bit of board space). The IV stage is the same as the one used in the ezDAC. All kudos to Evan for his design. The only thing that I have done is change some resistor values to keep the ouput within available voltages (2V p-p). My choice of op-amps at the moment for this stage is either the LMH6643 or the THS4222. Power on this board is a bit of work. USB power is filtered with a ferrite right off the cable. From their there is a 3.3v TPS (U1) regulator to provide the 3.3v sections to the PCM2707 and PCM1794 and a 4.75V TPS (U5) regulator to provide the power for the analog section of the PCM1794. In both cases the power is run through another ferrite post regulation. To provide power to the I/V stage, a charge pump is used to create a negative rail. The charge pump I choose was the TPS60403 (U6) . This provides an unregulated -5V rail from the USB 5v source. Two regulators (U7, U8) are then used (one from the +5V and one from the -5V) to create +-2.5V. It is important to regulate the charge pumps output as the talk alot about the rail drooping under load. Post regulation there is again another ferrite as well as two rail capacitors to ensure that the output op-amp is feed properly. Given all that to create clean power, I've added a couple of "test points" to the board. In the default configuration they can be used to check the voltages of the various stages. However, if desired they can also be used to: a. run the output unregulated at +-5V b. run the entire board on a power supply other than USB. As a choice, I was originally going to go through hole like the gamma1. I then decided that certain components were too large, so I changed some of the larger components to 1206 SMD. So my PCB looks like this: Top: Bottom (showing Top silk for reference): I've got the schematic as a PDF file, but it is a little messy. It started as the schematic for a more complex design and then I took stuff off so it looks like a bit of a mess. I can attach is someone would like. The two things that concern me right now: 1. The placement of the de-coupling capacitors (C19 and C17) around U4 2. The fact that I don't have any resistors on the I2S lines. To more experienced eyes, am I in any trouble with what I am doing? As a final note, I like to says thanks to: 1. Evan for his ezDAC I/V stage 2. AMB and everyone who commented on the gamma1 project. Learned a lot just from following the development thread at Headwize 3. MisterX for the charge pump idea. Took me a while to get to using it, but I got there eventually.