Here are some notes I was sending to bryman79 but his box was full. He had asked about using another board, if you could test the code before committing to a board, the use of 80Mhz or 125Mhz instead of 77.76. By the way, I didn't note below but the best ADC clock frequency is the one available up around 122.88 because of the extended harmonic relationship. I've been trying to purchase one but they aren't available in small quantities.
1) code, instructions, etc are built around the 605 eval. I don't know anyone that has tried to convert it to another board.
2) A lot of the code actually runs in the PC, fully editable. The FPGA is used for capture mostly. All source is available.
3) Andrew's code that runs on the PC can be executed you just won't be able to load the FPGA or get any value from it, just a blank graph.
4) It is very important to minimize the harmonic relationship between the ADC clock, DUTs and references. So using a 77.76 produces a spur that is like the 59th harmonic of one of the clocks. If you used an 80Mhz AdC clock, and measured a 10Mhz DUT, you would have a large spur at the multiples of 8hz. You need to minimize the mathematical relationship between the ADC clock, the reference and the DUT because even the 59th harmonic can be seen at the levels we are hitting.
With dual references and the later setup using connectorized components, we are getting noise floors below -180dB. If you get the setup running, send me your email as Andrew, Pawel, Adrian and I have a lot of threads on power supply grid noise reduction, use of dual refs, what splitters to use (we are back to non-resistive), anti-alias filters (Adrian is the brains of the outfit and he isn't running filters now). Don't both with Andrews splitter/amps. I built them before we knew better. The splitters and filters are ok, but the choice of amp chip could have been better.
Adrian uses a different setup for his ADC clock but I don't know if it was proven to be worth it. Andrew, Pawel and I use a small power supply with the LDO low noise regulator and a capacitive multiplier being fed in my case from a "lab grade" (right) Tektronix supply. I finally used Dewalt 20V batteries into a 15V or appropriate regulator board for the test once I warmed everything up with a power supply. This eliminated the power line (grid) noise and harmonics. So plan to run the tests on batteries for everything. Tests run up to 10hours with diminishing returns after an hour but worth the longer run. The system performs far better than any DUT I have, many of which have very good PN below -170dB.
If you plan to use power supplies, build the circuit by Jim Williams in AN83 to test your supplies. Adrian and I built one using an ssm2019 but I never got good results with that chip and the circuit in AN83 is well thought out. Or just use batteries but you might find they inject a lot of noise (the rechargeables do).
You will need two low-noise references and I wouldn't bother with anything other than the Wenzel 501 series that have the datasheet available with PN below -165 at 10khz. We have been scarfing them up on ebay like vultures for less than $70 shipped in the US. You will then need to use shielded power runs with about 10,000uf right at the oscillators power pins, both the refs and DUTs. You also have to isolate the system magnetically away from transformers, etc by at least a meter. I ended up having some noise on my neutral wire that contributed to my decision to move to batteries.
Adding to the notes above, we ultimately got better results with two references, without filters, using non-resistive splitters on the DUT, with heavy capacitance all around, isolated from transformers. We also found that amplifying the DUT and references and then bringing them down with high-quality fixed attenuators, or the variable Weischel(sic) attenuators, keeping the input above 95% as measured with Andrews code, produced the best results. Adrian, who continues to be a very, very patient person, was helpful beyond any reasonable expectation. He hit a noise flow below -180 but has very, very good references.
That's about all for now. Let me know if you get the 605 board and build it out. Very, very high-end results for very little money, comparatively. I know people that spent 10x as much for nowhere near the results.
Jerry