Mark,
Like Ric I made my own cable, I used about 6" of pure silver wire, I then slid some tinned shield over this and soldered two grounding wires on the shield. I then wrapped all the in teflon tape. Direction is very important so you need to experiment which direction it is obvious which is better.
I used a abracon OCXO AOCJY1 100mHZ clock, no need for the 106 clock as the gustard is not native 48K capable at 512, it down samples to 44K levels. Look at the LKS 003 thread on head fi around P16 b0bb shows what he did. (Note this requires an external PSU and high speed regulator, as a OCXO demands much more amperage than a normal none OCXO clock). Since the clock is dip14 I soldered some very short wires to a dip 14 socket and now can swap dip 14 clocks at will. The Abracon is about $65, cheaper than a pulsar, but not as good, but better than the crystek or accusilicon which Gustard uses. The clock mod replaces the coax cable, I have a picture on head fi of my clock installed (maybe without the dip14 socket), but with an ohm meter pretty easy to figure out what pads are signal and ground for the clock, and the power for the abracon would come from an external PSU. Only 3 of the 4 pins on the clock are used (signal, ground and power)
Bottom of boards are just solder no components. No I did not play with those diodes you mention, thought about it but at 512 music is so good I hate to put the dac on the bench.
I build my own PC's for streaming a i7-6700K or even 7700K would run about $1000 parts cost for a decent machine, not the SMG $16K server level but quit adaquate. I have built 5 audio PC's so far, learn something on every build. Connect direct to dac with USB they will work as dac's come and go. Good investment.
Like Ric I made my own cable, I used about 6" of pure silver wire, I then slid some tinned shield over this and soldered two grounding wires on the shield. I then wrapped all the in teflon tape. Direction is very important so you need to experiment which direction it is obvious which is better.
I used a abracon OCXO AOCJY1 100mHZ clock, no need for the 106 clock as the gustard is not native 48K capable at 512, it down samples to 44K levels. Look at the LKS 003 thread on head fi around P16 b0bb shows what he did. (Note this requires an external PSU and high speed regulator, as a OCXO demands much more amperage than a normal none OCXO clock). Since the clock is dip14 I soldered some very short wires to a dip 14 socket and now can swap dip 14 clocks at will. The Abracon is about $65, cheaper than a pulsar, but not as good, but better than the crystek or accusilicon which Gustard uses. The clock mod replaces the coax cable, I have a picture on head fi of my clock installed (maybe without the dip14 socket), but with an ohm meter pretty easy to figure out what pads are signal and ground for the clock, and the power for the abracon would come from an external PSU. Only 3 of the 4 pins on the clock are used (signal, ground and power)
Bottom of boards are just solder no components. No I did not play with those diodes you mention, thought about it but at 512 music is so good I hate to put the dac on the bench.
I build my own PC's for streaming a i7-6700K or even 7700K would run about $1000 parts cost for a decent machine, not the SMG $16K server level but quit adaquate. I have built 5 audio PC's so far, learn something on every build. Connect direct to dac with USB they will work as dac's come and go. Good investment.
I have read through every X20 thread on every site I could find and probably have lost track of it all. I wish there were more people exploring new mods, trying them out and reporting back. Maybe diyAudio is the place for that.
What high-grade microwave coax did you use for the 100 MHz. clock?
What clock board? Link (besides the $400 Pulsar!)? Instructions anywhere for installing one?
Is a 106.25 MHz clock (instead of 100 MHz) worth a try to better handle DSD512?
Are there any components on the bottom of the DAC/buffer board? I've not needed to take mine out yet and it seems like there ought to be more/bigger bypass caps around the DAC chips.
Have you noticed / replaced the M4 diodes (D12, D13, D14, D15, D26, D27, D28, D29) on the edges of the DAC/buffer board down by the output buffers? Are they worth replacing with SMT Schottkys? Yeah, I know Lindahl transformers are the way to go, but these might be polluting power rails if on them.
I've resisted getting into the whole music server and software thing because it sounds like a longer crazier journey than soldering iron mods. $15K for a tweaked PC from Monaco? I'm also trying to be rational on investment when new DACs and CPUs come out all the time (like the i7-7700 due out this quarter). I'd like to be able to take out a $400 clock and Lindahl transformers if I put them in my X20 and use them in some future ES9038 DAC, without ruining the X20. As of now my tab is only about $20 inside and $100 for a AQ power cord.
Another challenge is the DAC sounding so good that I end up listening to it instead of putting it back on my bench! If I had a second one to leave playing while working on mods, I'd probably still get distracted by the music.
BTW, I'll try to attach a pic of my back panel which shows my mounting of the transformers using 1/4"x2" nylon bolts, nylon fender washer, and 1/8" thick rubber washer. No metal in there with two corrugated cardboard and the supplied thin rubber disk under the transformer.