Hi
I just wanted to update on my experiments with the PP card.
As stated above I was not satisfied with the sound of the stock PP card. Assuming that noise is an issue and that the grounding scheme is a little odd I went to look for hidden potential in the card. As result I have tried and tested an alternative clock connection and different routings for the power supply of the card and clock board.
In chronological order I tried the following:
First I moved the leg of the transformer secondary from the clock board to the PCI card ground at the location of one of the removed capacitors (boy are these components small!). The whole idea is to vastly reduce the return path for currents generated in the secondary.
Soundwise this added some welcome body to the sound and better dynamics. Still the low end lacked power and it all sound a little 'rounded'.
Then I moved the 5V/GND power supply from the PCIe molex directly to the clock board using a molex to SATA psu adapter cable, leaving the Paul Pang supply wires in place. The thought is to have a cleaner ground and 5V for the clock than for the USB cable. This is another big step in the right direction. The whole sound became louder and very musical, natural and organic. Perfect for classical, but unfortunately just not that suited for rock and the like.
Maybe important, but I did not modify the PC PSU molex, so in this setting there is no double 12V/GND routing anymore, only 5V/GND.
This inability to rock motivated me to disconnect the ground wire to the PCI-e card on the clock boards power supply. In the end there is an extra ground path created with this wire connected.
Without this wire only the 5V is connected, supplying to both the clock and the USB cable. Ground for the PCIe is provided by the motherboard.
This experiment was short lived, since now all naturalness and body was gone.
The next step was to disconnect both supplies from the clock board, now there is no 5V anymore. Now clock and PCIe card are fed by separate supplies from the PC PSU and no 5V is available on the USB cable.
This sounded better than the former, more dynamic and fresh. Closer listening learned however that cymbals sounded muted without body and that on crescendos the sound became thin and disorganized. Also, though I am not really good at this, there was no illusion of depth anymore.
FWIW reconnecting only the ground of the 5V to the PCIe, the roundness of the full connection returned.
Now as I feel a little tired with this card-in, card-out business, I switched on my lab supply and fed 5V/GND to the molex of the PCIe. Just as a hunch. Now we're talking! A rich dynamic sound, super musical, fantastic voices, tight bass and forever decaying sounds.
Now whats left to do is to swap the linear supply to the clock board and connect the PC PSU to the PCIe card molex.
Anyway all these experiments support my theories of grounding as well confirm findings of others. Some stuff I took away sofar:
1. there is something with the 5V on the USB lines. It just sounds so much better with the 5V in place. This was already established in the USB cable thread.
2. The clock should have a SEPARATE 5V power supplies from the PC psu to the clock board and PCI-e card. This is the only way to be shure they have a common reference ground. I am inclined to state that only the 5V should be connected at the PCIe cards molex and not the ground, but I did not test that with an extra PSU wire.
Anyway a separate clock supply to avoid ground currents in (loops) in this apparently sensitive area is a great idea from the above findings. This is probably one of the reasons that the DEXA clocks work so well (if they do
).
3. In retrospect the improvement in sound is amazing. For reference I refit my old USB3 card. No chance, a familiar sound but now mechanical, flat, harsh. Not that I ever noticed before! At this moment I can hardly imagine further improvements, but as we believe Nick and Paul, there is a vast potential still waiting!
I hope we can get to the bottom of this USB thing and address it in its root cause. For now this was a great learning experience.
regards, Coen
p.s.: please note that I have been talking about the PP v2 card!
edit: I noticed that my report missed some rationale. Now that only few have read it I have updated.