OliverD wrote:I have recently stumbled upon 2 weird problems with my trusty y2 (pic). As you can see in the picture, I am also using an e24 power switch circuit. This is the root of my first problem:
Ever since permanently hooking it up to my pc and the b22/symasym chain of preamp/poweramp, it was hard to switch it on after turning the power an from the outlet it was plugged into. It switched off immediately once I let go of the switch for 2-3 times sometimes more, before eventually deciding to stay on, while producing a loud screeching noise in the preamp/poweramp chain regardless of whether the input was active or not. Some sort of DC offset i suppose?
This problem led me to alter the y2 to never use power from USB through bridging pin 1 and 2 on J2D, which in turn led to the second weird problem:
Now the screeching high pitched noise appears anytime the power from the y2 DAC is not turned on, it immediately vanishes once I turn it on. This probably means the screeching noise described above was produced while the y2 was switching from USB to external power. This modification didn't help with the turn on problems though. It still sometimes take 2-3 tries to turn it on.
amb wrote:So the ε24 works fine when the preamp/poweramp isn't connected? Please double check to make sure all the resistor and capacitor values used on the ε24 are correct? And you used the correct MOSFET?
The screeching noise occurs even when the preamp is switched to a different input? Can you characterize the screech? Is it just a burst of noise that stops, or is it a continuous noise?
I think your screeching noise may be due to a ground loop. Does it screech when the USB cable is disconnected from the computer (but the DAC is on)?
amb wrote:In order to truly disable USB power (except for host detect), you not only should jumper J2D 1-2, but you should also remove U1D. Otherwise, U1D may "fight" itself when its output voltage isn't what it's supposed to be.
OliverD wrote:I have recently found the time to analyze the noise problem and it seems to be a problem with my special configuration of connecting the ground of the y2 to its Box enclosure and through the mounting screws connecting it to the power supply ground of the surrounding enclosure.
Can I wire the TORX147PL from my main enclosure to the y2 board instead of mounting it on the board if I keep the wires short (e.g. 1-2 inches max)?
And a little off topic as well:
@LinuxWorks: I have seen you using 1-pin sockets for exchangable resistors in the d1/d2 threads iirc. Do you have a mouser article # at hand? I couldn't find the one you used and any hint would be greatly appreciated. I am currently building a phono stage and would like to keep the gain easily exchangeable to accomodate MC and MM cartridges.
amb wrote:You can try to isolate the two enclosures from each other...
OliverD wrote:For a perfect isolation I need to get the correct (isolating) mounting screws (the y2 enclosures hangs on the backpanel inside the PSU enclosure)
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