derSammler wrote on 2020-03-07, 15:13:
That shouldn't happen. I guess while there is a diode on the USB's 5V line, they forgot one on the wavetable connector..?
That is correct, on X2, there's a diode on the USB 5V line, but not on wavetable 5V pin on X2 side.
You would expect it on the soundcard, but apparently not.
For X2 design decision : --> The original idea was you could power an arduino shield with X2, completely from USB, and this works nicely :
I was planning to make full arduino based midi module with display and keys and ... powered over usb -- a bit like MB32 idea
But except for my own experiments, I think nobody uses X2 this way.
If both systems are powered, the PC 5V will normally be higher than usb voltage minus diode drop, so no current will flow.
I did this many times without problem. (but both were powered). But when PC is powered off, and usb coming from somewhere else, this is indeed a possible side effect (depending on the soundcard) !
well ... to avoid any issue or strange effect, it is recommended to remove X2 for USB updating.
On the upcoming new batch X2E : X2 Extended (currently have working prototypes, production batch in a few months),
i already added this diode for added safety , and some other minor changes (same capabilities as original X2)
For normal use, X2E will be exactly the same as X2 And if needed for arduino, the diode can be bridged.
Have a look at the X2E photo, you see D1 and D3 : 2 diodes instead of 1.
Visit http://www.serdashop.com for retro sound cards, video converters, ...
DreamBlaster X2, S2, S2P, HDD Clicker, ... many projects !
New X2GS SE & X16GS sound card : https://www.serdashop.com/X2GS-SE ,
Thanks for your support !