Yeah, I think the chips and circuit design are so good the performance is confined to a very narrow envelope, with very little room for tweaking. In a word, excellent.
But then part of the fun of diy is discovering circuit behaviour and playing with it.....right ?
So far, my 'best' tweak is filtering the usb power with a pi filter of 1uF x7r - 100uH 5amp toroid - 1uF X7R. This has a corner frequency of around 15Khz so it seems to work where the onboard regs are less effective and provide a bit of a cleaner supply way up into the Mhz region.
One thing I'm wondering about on the y1 usb board, would be the effect, if any of swapping the position of c10u and r4u. If I did this then it would be easier to implement the pi filter. R4u would become a 1uF ceramic and vbus could be connected to VCC via the toroid and the second 1uF ceramic could go across VCC to gnd.
What do you reckon ?
BTW, I'm pairing the Y1 usb as the i2s source for a y2.
EDIT : the change would make L2u and r4u into an lr low pass filter - 3.2x10^-11 H and 47k R = no effect, but would it affect U2U or the host pin ? I assume not....