Hi just to add my usual trivial thought
i think that the bigger effort should be done to get a very clean source signal.
This signal is the end what will be amplified by the following amp stages. Trivial i know ...
IMH experience if the source is very good almost any decent amp/speakers combination can sound at least satisfying.
Just an example.
I had a bad sounding cd player. After substituting other components just out of curiosity i put a plastic turntable with a cheap Nad phono stage in place of the cd player.
I was amazed how much more musical the whole system was sounding ... i am sincere.
So the real problem impacting the whole performance was not the system but the source.
These days i am committed to get a "musical" digital sound out of wav files using a pc.
I can tell you that this is not that easy at all. Just a detail can ruin the whole picture.
In my opinion the usb to spdif converters can be key units to build up a nice sounding system with almost any pcs.
If the spdif signal out of them is good quality than any decent dac will do the rest. And even cheap decent dacs can be found.
Speaking of the U12 i think i have solved the usb port issue with an external usb power supply in a decent way.
Now i have still some issues open:
1) usb cable quality (i could have jitter in the usb transmission)
2) filtering of the mains entering the U12.
Regarding point 1) i am trying different solution for the usb cable (for instance taking out ferrites could improve the sound).
Regarding point 2) after a lot of thinking, given that, as someone rightly has pointed out, the current drawn by the U12 is very very little (around 0.1 A max ?)
i would really like to try the " chokes " solution, because the common EMI filters are specified for much higher currents and could not be that effective with smaller currents (
)
I see many cheap chokes on ebay but i have no clue of:
1) which model to buy
2) how to connect it to get a nice mains noise filtering upstream the toroidal.
I see chokes used often also in dvd player and other digital players.
Could someone direct me to some pages explaining how to wire these chokes ?
Thanks a lot indeed for all the very very interesting disclosing of tech advice.
Kind regards, gino