@rikardo: 9V is borderline too much.
Régulation faible bruit de l'alimentation permettant une alimentation de 6 à 9 VDC (2A)
I bet this is a low-dropout, low noise regulator. I can guess what kind. You are not doing yourself any favors operating at or above 9V.
9V is the upper limit for the Audiophonics board, and allowing for line and load regulation on a linear supply, you will be exceeding 9V during normal operation. If you can, you should measure it with a multi-meter, and adjust down as much as possible, perhaps to around 7~8V.
The Pi will draw less than 1A while running, perhaps as low as 0.5A. Linear supplies get their "clean" power in part by not using "noisy" regulators. Downside is poor load and line reg, which does not matter at all (for audio), unless you are close to a limit. Drawing 0.5A from a supply intended for ten times that current could give you well over 9V at the supply input to the regulator on the DAC board. Even if not, the regulator is being unnecessarily stressed.
The load regulation is an inverse relationship. Low current as % of maximum == high voltage. Load current close to maximum == low voltage.
@[deleted]: You need 6V
absolute minimum. The regulator on your DAC uses the difference between 5V and 6V to provide clean power for the D/A conversion, and extra power for the Pi and any dongles. Less than 6V, and you may as well buy the cheapest DAC you can find on ebay and call it a day.
The six volt supply is critical to get what you paid for when you bought this DAC! I cannot stress this enough.
