اینم داره به جمع سیستم من اضافه میشه ، دلیلش اینه EAR DAC 4 ورودی USB رو به خوبی SPDIF پخش نمیکنه و با پیشنهاد خود Gordon که ایشون تو طراحی همین Alpha USB نقش داشت تصمیم گرفتم این USB to SPDIF Converter رو بیارم .
The final production version of the Alpha USB contains dual fixed oscillators. One for each sample rate family of 44.1, 88.2, 176.4 kHz and 48, 96, 192 kHz. Only a single oscillator is operational at a time. Even very good low jitter oscillators can produce relatively high levels of low frequency phase noise.
Adding to the Alpha USB’s excellent clocking is the use of Streamlength<sup>™</sup> asynchronous USB code in conjunction with the XMOS USB receiving chip. Small companies such as Berkeley Audio Design need to leverage design talent. In this case there was no reason to reinvent the wheel. The Streamlength code was selected because it was already well developed and was very robust. Streamlength asynchronous USB code controls the data flow from the computer or music server and the newly developed crystal oscillators take control as the master clock generators. No matter what one believes about the importance, or lack thereof, of asynchronous USB and its oscillator design “requirements” it would be hard to second guess the Alpha USB’s design approach.
Another major contributing factor to isolation is how the USB interface is powered. Berkeley Audio Design elected to power the USB receiving chip in the Alpha USB via USB bus power from the computer. Power emanating from the computer’s USB port doesn’t traverse any further than the USB receiving chip inside the Alpha USB. ‘Berkeley’ uses its proprietary isolation techniques that are said to provide much better performance than traditional opto-isolation methods while keeping computer generated noise away from the sensitive output clocking and driver circuitry. Powering the audio output side of the Alpha USB is a low noise linear power supply. This noise filtered linear supply feeds clean power to the oscillators and the digital audio output circuitry.
https://www.computeraudiophile.com/ca/reviews/Berkeley-Audio-Design-Alpha-USB-Review/
ست نهایی این میشه :
Macbook pro 2014 USB 3.0 -> Berkeley Alpha USB -> EAR DAC 4 (BNC input) -> EAR HP4 Headphone Amplifier (XLR input) -> Sennheiser HD800
All Cabling : Purist audio
