我把黑膠變檔案

[SGIREM463]

在接觸CAT之前
說什麼我都不會相信我上一篇所說的

Berkeley Audio Alpha USB我曾經試用過
Berkeley Audio Alpha DAC我用過一段很長時間
問題在DAC哪知道哪個是雜訊
哪個該濾哪個不該濾
許多高階DAC有FILTER的功能
我發現FILTER越少越好聽
FILTER太強聲音就呆掉了

還有
我喜歡關掉over- & up-sampling
這些運算常讓聲音變得超不自然

Berkeley Audio 的網站特別強調兩點:


1. 他們輸出段的電源是獨立的, 不是電腦來旳, 想當然爾。

http://www.berkeleyaudiodesign.com/alpha-usb/

Great care was taken in the design of the Alpha USB to isolate the noisy computer/USB environment from the digital audio output. The USB receiver and processing are powered by the computer, while the output master clocks and line drivers are powered by a separate isolated linear power supply. Two key factors combine to achieve the excellent audio performance of the Alpha USB - the unprecedented degree of electrical isolation between the USB input connection and the audio output and the very low noise/low jitter performance of the individually tested audio output master clocks

2. 他們的跟輸出之間有絶佳的雜訉隔離, 用的應該是先進的 isolation transformer, 在這個網頁中有介詔。

http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/15-universal-serial-bus-industry-standard-cables-connectors-and-communications-protocols-between-computers-and-electronic-devices-spdif-converters-shootout-15327/

The 'dirty' and 'clean' sides are both isolated by a chip. The lettering on the chip was removed, but I’m pretty sure this is the ADuM* chip, isolating the I2S lines between the XMOS chip and the SPDIF output.

*The ADuM chips are digital isolators based on the Analog Devices, Inc., iCoupler® technology. Combining high speed CMOS and monolithic transformer technologies, these isolation components provide outstanding performance characteristics superior to alternatives, such as optocouplers.

我剛好有一台 REGA DAC 他們用的也是 isolation transformer,
http://www.rega.co.uk/dac-r-1.html

The USB input stage is comprised of a bit perfect XMOS USB Audio 2.0
with asynchronous clocking. The USB input stage feeds the Optical and
Coaxial input stage via an isolating transformer giving total isolation from
the host computer.

REGA 有不同的的 filters 可以選，這是在隔絕訉源雜訉之後在 Digital Domain 做的調整，照他們説聽感會不一樣, Stereophile review 有一些介紹
http://www.stereophile.com/content/rega-dac-da-processor-page-2