C Hing,
CAST 與 Krell 的 current drive 差不多, 一定要硬件的輸入和輸出都有CAST插, 比RCA 高幾班!
例如由DAC Cast out 去Pre-amp Cast in -> Pre-amp Cast out 去Power amp Cast in. 根據Audio-Gd 何老師解釋用Cast 音質最純和最傳真!
Once I bought my 1st Audio-Gd product the FUN DAC/headphone amp over 2 years ago, I love it!
As you mentioned, the cost/performance ratio is very high and reliability is very good too.
Sound produced by my Audio-Gd gears is of very good resolution, stable sound stage, very good dynamics (particularly when playing piano and violin sources), vocal is neutral and bass is solid and deep, but sometimes I may prefer the upper freq less aggressive.