Can you ABX different filters? I think so.
1) Level matching is important. We see with the Benchmark DAC3/AHB2 combo that higher DAC level voltage can help lower amplifier gain work together for better results. So older CD players that juiced the voltage could have genuinely sounded better.
2) The nice thing about modifying the audible signal is when you have full control over it. The Marantz SA-11s2 has a mode that introduces distortion that probably acts as a mask to decrease the subjective high frequencies which works great with poorly mastered CDs. It shouldn’t work, but it works. Critically, it’s fully optional.
Denon Alpha helps undithered vintage CDs sound better on the small window of time in the early CD era. See Filter 2. Looks horrible. This for a product that also boasts channel separation “better than 130dB in both directions below 800Hz, and a still superb 107dB at 20kHz.” By comparison, the Mola Mola Tamabaqui “Channel separation was 112dB in both directions across the audioband.” So you have something with certain spectacular measurements that also lets you distort the sound to preference.
Sidebar 3: Measurements The Marantz SA-11S2 Reference was assessed using Audio Precision's SYS2722 system (see www.ap.com and "As We See It" in the January 2008 issue), as well as, for some tests, our Audio Precision System One and Miller Audio Research Jitter Analyzer.
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