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DSD vs PCM 24/32 Comparison with Mojo2 (Part 1)

I have been working on a new reference based exclusively on the Mojo2 DAC in combination with PUREDC 5V power inside a RFSTOP Faraday Box. I use optical signal transport from my source (Windows laptop) and RFSTOP Signal SE filtering to headphones. PCM 16fS was to be my exclusive test stream but the recent release of PGGB 6.0 with DSD mastering has created quite a stir on forums and I decided to do a proper DSD/PCM comparison. And while I was at it, I decided to test if PCM 24-bit vs 32-bit was audible.

On the topic of sampling bit-depth, PGGB content at 32-bits has a lower inherent noise floor than 24-bits and this is translated to the Mojo2's WTA 2/3 using the excellent noise shaping of Rob Watts' design. Inside the Mojo2 4e Pulse Array (multi-bits-to-volts), the aggregate input energy might be retained but I had my doubts that the amplification stage could resolve any audible benefit of 32-bit content. Similarly, with DSD input, I presumed that Mojo2 would do an excellent job of preserving MHz frequency single-bit energy but I believed (as Rob himself has stated) that Chord DACs are optimized PCM DACs.

 My PGGB test suite was 20 albums mastered in 3 different ways:

  1. PCM 24-bits @ 16fS
  2. PCM 32-bits @ 16fS
  3. DSD256 @ 48kHz fS sampling (to maximize temporal resolution)

Other PGGB settings were at defaults at MAX precision. DSD was limited to DSD256 supported by Mojo2. I wanted to test both using filtered USB-C active optical cable as well as SRCDX + OPTODX; My initial tests were performed using USB-C to avoid any beneficial impact of DBNC. The results may surprise you. Stay tuned for Part 2!

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