Positive Feedback ISSUE 63
september/october 2012


Addendum to My RMAF 2012 Show Notes
by Lynn Olson


In the aftermath of the show and my essay reflecting on RMAF 2012, here are some additional notes and links for our readers here at Positive Feedback Online.

Lyra Atlas and Frank Schroeder tonearm at the 2012 RMAF show (playing Pink Floyd’s Wish You Were Here). It sounded even better than it looked, which as you can see, was quite beautiful.



This is the link for Peter Ledermann's superb new Hyperion moving-iron cartridge.


Inserted between the CD/DVD transport and DAC, the Behringer SRC2496 also substantially improves the sound of computer audio when inserted between a USB -> S/PDIF converter and the DAC. I highly recommend this inexpensive device for those with large Compact Disc/Red Book collections. Much better value than playing with cables.


With Red Book-sourced content (95% of my music collection), I set the SRC2496 to upsample to 88.2kHz, with Dither ON and added to the 24th-bit LSB. On my system, the difference between dither added to the 16, 20, and 24th-bit LSB is easily audible. This is an indirect indicator that the playback system resolution exceeds 24-bits, or -144dB.

The Monarchy NM24 DAC is the version that supersedes the M24 that I have. From what I can tell, they are very similar. These use the Burr-Brown PCM1704 ladder converter, which is a 24-bit ladder or R2R converter. A 24-bit converter has 16,777,216 possible amplitude values (while the 16-bits of Red Book CD's only has 65,536 possible amplitude values). A ladder converter has 16, 20, or 24 FET switches, and conversion is a one-step process with no digital feedback wrapped around the switch array.


By contrast, the Sigma-Delta converters of most modern DACs typically have 5 bits of FET switches (giving 32 possible values), with the in-between values interpolated through very fast digital feedback (around the switches) and noise-shaping algorithms. In effect, each switch in the 5-bit array is individually pulse-width modulated with sophisticated control algorithms, giving a quasi-analog characteristic from the FET array. As you might imagine, no-feedback flash conversion and feedback-controlled Sigma-Delta converters sound different, and the algorithms in the Sigma-Delta converter makes a big difference as well. (Single-bit converters are no longer used due to inherent mathematical instabilities and clipping in the digital-feedback system. See Malcolm Hawksford at: http://www.essex.ac.uk/csee/research/audio_lab/malcolms_publications.html).

So far, I've been disappointed with the sound of Sigma-Delta converters, even the ones used in highly-reviewed DACs at $5000 and higher price points. The ESS Sabre 9018, though, is different, and according to the engineers I've spoken with at ESS, is free of the problems of the prior generation of Sigma-Delta converters. So I'm curious how the new DACs based on these converters compare to the Monarchy DAC with its Burr-Brown PCM1704 converter.


The Resonessence Concero - USB & S/PDIF ESS Sabre 9018 DAC, and USB to S/PDIF bridge. At this time, 44.1/48/88.2/96/176.4/192 PCM only. High-quality ESS upsampling of 44.1 (Red Book) content is switch-selectable. For user convenience, the DAC supports the Apple remote control for volume control and source selection.

Mytek USB, Firewire, AES/EBU, and S/PDIF ESS Sabre 9018 DAC with 1x (SACD rate) and 2x (studio-grade download) DSD playback, as well as all PCM formats. High-quality ESS upsampling of 44.1 (Red Book) content is switch-selectable. This DAC also has a built-in linestage and attenuator, so it can be directly connected to power amplifiers. For user convenience, the DAC supports the Apple remote control for volume control and source selection.


About Playback Designs: The links below around about the DAC-only version of what I heard at David's place a month ago (the MPS-5 with USB-X interface, which has an excellent optical drive for SACDs). The literature indicates that all sources (PCM and DSD) are upsampled to 2x DSD and run through the proprietary DSD converter. The conversion process is presumably not done with off-the-shelf DAC chips. What I heard at David Robinson's place was in a league of its own; a superb converter.