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Some info on the Marantz SA11S1 DSP & DAC

Posted by PS Yeo (A) on December 10, 2007 at 19:17:29

In Reply to: Marantz SA-11S1: Upsampling? Oversampling? Does it matter? posted by FidPup on December 10, 2007 at 12:09:04:

Hello,

I own the Marantz SA11S1 as well the service manual, and may be able to answer some of your questions. BTW I am an R&D EE for 17 years in trade.

1. DAC
The SA11S1, SA11S2, SA7S1 all employs the NPC SM5866 DAC. The unique thing about this CMOS 24-bit Sigma Delta DAC is that it DOES NOT integrate in with an oversampling FIR digital for the PCM data, unlike the other popular competitive designs such as the AD1955, PCM1794, DSD1792 types etc. An external digital filter (Either a CMOS VLSI or DSP type ) is required for the PCM data input. In some point the SM5866 is equivalent to the popular and expensive R-2R type PCM1704, where both required external digital filter to operate unless you want to have an NOS design, which is possible.

However the SM5866 does come with a switch-able FIR filter for the relative noisy DSD data stream. Once engaged it will filter the 100 KHz quantization noise inherited from the DSD data. Two filter slopes are provided and you can select them from remote or simply just bypass the 100 KHz digital filter for the DSD, a neat design from Marantz.

2. Digital Filter
Marantz employed a Motorola (now call Free-Scale Semiconductor) DSP56364 with external Flash memory to perform the role of traditional oversampling / interpolation FIR digital filter. There is no ASRC such as the AD1896 / SRC4192 types upsampling here, which is a good thing for me at least , where I am not a fan for the now ever popular and overly used ASRC. (No Flames please !!). In some extends the SA11S1/S2, SA7S1 is like the products from Wadia, older Krell and Theta products where custom DSP digital filter algorithms were /are employed.

The DSP run in good old tradition 8 x oversampling mode at 352.8 KHz. Three Filter algorithms were provided and selectable form the remote control. The First two Digital filter settings are Wadia alike and optimized for Time domain response, with minimum ringing and echoes, thus slow row off at 20 KHz at about 1-2 dB. These two settings provide the best soundstage depth and three dimensional performance, IMHO.

The third Digital filter setting emulates the very successful Philips SAA7220 4-times oversampling digital filter but run in 8-times OS 24 bits mode. The frequency response is maximum Flat which adhere to the traditional old school thinking FIR design. This Digital filter was first developed in 1999 for the Marantz Classic CD-7 in order to replace the discontinued SAA7220.
For those people whom missed the good old late 80s 16 bits four-times oversampling or the early 90s 20 bits Eight-times oversampling; this is the definite option. This setting provide the best dynamic range and bass response, but flat 2D soundstage, IMHO.

Hope these may clear some doubts on the SA11S1.
Well subjective Sonics aside, I would still rate the SA11S1, and the newer SA11S2, SA7S1 one of the best buy in current digital audio gears. It come with superb built, DSP based selectable Digital filters, no ASRC, and reasonable pricings.
Too bad Marantz did not elaborate on its competent DSP digital filter Engineering and market it well such as Wadia, else it may sell a lot more machines than now. I only discovered its Design / Engineering strength after I got the machine and later, the service manual.

Regards
Max Yeo PS

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