Mark Levinson No.30.5 Reference digital processor
But 2½ years is a very long time in the rapidly improving digital-processor arena. Since my original review of the No.30 in February 1992 (Vol.15 No.2, p.131), several other processors have challenged the No.30 for supremacy. Indeed, the $4650 Sonic Frontiers SFD-2 bettered the No.30 in many areas of musical reproduction (footnote 1). Nonetheless, it's testimony to the No.30 that it has been universally judged either the state of the art, or a contender for the state of the art, for nearly three years.
The No.30 had seemed such an all-out engineering effort that further improvements would be marginal at best. The No.30's DACs were the finest money could buy (customized UltraAnalog DACs), the power supply was more sophisticated than that seen in any audio product before or since, and the analog output stages represented Madrigal's pinnacle of performance. What could Madrigal Audio Laboratories, designer and manufacturer of the No.30, possibly improve upon?
Despite the fact that the No.30.5the new processor's designationhas the same DACs, the same analog output stages, and the same power supply as the No.30, Madrigal has put the 30 months since the No.30's launch to good use. Most surprisingand even more so after you read my listening impressionsis that the only changes to the No.30 have been in how the digital signals are handled, and in an innovative technique for virtually eliminating clock jitter. The idea that "bits is bits"ie, if the ones and zeros are the same, the sound must be the sameis seriously challenged by even a cursory side-by-side comparison of the Nos.30 and 30.5.
Specifically, the three boards that comprised the digital section of the No.30 have been replaced by a single board in the 30.5. The new four-layer board incorporates the digital input jacks, input-source selection circuits, input receiver, digital filter, and the heart of the No.30.5's new circuitry, the data buffer. Madrigal also substituted two AES/EBU inputs for coaxial (RCA) jacks, and added some other functional refinements. For example, the "aliases" (the names given to different source components that appear in the front-panel display) can now be changed from the outside without taking the unit apart and adjusting tiny DIP switches.
The price has been increased to $15,950. Owners of the No.30 can upgrade for $3000a reasonable price, considering the sonic improvement and extensive changes. This standard upgrade includes a plate that fits over the rear panel to correctly identify the inputs. (If you want a new faceplate that says "No.30.5," you'll have to pay an additional $500, footnote 2) Finally, if you bought a No.30 on or after January 1, 1994, your upgrade to No.30.5 status is free. Fortunately, this upgrade is simply a matter of changing the board in the No.30's center section; the towers and power supply remain the same. Consequently, dealers equipped to service digital products can handle the conversion.
Let's look at each of these changes in more detail.
First, the digital input signals have a shorter and cleaner path to the input receiver than they did in the No.30. In addition, the unselected inputs are completely disconnected from the circuitry by silicon-chip "T" switches that shunt the unselected signals to ground. In the No.30, all input signals were buffered, amplified, and sent to the main pcb, where the desired input was selected. Madrigal discovered that having only one active digital signal inside the chassis improved the sound. In addition, the No.30.5 uses a new pulse transformer with 125MHz bandwidth, compared to the 25MHz transformers used in the No.30.
The NPC 5803 digital filter in the No.30 has been replaced with the new NPC 5842 filter chip. The 5842 will pass up to 24-bit words, in contrast to the 18-bit maximum word length possible with the 5803 (footnote 3). In addition, the 5842 is controlled by a DSP chip to ramp the volume up and down when switching between inputs. (This volume-ramping function was performed internally in the 5803 filter used in the No.30.) The DSP also turns off the 5842's internal dither.
The No.30.5 also benefits from what Madrigal has learned about digital power supplies. The digital board's regulation is distributed differently to reduce jitter.
By far the most important change to the No.30 is the innovative and elaborate jitter-reduction circuit. In most processors, including the No.30, the input receiver recovers the clock from the S/PDIF datastream, which becomes the master clock for the processor. Any jitter in the datastream, and any jitter intrinsic to the receiver, ends up at the DAC's word clock, where it degrades sound quality.
Footnote 1: I've received conflicting feedback over my opinion of the SFD-2. Some with ears I trust told me that my review was too conservative, and that the SFD-2 is far better than the No.30. Others maintain that the SFD-2's overly forward perspective precludes it from beating the No.30no matter what its other attributes.
Footnote 2: I was reminded of how much more expensive everything is these days while reading Rider magazine: A 1995 Honda Gold Wing touring motorcycle (fully loaded) is up to a whopping $16,799.
Footnote 3: This is a very important feature if you have a 20-bit data source (such as a Nagra D digital recorder). At the Stereophile Hi-Fi Show in Miami this past April, attendees were treated to Peter McGrath's 20-bit master tapes played through a Nagra D and the No.30.5.