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Reviewer: Paul Candy
Source: Rotel RCD-971, CEC TL53Z [in for review[, Audio Zone DAC-1, Pro-Ject RPM 5 turntable, Pro-Ject Speed Box, Ortofon Rondo Blue cartridge
Preamp/Integrated: Manley Labs Shrimp, Audio Zone AMP-1, Audio Zone AMP-D-1 monos [in for review], Pro-Ject Tube Box phono stage
Amp: Manley Labs Mahi monoblocks
Speakers: Green Mountain Audio Callisto (on sand filled Skylan stands), Hornshoppe Horns, AV123 Strata Minis, Mark & Daniel Aragorn [in for review], (2) REL Q108 Mk II subwoofers
Cables: SilverFi interconnects, Auditorium 23 speaker cables, Stereovox XV2 digital
Power Cables: Audience powerChord, Harmonic Technology AC-10 Fantasy.
Stands: Grand Prix Audio Monaco four-tier rack.
Powerline conditioning: BPT Pure Power Center w/Wattgate 381 outlets, Bybee Quantum Purifiers and ERS cloth, GutWire MaxCon, Blue Circle BC86
Sundry accessories: Grand Prix Audio Apex footers, Isoclean fuses, Caig Pro Gold, Auric Illuminator, Audio Magic/Quantum Physics Noise Disruptors, dedicated AC line with Wattgate 381 outlet, Echo Busters acoustic room treatments
Room size: 11' x 18' x 8', long wall setup, hardwood floors with large area rug
Review component retail: $995 for stock unit; $695 for Stage Three Mod

PS Audio was born back in 1974 when Stan Warren (the 'S' in PS Audio) showed up at Paul McGowan's door (the 'P' in PS Audio) with $500 in hand for what, unbeknownst to Paul, would become Stan's half of their new company. Their first product was a well received $59.95 phono preamp. Building upon that initial success, other components like preamps and power amps were introduced and depending on whose version
of history you believe, also the first commercially available standalone audiophile DAC, the Digital Link. Successive digital products followed with the Ultralink DAC and Lambda transport, arguably among the most successful and well known digital products of their day. One of the architects of the original Digital Link, Rick Cullen, remains associated with PS Audio to this day via his firm Cullen Circuits which has been the primary builder and design consultant for all PS Audio products since 1990. Cullen has also subcontracted for other well-known audio firms such as Camelot, Amplifier Technologies (ATI), James Bongiorno's Ampzilla, Arnie Nudell's Infinity and Genesis Technologies. Cullen also offers his own line of attractively priced ICE powered amps under the Wyred4Sound brand.
Sidebar I - High end audio and modding according to Rick: "Well, I have been involved in this field of audio and high-end for most of my life. In fact, 35 years worth! I think that's a lot of time learning and working on products and this cumulative experience has taught me a great many things about the industry and our goals and what makes for a good product to work on. First off, knowing if I succeeded or not is easy because the proof is in the pudding as they say. I listen and I listen to everything I do. It's a constant challenge to relate the electronic changes..." continue

For today's review, we have PS Audio's latest DAC, the Digital Link III, and the same unit modified by Cullen Circuits to their Stage Three level. Before we get to the mod, let's look under the hood of the stock version first: The DL III features Cirrus Logic's new low-jitter CS8416 receiver, Texas Instruments' (formerly Burr-Brown) new SRC4192 sample rate converter which upsamples to 96 or 192kHz and TI's 24-bit/192kHz PCM1798DB processor which boasts a 123dB dynamic range, 0.0005% THD, an 8 times oversampling filter and differential outputs.

There is much confusion and disagreement about the alleged merits and even the very definition of upsampling. As far as I understand it, neither process creates more information; you can't get 24-bits from a CD. Oversampling uses integer multiples of the original 44.1 kHz signal (i.e. 88.2, 176.4 kHz etc) to shift digital distortion and noise further out of the audio band to allow for a shallower digital filter with less phase shift and ultrasonic ringing. Upsampling occurs prior to oversampling and utilizes non-integer multiples of the 44.1 Hz source rate (i.e. 96, 192kHz etc). This process supposedly enhances jitter rejection and the processing accuracy of the 16 bits on the CD.

While many folks tend to focus on the processor specs or sample rate conversion process, the reality is that much of a CD player/DAC's sonic performance is dependant on the I/V and output stages which are usually designed around op-amps. While op-amps in many applications can be very successful, many also consider them sonically problematic for digital gear. According to PS Audio, "the greatest opportunity for a bright and edgy digital sound is caused by op-amp based current-to-voltage converters (I/V converters) because the high speed of the DAC's output causes transient or slewing induced distortion in the op-amps (SID). SID is a combination of feedback and transient response issues that some exotic high-speed op-amps can come close to handling but all have a problem with nonetheless."

The DL III sidesteps the slewing problem by eliminating the I/V stage's feedback via a unique single transistor I/V converter that cannot slew. This circuit has open loop gain, low distortion and high linearity to supposedly eliminate the traditional bright edgy sound many listeners associate with digital. Instead of a gain stage with active feedback filtering, a simple passive first-order filter hands off to a discrete (no op-amps) class A zero-feedback FET/bipolar input/output stage. Again, this eliminates feedback and speed issues.

Incidentally, if you think you are getting around the potential crappy sound of op-amps by buying players/DACs with so-called tube output stages, think again. Most are nothing more than clever marketing i.e. a pair of tubes stuck to the outputs of op-amps. You still get the problems of op-amps just with a little tube flavor to hopefully mask their limitations. If you want a true tube DAC/CD player, my advice is to ensure that it has a pure tube output stage sans op-amps.

Everything here is direct coupled, i.e. no reactive components are in the signal path from DAC output to analog output. A look under the hood shows considerable use of tiny surface-mount devices (SMDs) which have many advantages over traditional through-hole components. See here for an overview.

The power supply features a large toroidal transformer, 48,000uF of filtering, Linear Technologies LM317 voltage regulators and high-speed, low-noise diodes. The rear panel carries a pair each of RCA and XLR analog outputs plus S/PDIF, toslink and USB digital inputs, an IEC power inlet and power switch. A small push button on the front right side switches between 96 and 192kHz sampling rates.
Three adjacent LEDs indicate digital lock and sampling rate. Another push button on the left toggles through the three digital inputs. In default mode, the DL III will automatically lock to the first digital signal it detects. It will also shut down to standby mode (which turns off the LEDs and mutes outputs) if the signal is lost or the transport is powered down. Pressing the input selector button while the unit is powered up turns off this feature. Pressing and holding the same button for two seconds will reactivate it.