Aesthetix Pandora

Saturn Series Tube DAC

The Aesthetix Pandora is a vacuum tube based digital-to-analog converter with one USB and three SPDIF inputs that has become a favourite among the audiophile community because of its exceptional sound quality. High quality construction techniques include an all-aluminium chassis, stainless steel faraday cage to isolate digital sections, multiple power transformers in a stainless steel enclosure, and multiple regulation stages.

The Pandora USB solution uses the asynchronous transfer mode licensed from Gordon Rankin / Wavelength Technologies with an ultra-low jitter fixed-frequency crystal clock immediately adjacent to the DAC. This technology allows for jitter levels over one hundred times lower than previous USB solutions. USB is capable of Class 1 audio up to 96KHz / 24bit and Class 2 audio up to 192KHz / 24bit. SPDIF/AES inputs use a unique jitter reduction technology that offers jitter performance on par with asynchronous USB and are also capable of up to 192KHz / 24 bit.

To combat computer generated noise pollution, Aesthetix have designed in optical couplers that galvanically isolate the USB input and processing sections from the DSP section, including ground. There is no continuity between any part of the USB input and any part of the Pandora digital or analog sections. While expensive and difficult to do, it achieves a huge sound quality improvement over a directly connected USB section that allows noise to infiltrate the audio circuitry.

The DSP section utilises the Motorola DSP 56362 for their specially designed oversampling filters, which adapt according to the incoming sample rate. Over 1.5 megabytes of static memory buffering is selectively used to completely isolate incoming data from USB and SPDIF from outgoing data to the DAC.

The clock section of a digital product is absolutely critical for audio performance. Any jitter (tiny timing variations) or noise will cause the DAC device to perform analog conversions at incorrect and varying rates, causing clearly audible negative effects. The easiest timing solution (but also the most jitter prone) is to simply allow the DAC to use the clock of the incoming source device. A slightly better solution is to incorporate an internal clock at the DAC using an off the shelf crystal oscillator to regulate the timing. The Pandora takes this a step further by utilising specially manufactured crystal oscillators custom cut to their exacting specifications. These crystals offer radically lower jitter and noise than any standard issue part. There are separate crystals for 44.1KHz based sources (44.1, 88.2, 176.4KHz) and 48KHz based sources (49, 96, 192KHz). The clock section is powered by its own discretely regulated power supply, to isolate it from the DAC.

Digital to analog conversion is performed by the Burr-Brown PCM 1792A run in pure differential mode. Differential mode is a critical implementation feature that only amplifies the audio signal itself, cancelling noise and other digital artifacts. The digital side is isolated from the analog side, with discretely regulated separate power supplies for each. Special attention is given to circuit layout and component selection.

The Aesthetix reputation for state-of-the-art analog stages is continued in the Pandora, which features a current-sourced fully differential zero feedback vacuum tube amplifier (12AX7) being fed from the DAC. Differential amplifiers have the unique ability of rejecting “common mode” signals, particularly useful in digital audio products, where high speed clocks and other digital noise can disrupt the delicate analog circuitry. Both the Pandora and Romulus feature Rel-Cap polypropylene coupling capacitors and Roederstein metal film resistors. Ground noise is reduced by using two separate discretely regulated positive and negative power supplies for the voltage gain section.

Output buffering is performed by one 6922 per channel, also run in pure differential mode with zero feedback. This is a unique configuration, providing much of the benefit of balanced operation for single-ended outputs. The output section also has separate discretely regulated positive and negative supplies which are completely isolated from the voltage gain power supplies.

As with every Aesthetix product, the Pandora power supplies received tremendous attention. If a single transformer is used to supply all the necessary voltages and currents in a product, digital noise is allowed to easily traverse the transformer windings through stray capacitance and pollute the delicate analog sections. Separate windings help, but only a little. The real solution is separate transformers, where no interaction can occur between windings. The Pandora digital / DSP section is given its own transformer and regulated power supply. Individual digital sections are further locally regulated to isolate them from each other. An additional transformer and dedicated regulator are used just for the control system. A further special transformer is custom manufactured for Aesthetix for the analog sections, where six separate windings and regulation stages are used for the critical functions described above.

All of this attention to detail has resulted in a DAC that transcends what is normally expected from an audiophile piece of equipment. The Pandora scales heights that are normally the realm of uber-expensive multiple chassis DAC products and it does it with ease. Sound quality is the prime objective here and the Pandora is a phenomenal achievement.

Options

The Pandora is available with an optional High Resolution Volume Control. A high resolution relay-based volume control may be added to the Pandora, allowing the unit to directly drive a power amplifier, ideal for many systems. The volume control for Pandora and Romulus is very special. Typical digital products control volume entirely in the digital domain, where every 6dB of volume attenuation causes a loss of 1 bit of resolution. This means since most listening is done in the -30dB range, if one were playing a CD with 16 bit resolution and attenuating at 30dB, only 11 bits of resolution would remain, an incredible loss. The Pandora volume control prevents all resolution loss by operating partially in the digital domain for small 1dB steps and partially in the analog domain using relay-based switched resistors for large 6dB steps. Using this method, eighty-eight 1dB steps are created with zero loss of resolution.

Select a Specification to Suit Your Needs

The Pandora is available in 3 versions, depending on the level of specification required.

Pandora MkII

• Tube DAC with AES/EBU, S/PDIF And USB inputs. Now with DSD & DSD 2X.
• Also available with the optional volume control – Contact our team for more information.

Pandora Signature Series

A Signature Series is a Pandora MkII with the following upgrades:

• True Native DSD
  Pandora Signature offer true native DSD 1x and 2x functionality over USB. The entire DSP processing section is replaced (pictured above, click to enlarge). The new section includes an advanced Xilinx gate-array which allows the DSP to be completely bypassed for pure DSD 1x and 2x operation. No alteration of DSD data occurs. Many DACs in the market that claim to play DSD actually convert the data to PCM and thereby completely lose the purpose of DSD operation.
• Vishay Z-Foil Resistors
  In addition to the DSP processing section, an entirely new analog board is installed that also allows DSD data to pass directly to the DAC, a Burr-Brown PCM1792A running in pure differential mode. Extremely low noise, high linearity Vishay Z-foil audio resistors are utilized in the critical current-to-voltage conversion stage.
• Dynamicaps
  The critical coupling capacitors are replaced with Dynamicaps from Peter Moncrief. Four are installed between the vacuum-tube gain stage and output stage, all in full differential mode. These provide increased resolution, less grain, greater high frequency extension and naturalness, all while maintaining the basic strengths of the Pandora’s tonal balance. The eight 2uF output capacitors are replaced with 4uF Dynamicaps which provide greater resolution in addition to improved bass definition, drive and dynamics.
• HRS Couplers
  The four standard rubber feet are replaced with Harmonic Resolutions Systems’ Nimbus Couplers specially made for Aesthetix. This lowers the noise floor and adds more air and space.
• Existing Pandora units are factory upgradable to Signature specification.
• Also available with the optional switched resistor volume control – Contact our team for more information.

Pandora Eclipse Series

An Eclipse Series is a Pandora MkII with the following upgrades:

• Internal changes start with .22uF / 600v Stealth coupling capacitors used between the gain stage and output stage. Four total of these exotic capacitors are used. There are four 2uF / 400v coupling capacitors used in each channel of the output stage. In the Eclipse version, these are replaced with Stealth copper foil 4uF/400v, improving low frequency response.
• The main transformer is re-installed on isolation mounts. Harmonic Resolutions Systems’ Nimbus Couplers specially made for Aesthetix replace the four rubber feet of standard units (as also found on the Signature version). The new power supply is installed with enhanced ventilation. Additional damping material is added to key chassis points.
• A single point ground system is used to ground the transformer cases as they are no longer electrically grounded to the chassis via physical contact due to their isolation mounts.
• Existing Pandora units are factory upgradable to Signature specification.
• Also available with the optional switched resistor volume control – Contact our team for more information.

Awards & Reviews

"This all-tubed CD player and DAC is one of the greatest bargains in high-end audio today. What makes the Romulus special is that it sounds so "un-digital," particularly at this price. Rather than sounding flat and congealed, the Romulus opens up the spatial presentation and gives instruments and voices room to breathe. The player has an expansive quality along with a sense of top-octave air and openness. The tonal balance is rich and warm in the bass, which, coupled with the treble smoothness, results in an immediately engaging and fatigue-free presentation. The Romulus doesn't sound "tubey" in the classic sense, but neither does it sound like solid-state. The design and build-quality are beyond what's expected at this price. If you have no analog sources, the Romulus can serve as a preamplifier and DAC with multiple digital inputs, provided you purchase the variable-output option ($1000). Thanks to an innovative hybrid analog/digital volume-control, there's no loss of resolution no matter what the volume setting."

-Robert Harley, The Absolute Sound Golden Ear Award (September 2014)

"The Romulus is another home run for Aesthetix, combining innovative circuit design, premium-quality parts and construction, and first-rate sound. This player was never anything less than musically communicative and immensely enjoyable, even in the context of a cost-no-object system. The Romulus is a flat-out bargain at its price, and invites comparison with much more expensive players. In fact, I’d call the Romulus a giant-killer, offering one of the highest price-to-performance ratios in digital playback today."

-Robert Harley, The Absolute Sound (May/June 2014), download PDF.

"Excellent dynamic impact and bass slam with sweet mids and highs."

-Jon Iverson, Stereophile Class A Recommended Component (2014)

"The Romulus delivers sound with a wonderful sense of space and ease. And detail? There’s loads. The player uncovers subtleties with considerable skill."

- What Hi-Fi? (UK, June 2014, ROMULUS DAC and CD transport), read review

"The build- and parts-quality are first-rate. Sonically, the Romulus offers an exceptionally natural sound with a great sense of ease and an expensive soundstage."

- Robert Harley, The Absolute Sound (March 2014), download PDF.

"(Romulus) has that combination of honey and of detail that enables you to listen to music for hours and never get tired or irritated."

- Hi-Fi i Muzyka Product of the Year Award (Poland, February 2014) read review

"...Romulus worked flawlessly and was a joy to use... the design, engineering, and build quality are top-notch for its price—and for the tube enthusiast, it's a no-brainer."

- Jon Iverson, Stereophile (2013, ROMULUS DAC and CD transport), read review.

"Klanglich einer der musikalischsten Player überhaupt... harmonisch, farbig, schnell und kraftvoll... vom Computer gelieferte Files habe ich persönlich in dieser Qualität noch nicht gehört."

-Michael Lang, STEREO (Germany, 2012, ROMULUS DAC and CD transport)

"Tonally one of the most musical players there is... harmonious, colorful, fast and powerful... I have never heard computer audio of this quality."

-Michael Lang, STEREO (Germany, 2012, ROMULUS DAC and CD transport)

"...vivid dynamic contrast... vibrant sound... excellent analytics... with a taste of vinyl texture..."

-Sam Ho, HiFi Review (Hong Kong, 2012, PANDORA DAC and ROMULUS DAC and CD transport)

HiFi Review
Product of the Year
(2011, Hong Kong, ROMULUS DAC and CD transport)