Associated Equipment:
Digital Front End
Amplification
Loudspeakers
Cabling
Accessories
Audiocom Superclock II and Superclock Power Supply mod for digital, Modification by Audiomod on Audio Note CDT-2 Transport

Mods for the Digital Front End Transport

Michael Girardi

October 24,2003

Specifications

Audio Note CDT-2 Transport
1 x balanced AES/EBU digital output
1 x single ended digital output

Extruded ribbed aluminun chassis
Audiocom Superclock 2
Dimensions: 8.5” x 14” x 4” (WxDxH)
Chassis color: silver or black
Weight approx.: 18 lbs

Audiocom Super Clock II
Printed circuit board employing low impedance ground plane, Black Gate and Os-Con electrolytic capacitors, and low phase noise oscillator circuit.

Audiocom Super Clock Power
Printed circuit board employing low noise transformer, IR schottky diodes, Black Gate capacitors throughout and fully discrete 12-volt DC regulation.

Prices:
Audio Note CDT-2 Transport, $2950.
Audiocom Superclock II, $277.
Audiocom Superclock Power Supply, $265.

Addresses:
Audio Note (UK) Ltd.
Unit C Peacock Industrial Estate,
Lyon Close,
Hove,
East Sussex
BN3 1SG
United Kingdom
Tel: +44 (0)1273 220 511
Fax:+44 (0)1273 731 498
http://www.audionote.co.uk

Audicom International Ltd
Unit 14 Pier Rd
PEMBROKE DOCK
Pembrokeshire
SA72 6TR
United Kingdom
Tel: +44 (0)1646 685601
Fax: +44 (0)1646 685602
http://www.audiocom-uk.com

Reference Audio Mods (RAM)
Kyle Takenaga (USA Distributor for Audicom)
16230 Stone Hill Court
Riverside, CA 92503, USA
Tel: 909-353-8948
Primary: sales@referenceaudiomods.com

Audiomod
Richard Kern
4390 SE Mark Kelly Court.
Oak Grove, Oregon 97267
503 659-6599 or 503 490-8602
http://www.audiomod.com


Components that make-up the System

Audio Note CDT-2 Transport

The Audio Note CDT-2 CD drive is the product of research undertaken by the designer Andy Grove and Peter Qvortrup. See the Audio Note website article, “Are You on the road to Audio Hell?” to get an appreciation for their design philosophy.

The transport incorporates nearly full implementation of Black Gate capacitors (except one whose value is not offered by Black Gate), two copper wound digital pulse transformers, Philips CD12 drive unit, and a Sony digital front end. The ¼” thick aluminum front panel contains a vacuum fluorescent display. The rear panel houses the on/off button, IEC female receptacle for aftermarket power cords, one balanced and one single ended digital gold plated connector. For it’s size, the AN CDT-2 is one heavy sucker.

The user interface of the AN CDT-2 is the most unique component I have ever owned. Front panel controls do not exist. All user functions are operated through the supplied infrared remote. CDs are loaded from the top by removing a manual lid, a magnetic puck is removed to allow CD loading on a spindle, and the magnetic puck is then replaced to secure the CD. The manual lid is then replaced to allow direct control through the remote.

One should plan for a break-in of over 3 months due to the implementation of Black Gate capacitors, before the sound of the CDT-2 can be fully enjoyed. It is also recommended that the AN CDT-2 be allowed to warm-up for 30 minutes before serious listening. Based on additional experimentation, I have found that the AN CDT-2 benefits from the use of the Marigo Orpheus Crossbow CD Mat, a set of Still Points with Risers, and the Foundation Research LC1 power conditioner/ cord.


Audiocom Superclock II

The Audiocom Superclock II is designed and manufactured by Audiocom International, which is located in the United Kingdom. Audiocom offers a range of audio products from upgrade parts to the service to install upgraded parts in CD, SACD, and DVD players.

Quoting directly from the Reference Audio Mods (RAM) website, “The basic platform of the Superclock II is its printed circuit board. This is formed as an extremely low impedance ground plane over which the components are placed. Very low impedance ground planes contribute to signal quality and are essential when handling radio frequency signals, which are of exceptionally low distortion and phase jitter. The ground plane shields the radio circuits from the invisible capacitor formed when the board is mounted close to metalwork.” Components comprising the Superclock II include the best available Black Gate and Os-Con type electrolytic capacitors.

According to what is reported on the Audiocom website, the design of the Superclock II was achieved through extensive product research and listening tests. The radio frequency circuits which generate the clock, were over specified for their intended application (CD or DVD). To meet this high frequency design requirement, the resulting strip line layout of the PCB and electronic components provide for the shortest signal path. The low phase noise oscillator, which is proprietary to Audiocom, “ … uses two Ultra High transistors in a unique arrangement to produce a very clean signal at the clock’s fundamental frequency, having minimal wave form and phase distortion.”

The Superclock II is a second-generation device possessing the following design/performance enhancements as compared to its predecessor:

• Improved oscillator circuit for better short-term and long term stability
• Wider bandwidth low noise RF buffer & amplifier stage
• Newly developed sine-square wave circuitry
• Lower data related and power supply jitter
• 40% shorter signal path.

It’s been well documented that the effect of jitter has been one of the main weaknesses of digital playback since it’s inception over 20 years ago. Jitter in CD playback directly affects system time coherence. The ear–brain perceives this smearing as blurring, veiling of the sonic portrait, flattening of the soundstage, unnatural tension in the emotion of the music, harshness, and frequency response unevenness. The Audiocom Superclock II was developed to minimize these deleterious effects.

Audiocom Power Supply for the Superclock II

As stated on the RAM website, “At the heart of the Superclock power supply are two pieces of the identical non-polarized Black Gates, the inherent resonance generated by the capacitors internal inductance is totally cancelled, and the impedance and E.S.R. values infinitely decrease as frequency rises. This system of connection is referred to as "Super E-Caps". The regulation is based around a 2-stage ultra-low noise, high-speed series regulator employing high-grade operational amplifiers from analog device. The filter section of the regulator again uses the "Super-E cap" system to achieve ultra-low noise operation.” The component layout of the Superclock power supply board consists of a low noise transformer, IR schottky diodes, Black Gate capacitors throughout, and fully discrete 12-volt DC regulation.

The design goal of the Superclock power supply is to reduce phase noise and jitter in the high frequency operation of the Superclock II. Filtering of the low/high frequency noise from the incoming ac supply and the reflected noise generated internally by the digital circuits are additional functions performed by the Superclock power supply. In addition, the op amp in the Superclock PS is configured to provide more current than is actually required by Superclock II, resulting in a very stable power source. The Audiocom Superclock PS was design to be used in conjunction with the Superclock II.


The Sum of the Parts is Greater than the Whole

My quest to assemble a system based on a digital source began with the California Audio Labs CL-15 CD player and a Golden Tube Audio amplifier and preamplifier. My system later consisted of the Sony SCD-777ES SACD player, and amplifier and preamplifier from Aloia. When I replaced the CL-15 with the SCD-777ES and the other associated components, I was convinced that digital finally had the potential to be a high-end playback format. Following an extensive break-in on the Sony SCD-777ES, I found the redbook playback on the SCD-777ES thin sounding, fatiguing and lacking life. Since my music collection of the time consisted of 98% redbook CDs, I took on the adventure of assembling a system that would emulate SACD without being limited to the software available on SACD.

Initially, I replaced both my Aloia amplifier and preamplifier with amplification components from TacT Audio: the Millennium MKII amplifier and RCS2.0 DD preamplifier.

As stated on the TacT Audio website, the Millennium MKII amplifier “employs a PWM amplification stage to amplify a digital signal and couple it directly to the loudspeaker without converting it into the analog domain” replacing conventional D/A conversion and analog amplification. The amplifier circuit is based on proprietary PCM-to-PWM EQUIBIT technology. “EQUIBIT simplifies the signal path from the digital signal source to the speakers. A unique digital processor circuit controls the power output devices directly using digital pulses”. Analog feedback or analog signal processing/amplification is not used at any stage of the circuit. In summary, the TacT Millennium is a “high-power DAC device that translates digital information directly into sound”. The Millennium MkII does not employ analog circuitry after D/A conversion other than one coil and one capacitor performing a 60 kHz, 2nd order low-pass filter. The Tact Audio RCS2.0 DD is a preamplifier that incorporates a room measurement and correction system addressing the speaker/room interaction.

The next step on my road to audio Nirvana included the auditioning of the Audio Note CDT-2 transport. During my review I choose to use the balanced digital output of the AN CDT-2 connected to the balanced input on the RCS2.0 DD. I also used the balanced digital output of the RCS2.0 DD and connected it to the balanced input on the Millennium MKII. Stealth Varidig cryogenically treated AES/EBU digital interconnects were used in both cases. My review system also included the Talon Audio Khorus X MKII speakers, Stealth Hybrid MLT speaker cables, Still Points and Risers, and Foundation Research LC1 powerline conditioner/cords on front end components and FR LC2 on the Tact Audio Millennium. The Sony SCD-777ES was connected to the TacT RCS2.0 DD via the single ended output and Stealth Varidig digital cable.

The untweaked AN CDT-2 transport ran circles around the Sony SCD-777ES using red book CDs as the source. The CDT-2 had an intoxicating musicality. The first differences I noticed were the complete blackness between notes, the great sense of air and space around instruments, improved decay, less haze/grit/grunge, and low level spatial cues that were previously unrevealed on the SCD-777ES. Dynamic contrasts were also more easily discerned, thereby better communicating the emotion in the music as compared to the SCD-777ES. The tonal balance on the SCD-777 was also darker when compared to the AN CDT-2. It appeared, from my listening tests, that the extensive use of Black Gate capacitors in the transport circuit had a profound effect on the overall performance. Judging components based on believability, the AN CDT-2 received a much higher mark. Bear in mind, on paper this may not be a fair comparison since the AN was designed to serve one purpose (function as CD transport) whereas the Sony SCD-777ES was designed to perform many functions (DAC, transport).

It’s always been my belief that one cannot invest enough in the front end of one’s system. After reading all of the press concerning better parts substitution on Audio Asylum, I wondered if this transport could be tweaked further. Since the CDT-2 does not employ jitter reduction circuitry it was thought that replacing the existing clock and clock power supply would provide the greatest benefit in terms of jitter reduction. I arranged to have my AN CDT-2 sent to Richard Kern to replace the original 33.8688 MHz clock with the Audicom Superclock II and Superclock Power Supply. The cost for the mods, including parts, installation, and testing was $742, plus shipping both ways. Richard Kern provided excellent turnaround and customer service during the entire process. After receiving the tweaked transport, I let the new components break-in for what seemed to be an eternity.

So what’s was the verdict following this extensive break-in? All areas of the digital playback were affected in the most beneficial way:

• Immediately apparent was the expanded soundstage. Instruments were better located in space, with the soundstage width extended well beyond the speakers. The depth of the soundstage took on a more complete venue, filling all the corners. There was also a contrasting ambience and sonic signature from each CD depending on whether I was spinning a jazz or contemporary rock CD.
• The imaging improvements helped to better flesh out the instruments in space. There was increased texture and substance to vocals and instruments, yet possessing a smoothness through the entire frequency spectrum. The outlines of the string instruments were also better portrayed.
• A significant improvement in dynamics and transient response was conveyed by the untweaked AN CDT-2. With the Superclock installed, the micro/macro dynamics were better delineated communicating the emotion of the music.
• Faster, more accurate bass with lifelike definition, timing, and decay.
• The resulting lower noise floor further enhanced detail, coherency and transparency. The combination of the two (mod and transport) rendered the most complex musical passages, which can sound distorted on digital playback in most systems I’ve heard, become alive and real.

Conclusion

Was the original goal of constructing a system that emulates SACD met? The goal was met and exceeded. The new system brings you closer to the original performance: You are there and they are in the room.

Jitter reduction has a profound effect on reproduced music. The Audiocom Superclock II and Power Supply are the cure for jitter.

The Audio Note CDT-2 is not the best transport money can buy but its an excellent transport for its asking price. In my system, the advantages of a dedicated transport specifically designed for the function of reading the data on a CD, were clearly demonstrated.

Of the available modifications (capacitors, resistors, diodes, etc), the Superclock II and Power Supply is the best place to start on the modification path. Highly recommended if you’ve already selected cables, your system is mechanically isolated, and there is a good synergy between the components in your system.
 

 

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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