Exposure CD Player

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Exposure owner/designer John Farlowe graduated from the UK’s University of Sussex at the end of the swinging ’60s. He put his B.Sc in electronic engineering to use at HiWatt, manufacturers of tube guitar amplifiers. His keen interest in pro audio, particularly in sound reinforcement for rock bands, led him to Midas (studio mixing desks and systems), where, as director and designer, he designed and built mixing desks and got together with the late Dave Martin of Martin Audio. They became heavily involved in sound systems for Pink Floyd. Midas desks and Martin speakers were used at many live venues, including those at London’s Rainbow.

Seeking a quieter life, Farlowe founded Exposure Electronics—a small, specialist British audio company based in Brighton, Sussex, UK—some 20 years ago, and has since concentrated on high-end home audio. He has quietly built up an enviable if low-key reputation for his essentially handcrafted solid-state electronics, built using carefully selected transistors and classic discrete circuits. He uses traditional technologies, capacitor coupling at low level, and DC coupling at the power-amplifier outputs.

In our discussion about the design of his CD player, John Farlowe related his long experience with the effects of power-supply components on sound quality. His standard practice is to optimize amplifier performance by using oversized toroidal transformers wound to an exacting specification. Reservoir electrolytic capacitors are also built to his own specification. He is also a fan of open-loop, non-feedback regulation for power amplifiers; even his small Type 25 integrated amplifier has fully stabilized supplies for its output stages.

Farlowe has remained an analog enthusiast. He continues to design LP phono stages while patiently observing the industry scramble to integrated circuits, microprocessors, and digital processing and digital audio. But until now, the Exposure range of amplifiers hasn’t included source components. Conservative (with a small c) almost to a fault, Exposure long resisted the march toward user convenience and digital sources.

Then, a year ago, an upgraded version of Exposure’s popular integrated amplifier included what was for them a remarkable advance: remote-control of input selection and volume. Still more extraordinary was the presence on the remote handset of an array of ancillary buttons whose purpose was nothing less than the control of a CD player—Exposure did not manufacture a CD player. We were assured that the remote would “operate any player you choose with Philips-compatible software.”

But the writing was on the wall. A year later Exposure announced that they had reached the point of product approval for a CD-player design long cooked up in their research labs. And here it is—their first digital replay product, their first source component, and the subject of this review.

Perhaps the last of the classic audio companies to embrace digital technologies, Exposure is still treading cautiously. Many CD technologies were examined, including designs from both Japan and Europe. The decision to release a digital audio product was delayed until Farlowe felt the sound quality attained compared favorably with established standards for analog replay, and would thus complement Exposure’s current amplifier range. This first CD player has the inevitable integrated circuits for data recovery and digital/analog conversion, but after this point, and in line with the company’s design philosophy, the circuitry is wholly discrete, executed in classic Exposure fashion.

Technology
The $1995 Exposure CD player is a one-box, full-size CD player with a fixed analog output of nominal 2V level and front-drawer–loading. The case is traditional Exposure: sheet metal (argon-welded aluminum) with a thick anodized alloy front panel and a modicum of acoustic damping on the aluminum top cover. Following the current fashion for upmarket products, front-panel controls are reduced to a minimum: Play, Stop, Next, Previous Track, and Repeat. A fully equipped numeric keypad is provided on the remote handset, which offers quick track access and sequence programming. The handset has a good operating range of up to 30′ under normal lighting conditions.

The choice of a single-box design was deliberate in order to be competitive with designs from Audiolab, Marantz, Meridian, and the like. With the data-retrieval system directly coupled to the digital filter and thence to the DAC, the system suffers minimal jitter: there is no interface in the way. In a two-box player, the S/PDIF or AES/EBU interfaces can introduce significant jitter whose rejection is then the responsibility of sophisticated and costly input circuitry in the DAC. Even with extensive precautions, jitter removal is never entirely certain or complete. Time and again, the most elaborate jitter-busting techniques—even those involving large static memory—do not achieve absolute timing precision.

In common with some US majors such as Conrad-Johnson and ARC, Exposure has chosen a relatively simple Philips platform on which to found this design. For the transport, the ubiquitous CDM-12.4 is used, noteworthy for its effective if simple anti-vibration suspension of molded polymer, and its noiseless, low-mass magnetic disc clamp. High-quality power is derived from a large toroidal transformer with segregated secondary windings and generous reservoir capacitors of power-amplifier grade.

The Philips “engine” or microprocessor and transport control section includes the digital filter. In addition to some proprietary modifications, the crystal oscillator in the Philips engine is disabled and a separate low-jitter, buffered oscillator is installed, provided with its own local supplies and a high-precision crystal.

The digital filter is unremarkable; it’s a low-order type beneficially related to the much-respected Philips 7220 series. In common with the older filter, there’s some mild passband ripple evident, if of questionable audibility. De-emphasis is accomplished in the digital domain. There is also a digital volume control embedded in the digital filter chip (more on this later).

The 8x-oversampling filter outputs 16-bit words to the TDA 1545 surface-mount DAC, a multibit two-channel part using Philips “CC” (Continuous Calibration) technology to maintain 16-bit linearity. This also has some parallels with a long-established Philips multibit DAC, the TDA 1541A, with which it shares a “kink” in the linearity curve below –80dB. This leads to 3–4dB of level error at –90dB. As with the 1985 ‘1541A, some sense of order returns below –95dB.