Proceed CD player Measurements

Sidebar 2: Measurements

The Proceed showed no surprises on the bench. Frequency response was extremely flat, with a very slight rolloff (–0.1dB right, –0.2dB left) at 20kHz, though there was a minor deemphasis error of +0.2dB at 16kHz. Spectral analysis of a –90dB, dithered 1kHz signal, shown in fig.1, revealed a low level of HF spuriae, though some linearity error can be seen by the –90dB recorded signal rising above the –90dB horizontal division. Somewhat surprisingly, this implied positive level error was not apparent on a plot of departure from linearity (fig.2). Checking with a 1/3-octave spectrum analyzer suggested that it is fig.2 that is correct. not fig.1, with a –2dB error apparent between –70 and –90dB.


Fig.1 Proceed CD player, dithered 1kHz tone at –90dBFS with spuriae and distortion (right channel dashed).


Fig.2 Proceed CD player, left-channel linearity error (2dB/vertical div.)

The "fade to noise with dither" track on the CBS test disc resulted in a fairly straight line (fig.3), indicating good differential linearity. It also sounded exceptionally pure as it decayed, with no harmonics audible, just rather hashy-sounding noise.


Fig.3 Proceed CD player, left-channel fade to noise with dither.

In addition, linearity was nearly perfectly matched between channels. Looking at the low-level waveforms with a storage 'scope indicated that audio-band noise was a little higher than with some other machines, though the absolute noise floor was still below –90dB. Fig.4 shows the –80.77dB undithered 1kHz tone from the CBS test CD: what should be a stepped waveform with seven distinct levels is obscured by the noise present. Similarly with the undithered –90.31dB tone shown in fig.5. This waveform consists of just three levels, +1, –1, and digital zero, but this can be seen to be overlaid with around half of an LSB's worth of noise. The same is true of the monotonicity trace (fig.6), which should feature 10 distinct "steps" in the waveform, but is somewhat obscured by noise. The straight slopes, however, suggest good differential linearity.


Fig.4 Proceed CD player, undithered 1kHz tone at –80.77dBFS (5ms time window).


Fig.5 Proceed CD player, undithered 1kHz tone at –90.31dBFS (5ms time window).


Fig.6 Proceed CD player, monotonicity waveform (100ms time window).

The high-level performance of the Proceed's digital filter is revealed by fig.7, which shows how the player reproduces a 0dB, 1kHz squarewave. The flat tops to the waveform suggest that the digital filter actually clips with this signal, while a slight asymmetry is also apparent, the negative "tops" appearing to have a slight HF roll-off compared with the positive "tops." This is a severe test signal, however, and one that is hardly likely to be met in real-life music. Nevertheless, the Proceed might be expected to sound a little hard with extremely hot CDs, such as the Bainbridge Stephen Kates Rachmaninoff recording.


Fig.7 Proceed CD player, 1kHz squarewave at 0dBS (2ms time window).

The Proceed's error-correction capability was tested with the second disc of the Pierre Verany set (PV.788032). It proved to have some problems with the larger dropouts, anything over a 1.5mm gap in the data leading to repeated blips in the sound. Finally, its maximum output is 0.5dB higher than the standard 2V, which will be audible on an A/B comparison. Take care when auditioning to match levels carefully.—Robert Harley

dickeyn's picture

I still have this unit and it continues to work well ( has only needed a cleaning since purchased in 1990). It was chosen at the time because it sounded closest to LP's. The Proceed even manages to play "home-made" CD+R's (except Sony) even though not designed for them at the time.

It is now relegated to the bedroom system due to being replaced by a Bryston unit for the main sytem (greater extension in the upper and lower frequencies - more detail).

Neil D.