Krell KAV-300cd CD player Measurements

Sidebar 3: Measurements

I measured the Krell's performance from both its balanced and unbalanced outputs. Except where noted, my comments refer to the balanced outputs. With a full-level 1kHz sinewave, its output was 4V from the balanced outputs, 2V from the unbalanced. Channel balance was superb at within 0.01dB. The output impedance was a low 16 ohms from the unbalanced outputs, 32 ohms from the balanced. Absolute polarity was correct from both sets of outputs, the balanced wired with pin 2 hot.

The KAV-300cd's frequency response is shown in fig.1: absolutely flat from 10Hz to 10kHz, with just a slight (0.1dB) droop in the top octave. De-emphasis error (not shown) was nonexistent, while crosstalk was low, at better than -80dB across the band.

Fig.1 Krell KAV-300cd, balanced mode, frequency response (right channel dashed, 0.5dB/vertical div.).

Fig.2 shows the 1/3-octave-smoothed spectrum of the Krell's output while it decoded data representing a dithered 1kHz tone at -90dBFS. Other than a very slight hint of some second harmonic and some low-level power supply noise at 120Hz—this remained evident despite my trying different grounding arrangements—the trace is free from spuriae. Repeating the spectral analysis with a "digital black" signal and extending the measurement bandwidth gave the trace shown in fig.3. Other than the residual 120Hz component, the plot is free from idle tones an other spuriae.

Fig.2 Krell KAV-300cd, balanced mode, spectrum of dithered 1kHz tone at -90.31dBFS, with noise and spuriae (16-bit data, 1/3-octave analysis, right channel dashed).

Fig.3 Krell KAV-300cd, balanced mode, spectrum of digital silence (16-bit data, 1/3-octave analysis, right channel dashed).

The PCM1702 DAC is known for its good linearity, as can be seen in fig.4, which shows the left channel's departure from linearity using the dithered 500Hz tone on the CBS Test Disc. Any error remains below ±0.5dB until -100dBFS, below which the dither noise increasingly dominates. As a result of this good performance and the player's low noise level, the waveform of an undithered 1kHz tone at -90.31dBFS (fig.5) can be seen to consist of two equal-sized steps either side of the time axis, with the Gibbs Phenomenon "ringing" clearly visible at each bit transition. This is excellent performance, implying superb resolution.

Fig.4 Krell KAV-300cd, left channel, balanced mode, departure from linearity (2dB/vertical div.).

Fig.5 Krell KAV-300cd, balanced mode, waveform of undithered 1kHz sinewave at -90.31dBFS (16-bit data).

Hitting the player with an equal, full-level mix of 19kHz and 20kHz tones gave the spectrum shown in fig.6. Intermodulation products are all very low in level. The KAV-300cd was only a moderately good tracker, it not being able to cope with gaps in the data more than 1mm in length (track 32 on the Pierre Verany test CD), though it is fair to point out that the CD standard only asks for a player to be able to correct for a 0.2mm dropout. Finally, it was not possible to measure the Krell's jitter. However, Stereophile has recently acquired a Paul Miller analyser, which will allow us to measure the effects of word-clock jitter in the analog domain. We will look at the KAV-300cd's jitter performance in a Follow-Up.

Fig.6 Krell KAV-300cd, balanced mode, HF intermodulation spectrum, DC-22kHz, 19+20kHz at 0dBFS (linear frequency scale, 20dB/vertical div.).

All in all, this is an impressive set of measurements.—John Atkinson

45 Connair Rd.
Orange, CT 06477-3650
(203) 799-9954