Toshiba XR-J9 CD Player Lab Report

Lab Report

As Tim suggests in his review, Toshiba's XR-J9 was an elegant but evolutionary dead-end in CD's family tree, employing a non-oversampled 14-bit TD6710N 'low power' integration-style DAC. The 22.7µsec interchannel delay and post-ringing caused by the sample-and-hold and analogue filtering, preceding the TA7415P line output amplifiers, are seen in the time domain impulse alongside the +0.5dB/10kHz peak in response prior to the –0.75dB/20kHz roll-off [Graph 2, below]. While its stopband rejection is a modest 25dB (24.1kHz re. 20kHz) the impact of the analogue filter bites more effectively >30kHz so that HF distortion harmonics are also suppressed. This is the reason why THD at 20kHz [blue trace, Graph 1] is 5-10dB lower than through the midrange [black trace] at signal levels below –18dBFs.

The player's 0.81V peak output is a little lower than the specified 1V while the ~850ohm source impedance increases to 990ohm at 20Hz, in tandem with a commensurate roll-off in bass response below 300Hz that reaches –0.2dB/20Hz [see Graph 1]. The 84.5dB A-wtd S/N ratio is bang-on the 14-bit specification, as is the drift in low-level linearity below –80dBFs which reaches +7.1dB/–90dBFs. Distortion falls to a minimum of 0.005%/1kHz at –10dBFs and 0.0055%/20kHz at –20dBFs while the peak level figures of 0.007%/1kHz and 0.018%/20kHz are still better than Toshiba's spec. back in 1986. The 75dB-rated channel separation is also remarkably close to the 76dB/1kHz measured here while, commonly quoted back in the day, the 'unmeasurable wow and flutter' roughly translates to what, some decades later, we broadly attribute to digital jitter. Establishing an accurate figure is complicated by the 14-bit DAC 'ignoring' the J-Test's low-level pattern, but ~1250psec looks very likely. PM


Distortion versus 16-bit CD digital signal level over a 120dB range (1kHz, black; 20kHz, cyan)


Time domain (note sample delay) and frequency responses on expanded scale (0.2dB/div)

Maximum output level / Impedance 810mVrms / 844-990ohm
A-wtd S/N ratio 84.5dB
Distortion (1kHz, 0dBFs/–30dBFs) 0.007% / 0.026%
Distortion & Noise (20kHz, 0dBFs/–30dBFs) 0.018% / 0.004%
Frequency response (20Hz-20kHz) –0.2 to +0.5dB
Digital jitter 1250psec
Resolution @ –90dB/–100dB +7.1dB / +7.3dB
Power consumption 5W
Dimensions (WHD) / Weight 252x50x130mm / 1.3kg