B&O Beogram CD X Lab Report

Lab Report

As Tim describes in our review, this exquisite CD player from yesteryear employs the same diecast CDM1 swingarm transport, servo, decoder and oversampling/DAC boards as the Philips CD104 [HFN Apr '14]. Both these players were based on the seminal SAA7030/TDA1540 14-bit/4x oversampling chipset, the DAC itself proving to be very linear down to –70dBFs (within ±0.1dB) but showed a slightly compressive trend thereafter with signals at –80dBFs emerging at –77.2dB and those at –90dBFs at –86.6dB, etc. B&O's improved PSU shielding ensured the Beogram CD X offered a superior 107.3dB A-wtd S/N ratio but the practical resolution of the player is still closer to 15- rather than 16-bits. There are two TDA1540 DACs in this player, one for each channel, and its interchannel phase matching and stereo separation improve accordingly, the latter >90dB (20Hz-20kHz).


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


High res. CD jitter spectrum (mkrs show 45 discrete jitter patterns amounting to a low 350psec)

Meanwhile, the limited number of taps in its first-generation SAA7030 linear phase FIR digital filter offer a reasonable 51dB suppression of aliasing images and a frequency response just –0.45dB down at 20kHz (–0.75dB/20kHz with pre-emphasised CDs) but also produces in-band ripples amounting to 0.25dB [see Graph on Page 2 of this review]. Distortion is low for a 14-bit architecture at 0.002-0.003% at its peak 2.09V output (20Hz-20kHz) but the trend of THD versus digital level is much more erratic than the smooth 'textbook' diagonal achieved by modern DACs [see Graph 1]. Digital jitter – not measurable back in the day – is a very respectable 350psec [see Graph 2] although the spectrum is highly complex and populated with low-level PSU, data-induced and other sidebands related to digital processes within the CD X. PM

Maximum output level / Impedance: 2.09Vrms at 47-515ohm
A-wtd S/N ratio: 107.3dB
Distortion (1kHz, 0dBFs/–30dBFs): 0.0022% / 0.025%
Distortion & Noise (20kHz, 0dBFs/–30dBFs): 0.0030% / 0.0070%
Frequency response (20Hz-20kHz): +0.05dB to –0.45dB
Digital jitter: 350psec
Resolution @ –90dB/–100dB: +3.4dB / +3.5dB
Power consumption: 16W
Dimensions (WHD) / Weight: 420x75x310mm / 5.6kg