Classé Audio Delta PRE/MONO DAC/Preamp & Monoblocks Lab Report

Lab Report

Sailing past its rated 300W/8ohm, Classé's Delta MONO punished the lab test loads with a full 410W/8ohm and 760W/4ohm, the very stiffly-regulated PSU going on to support 420W, 790W and 1361W into 8, 4 and 2ohm loads under dynamic conditions at very low levels of distortion [see Graph 1, below]. Power into 1ohm cuts at 1203W (34.7A) and the Delta MONO enters standby. Distortion is indeed exceptionally low through the Delta MONO's Class A range, from 0.0003%/100mW to 0.0002%/1W, 0.0001%/10W, 0.0003%/100W and 0.0006% at the rated 300W (all 1kHz/8ohm). Residual noise is low too, and the A-wtd S/N a wide 92.6dB (re. 0dBW) for an overall gain (balanced in) of +29.1dB. The response is flat to –0.05dB/20kHz and –0.6dB/100kHz and output impedance low at 0.01ohm.

The Delta PRE analogue preamp offers a huge 20V maximum output (balanced), a gain of +14.3dB, distortion gently increasing from 0.0002-0.0016% (0dBV, 20Hz-20kHz) and a promising 98dB A-wtd S/N ratio. The response rolls out to –0.2dB/20kHz to –6.4dB/100kHz although the AK4497-based DAC section, with steep roll-off linear phase filter selected by Classé, has its 'own' response of –0.2dB/20kHz, –0.8dB/45kHz and –3.1dB/90kHz with 48kHz, 96kHz and 192kHz media, respectively. Set to a 4V (balanced) output for a 0dBFs digital input, the PRE offers a very wide 115dB A-wtd S/N ratio and distortion is a consistent ~0.0014% (20Hz-20kHz). THD falls to a minimum of 0.0002-0.0007% over the top 30dB of its dynamic range [see Graph 2] and low-level linearity holds good to within ±0.1dB over a full 110dB dynamic range. Jitter meanwhile is suppressed to ~50psec across all inputs/sample rates. PM


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 34.7A


Distortion versus 24-bit digital signal level over a 120dB range (1kHz, black; 20kHz, blue)

Continuous power (<1% THD, 8/4ohm) 410W / 760W
Dynamic power (<1% THD, 8/4/2/1ohm) 420W / 790W / 1361W / 1203W
Output imp. (20Hz–20kHz, Pre/Amp) 96ohm / 0.010-0.025ohm
Freq. resp. (20Hz–20kHz/100kHz) +0.0 to –0.19dB/–6.4dB (Pre)
Digital jitter (USB / S/PDIF) 50psec / 45psec (48kHz/24-bit)
A-wtd S/N ratio (DAC/Amp) 115.2dB (0dBFs) / 92.5dB (0dBW)
Distortion (DAC, 0dBFs/Amp, 0dBW) 0.0002-0.0003%/0.0004-0.0008%
Power consumption (Preamp/Amp) 36W / 540W (255W idle)
Dimensions (WHD, each unit) 445x121x445/444x222x492mm
Prices (DAC/Pre & Monoblocks): £9999/£10,999 (each)

Sound United, Shirakawa Audio Works
Supplied by: Sound United UK, Kingston-upon-Thames
0208 103 4770