Integrated Amplifiers

Our original CD11/A11 review carried an in-depth Lab Report [HFN Oct '19] so while the intervening period has necessarily seen some running production efficiencies at the Rotel factory it is still possible to measure and identify the 'fingerprint' of these new MUSE coupling capacitors. The slight reduction in output level from 2.1V to 2.07V, the 450ohm to 448ohm output impedance and improvement in A-wtd S/N from 108.1dB to 108.2dB (CD11 to CD11 Tribute) all fall within the compass of production variation while other parameters, including the 116psec jitter, 63.6dB stopband rejection and ±0.04dB response ripple, are 'fixtures' of the Burr-Brown/TI PCM5102A DAC. THD over the top 20dB of the CD11's dynamic range has increased slightly, however, from 0.004% to 0.008% (0dBFs) and 0.0012% to 0.003% (–10dBFs) through the midrange [dotted red trace vs. black infill, Graph 2]. While this increase in (mainly 3rd) harmonic may not be directly audible in itself, it is indicative of change.

The partnering A11 Tribute amp now has +0.5dB extra gain, the same 80.3dB A-wtd S/N ratio (re. 0dBW) and delivers a hint less power at 2x75W/8ohm and 2x105W/4ohm (vs. 78W/110W) albeit with a near-identical dynamic output of 113W, 194W, 187W and 78W (protected) into 8, 4, 2 and 1ohm loads [Graph 1]. Also, rather than being held to a tight 0.004-0.006% distortion (re. 1kHz) over its rated 50W range, THD increases in the A11 Tribute above 10W, reaching 0.014%/20W and 0.03%/50W – but only under continuous rather than dynamic conditions... Also, the HF resp. is now flatter, from –0.3dB/10kHz and –0.6dB/20kHz (A11) to –0.04dB/10kHz and –0.10dB/20kHz here. PM