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The Hafler was auditioned with a variety of loudspeakers, but I spent most of my listening time with it in the company of the Vandersteen 2Ces. The preamp was the Rowland Consummate. Comparison amplifiers included the Aragon 4004 Mk.II, Sonic Frontiers SFS-80, and Krell KSA-250.

The CD transport was either the belt-drive C.E.C. imported by Parasound or the Pioneer Elite PD-65 used as a transport (the latter used primarily when the Wilson WATT/Puppies or the Apogee Stages were in the system), used to drive a PS Audio Ultralink via Kimber AGDL. The…

The Hafler 9500's input impedance measured just over 47k ohms. Gain into 8 ohms was 28dB. The output impedance was very low, ranging between 0.016 ohms and 0.022 ohms depending on frequency and load. This suggests a very consistent performance with a wide range of loudspeaker loads. DC offset measured 6.8mV in the left channel, 13.6mV in the right. S/N (unweighted at 1W into 8 ohms) measured 92.7dB. The 9500 was noninverting, a positive impulse at the input remaining positive at the output.

Fig.1 shows the frequency response of the 9500 at 2W into 4 ohms.…

Description: Solid-state, two-channel power amplifier. Power output: 250Wpc (8 ohms) (24dBW); 750W (8 ohms) (28.75dBW) in bridged dual-mono mode. Full power bandwidth: 0.15Hz–300kHz. THD: <0.03%, full power, 20Hz–20kHz into 8 ohms. Sensitivity: 1.8V RMS for full power. Input impedance: 47k ohms. S/N ratio: >100dB, unweighted.
Dimensions: 19" W by 12.5" D by 5.25" H (excluding feet, rack-mount version). Weight: 50 lbs.
Serial number of unit tested: D16C121000120.
Price: $1900 (black), $2000 (silver), rack handles $70 (option with black, standard…

War, poverty, global warming, starvation, racial inequality—these, among many others, were all trivial, long overcome matters of the past.

Generation ZZZZers glided around in auto-piloted, eco-friendly, space/time ships. They communicated with each other via holographic telekinetic mind messages. (Though there was always the occasional hippie, of course, who'd pull out a vintage, non-functioning wePhone 2000 or whatever technological dinosaur was making a comeback these days. Lame, if you ask me.)

Televisions were…

Some time ago, we mentioned the…

Esoteric…

To simplify this document we have grouped the topics and set them as questions and answers either as response, tutorial or axiom. Some months ago we published a comprehensive Q&A for an online forum and to avoid repetition we…

Answer: In essence, MQA is a hierarchical method and set of specifications for recording, archiving, archive recovery and efficient distribution of high quality audio. Devised by long-term collaborators Bob Stuart and Peter Craven, it has been developed by MQA Ltd. [1]

One axiom is that, in audio, High Resolution can be more accurately defined in the analogue domain in terms of temporal fine structure and lack of modulation noise than by a description in the digital domain, particularly if that description relies on sample rate or bit depth numbers. [2]…

Some questions have been posted in on-line comments and elsewhere:

• a) MQA made the unprecedented step of displaying the signal-to-noise (S/N) ratio of all of the charts and graphs not in "dBFS" (dB below Full Scale), but instead by presenting all of their data in "noise per-root Hz dBFS". An example of this was in the original AES Journal article [2]. In this paper, Figure 8 shows that 16 bits of data yields a –144dB noise floor and that 24 bits of data yields a –192dB noise floor. I personally am unaware of any scholarly article concerning digital audio…

The sounds we hear are rarely one thing, in fact sounds convey meaning by changing and combine tonal and atonal elements. Nevertheless engineers will spend a lot of effort using tones (single notes) to investigate frequency response and non-linearity. Similarly we measure noise to try to understand how much there is. In our world background noise is an irremovable feature. A recording system adds noise as do distribution and replay systems. If we are to design or specify or compare, we need a framework within which to be able to estimate…