Integrated Amp Reviews

Stereophile often subjects products that have been reviewed to further coverage: sometimes because there was an aspect of performance that needed further investigation; other times because there was a controversial finding. Three recent followups concerned the Ayre Acoustics EX-8 2.0 Integrated Hub amplifier that Ken Micallef reviewed in the November 2021 issue; the Accuphase DG-68 Digital Voicing Equalizer that Jason Victor Serinus reviewed in August 2021; and the Zesto Leto Ultra II line preamplifier that Ken Micallef reviewed in February 2021.

When I measured the sample of the Ayre EX-8 2.0 that had been auditioned by KM, the right channel had a significantly higher output impedance than the left and that channel's distortion signature was different. Ayre's CTO Ariel Brown conjectured that a shock in the sample's shipping to me had led to a solder joint in one the right channel's output devices failing. Ayre shipped a different sample to me and both channels now performed identically on the test bench, as you can see from my followup.

Zesto's Leto Ultra II preamplifier has an unusual "Presence" control that progressively rolls off the high frequencies in five steps. This is intended to tame the high end on especially rowdy recordings and Jim Austin investigated the control's effect with several familiar recordings that indeed had "rowdy" high frequencies. He found that specific settings worked well with some recordings and concluded that "This is a great preamp, pleasantly and unusually styled, with a useful and unusual feature."

When he reviewed the Accuphase DG-68 Digital Voicing Equalizer, Jason Victor Serinus exclusively used its analog inputs and outputs to investigate the improvement it made to his system's in-room balance. However, the DG-68 also has digital inputs and outputs and I wondered whether using the equalizer with pure digital-domain correction would produce even better results, due to the absence of two conversions, one from analog to digital and the other back to analog.

With the DG-68's levels carefully matched to those of his reference gear, JVS found with one of my recordings that "The DG-68's digital in/out connection not only delivered the all-important three-dimensionality that John strove for; it also compensated for my room's bass rolloff by bringing out all-important bass lines and fleshing out voices in ways not previously audible through my system.

He concluded that "The more time I spent with the DG-68, the more I appreciated how much it can do, and how easy it is to play: to try things and listen and revise less than optimal choices or eliminate them entirely."