Sumo Athena preamplifier
The Athena is, at present, Sumo's only preamplifier (their previous model, the Electra Plus, has been discontinued). It is aimed at the audiophile looking for the basics without the frills: standard balance, volume, tape (two, with dubbing in either direction), high-level, and phono stages. Gain is adjustable, via an internal switch, to accommodate nearly all cartridges, from low-output moving-coils to their higher-output cousins, as well as moving-magnets. A low-frequency filter is provided to cut the response of the phono input below 70Hz with a first-order slopea rather high cutoff but a gentle filter action.
A bypass switch eliminates the high-level stage from the signal path when desired. Whether or not you can use this will depend on the gain in the rest of your system; your circumstances may differ considerably from mine. For that reason I did most of my auditioning with the high-level stage in-circuit, a condition under which there's plenty of gain for any home system I can envision.$s1 The primary sonic result of bypassing the high-level stage of the Athena was a slightly sweeter extreme high end and a moderate but noticeable reduction in dynamics.
Amplification stages of the Athena are all discrete and all class-A, as, in fact, are most discrete solid-state preamps these days. A high-current toroidal power transformer is used, its flat profile allowing the preamp to assume its slim design. Sumo makes a point of the Athena's dynamic headroom and freedom from overload. Overall build quality is very high, but not in the class of super-priced preamplifiers. Although I'm not a big fan of front-panel input indicator lights, their use here does make the position of the selector switches clear (despite some minor bleed-through of the light to adjacent positions). Both the volume and concentric balance controls are stepped potentiometers. They can be set between steps with a little care, which is fortunate since the gradations in the 10 to 1 o'clock settings (the most used positions in my system) are 2.5 to 3dBa bit coarse. I prefer continuous controls.
I generally leave preamplifiers on all the time, and did so with the Athena as well. But for those who don't, the Sumo preamp has no turn-on or turn-off pulse; the output is muted for 15 seconds at turn-on to allow for stabilization of the circuitrya welcome feature.
Listening to the Athena with CD driving its high-level stage was ear-opening. My notes are full of vivid adjectives. Detailing was excellent, but without obvious exaggeration. Nojima Plays Liszt (Reference Recordings RR-25CD, reviewed in Vol.11 No.4) was exciting and alive; even Nojima's flying fingernails tapping the keyboard on certain selections were clearly evident but not distracting. The drum set on the Hi-Fi News & Record Review Test Disc (HFN 003) was punchy and dynamic, and the big drum on Kodo (Sheffield Lab CD-KODO) was little short of awesome. Nor was simpler material slighted. The superb sampler from Dorian Recordings was reproduced with an open, airy, transparent quality.
I did note a very slight tendency to brightness through the high-level stage, and some foreshortening of depth and three-dimensionality, but, overall, it was an exciting, involving, yet neutral sound. Going to bypass (on those recordings with enough output to permit it) did, however, cause a (previously noted) reduction in dynamics. Normally that would get my suspicions flowing. Was the high-level stage exaggerating dynamics? Or was some unaccounted-for matching problem (remember impedance mismatches?) compressing apparent dynamic shadings in the direct mode? Frankly, I was enjoying the reproduction too much to agonize over the point too long.
The PS Audio 4.6, in comparison with the Athena, was a bit more subdued through its high-level inputs, unbypassed. It didn't have the overall thrust and drive of the Sumo preamp. Yet it was slightly sweeter, equally detailed, and just a bit more three-dimensional. When the PS's optional M-500 power supply was added, it was a different story, the PS becoming nearly as dynamic, more open, and with noticeably more depth. But we're talking almost twice the cost here. Used with CD input, the Athena is a strong contender for top honors in the budget preamp sector.
There was, it turned out, a noticeable drop-off in my enthusiasm for the sound of the Athena through its phono stages. My initial impressions, using the Grado into the phono stage at the low-gain setting, were reasonably favorable. On Ojebokoren/Cyndee Peters (Opus 3 77-04), the overall sense of space, balance, and soundstaging were satisfying, although I did note some loss of the three-dimensionality and depth which I know to be on this recording. Percussive bass and bass guitar (Professor Johnson's Astounding Sound Show, Reference Recordings RR-7, and Three-Way Mirror, Reference Recordings RR-24, among others) were deep, solid, slightly but not excessively warm, and convincing. But I did note, on program material with significant high-frequency energy, a small but noticeable degree of grain causing a slight smearing of the extreme high frequencies, combined with some forwardness and "etching" in the lower treblethe brightness region.
I also noted some reduction in what other reviewers have dubbed "intertransient silence," a term used to describe the gaps between transientsthe brief flashes of silence and near silence which might almost be called "anti-transients." The partial "filling-in" of these spaces reduces transparency and focus, subtly obscuring the fine details necessary for a fully three-dimensional soundstage, and flattening perspectives. The Athena's shortcomings were not severe in the context of a moderately priced preamp, but were nonetheless evident on careful listening and comparison with at least one other competitive product, the PS Audio 4.6. The latter was itself bettered by the Klyne SK-5A in all these parameters, although I felt the PS to be closer to the Klyne than the Sumo in the quality of its high-level phono input.
Much of the above listening was done using the PS Audio 200Cx power amp. This didn't seem entirely fair to the Sumo since the PS preamp might be expected to perform synergistically with the 200Cx. A Sumo Polaris was on hand and was pressed into service to cross-check the results. Although the Polaris slightly softened the extreme top end and was itself not as transparent as the more powerful, expensive 200Cx, in general the overall results were similar.
A Motif MS100 driving a pair of VMPS Tower II/Rs was also thrown into the mix (it had been used for much of the CD listening). This combination softened the brightness region (the VMPSes are a bit laid-back there), and slightly sweetened the high end. But still my conclusions were not substantially altered: the standard phono gain stage of the Athena is competent, listenable, and of reasonable quality for the price, but its limitations ultimately got between me and the music.
The moving-coil stage of the Athena, using the Dynavector 17D pickup, had a character very similar to the lower-gain phono input, allowing for cartridge differences of course. Noise levels were very low, the sound lively and open. Lateral imaging was excellent, but some reduction of depth was noted (though some depth remained on recordings with significant amounts to begin with). Overall balance was slightly warm through the bass and midbass, albeit with good low-end weight, and was a bit etched (though not hard) at the top. The limitations noted in my comments on the high-output phono position were no worse than before, but my feelings about them remained.
Moving-coil performance was, overall, very respectable for a preamp at this price, but well removed from the open, transparent, three-dimensional character of high-end, generally high-priced competitors. An extensive comparison with the PS Audio 4.6 with its standard power supply proved more to the point. Neither struck me as truly transparent and neutral with a moving-coil pickup; the PS erred in the direction of softening and rounding, the Athena was more sparkling and open but also somewhat Technicolored. The 4.6 can be upgraded with the add-on M-500 power supply ($495 extra), which definitely puts its moving-coil stage into the big leagues. The Athena is strictly come-as-you-are.
My conclusions about the Athena are mixed. The Sumo preamp is an excellent, exciting performer with CD. For those concentrating on venerable vinyl, the Athena strikes this reviewer as a competent performer in its price class, except for a few nagging shortcomings that kept me from the enthusiasm its CD sonics seemed to warrant. The Sumo is well-made and -finished, has a reasonable balance of strengths between its low-level and high-level phono stages, and a truly notable high-level line stage. But it didn't push all the right buttons for me. None of its phono-stage failings were extreme, certainly not at the price, but it had the misfortune to be reviewed concurrently with a close competitor which was significantly free of those failings.
Some of you who are building your systems around CD are going to do back-flips when you hear the Athena. With an improvement here and there in the phono stages, the rest of us might join you. But not yet.
Footnote 1: Also note my comments in the PS Audio 4.6 review on possible impedance impacts caused by bypassing in the output stage, a particular problem with long interconnects. I did not encounter this problem with the Athena.