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POSITIVE FEEDBACK ONLINE - ISSUE 23
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pathos acoustics

Logos integrated

as reviewed by Lester J. Mertz

 

 

 

 

LESTER J. MERTZ'S SYSTEM

LOUDSPEAKERS
DIY - 1. LJM Originals, Transmission Line w/ Dynaudio 17W75 and Morel MDT30, 2. LJM Modified, BK16 – folded horn w/ Fostex FF165K and Peerless Soft Dome, 3. LJM Originals, Floor Stander, w/ Vifa P17WJ and Vifa DX25SG, 4. LJM Modified, Dynaudio "Aries" – (currently on loan to Tim Stant), and 5. LJM subwoofer, w/ Audio Concepts AC12.

ELECTRONICS
Blue Circle BC21.1 preamplifier, Linn phono stage, and Sonic Frontier Power 1 (55w) with Svetlana's 6550c Output, and 6N1P Drivers, B&K ST 140 (105w), and Sound "Valve 110 SE" (on loan from Fred Kat) amplifiers.

SOURCES
Arcam CD 33 T, Linn LP12, Grace 707, Signet Mk 110 E (mc) into Monolithic PS 1.

CABLES
Audience Au24 (on loan from Keith Oyama), Ridge Street Audio Design, "Poiema!!", DH Labs Air Matrix, DH Labs Silver Sonic, LJM, RS microphone, Maple Shade Double Helix, Synergistic Research Active Looking Glass, van den Hul The Second, van den Hul D300 Mk III Hybrid interconnects. van den Hul D352 Hybrid speaker cables. Blue Circle, BC02, Kimber Kord, Synergistic Research, Active, AC Master Coupler, and LJM Originals, Marinco Plugs w/Belden 14-AWG AC cords.

ACCESSORIES
Acme Audio Labs, cryogenic treated outlets and Hubbell, outlets, Mod Squad Tip Toes and cones, Mana Sound Frame, FIM 305 (roller balls), Vibrapods, Maple Shade Iso-Blocks, Maple Shade Maple Boards, Marchland XM9 electronic crossover, Boos Blocks, Rock Maple Granite Slab, Target Stand TTSA5, LJM Wood Blocks/Equipment Stands, VPI 16.5 (record cleaning machine).

The Logos is a big, powerful integrated amplifier with a tube input stage (one 6922 per channel) followed by a dual-mono solid-state output stage rated at 110 watts into 8 ohms (220W into 4 ohms). Solid-state guys are probably getting bored already, but hey, don't  despair! This amp plays really big. I compared it to two solid-state amps, the B&K ST140 (105W) and the NAD 3140 (100W), and the Logos sounded way more powerful. This may be due to the fact that (according to the manufacturer) the amp can deliver high current into demanding loads, but output current ratings were not supplied.

The Logos drew immediate attention from guests. Their remarks ranged from a simple "Wow!" to "It's really beautiful, and I'll bet it's really expensive!" One visitor said that it was the most beautiful integrated amplifier on the market. After listening, everyone had something positive to say, and while some still felt it was expensive, if you were to use separates that reached the Logos' level of performance, you could easily blow right past its $4800 price, and you would need twice as many expensive interconnects and power cords to hook them up.

One of the joys of using the Logos is that everything is so well thought out. The simple, all-metal remote has just four unmarked buttons: volume up, volume down, input selection, and mute. You can navigate through a complete listening session without a worry. When the amp is turned on, there are some audible relay clicks as the startup sequence begins. After about a minute, the central LCD glows and indicates zero volume level —the amp returns to zero volume level each time it shuts down. You can ramp up the volume via the remote or by turning the chrome central knob, which uses a logic circuit with a small time delay. The company does not recommend leaving the amp on all of the time. I tried leaving it on for an entire weekend, and thought I heard a slight compression of dynamics after 36 hours or so, but I didn't repeat the test to confirm my impression.

Selecting one of the seven inputs (two balanced and five RCA pairs) is intuitive. When you press the input selection button on the remote, the amp magically changes to the next one in line. I say "magically" because there is absolutely no noise, or any other indication that something has transpired, other than the LCD number changing. Comparing interconnects couldn't be easier—just run the two pairs into succeeding inputs and use the remote to switch between them. If you're not the one doing the switching, you won't know when the change takes place until the sound changes. I found that the tube input circuit to be highly tolerant of interconnect changes, as they produced only subtle differences. The output circuit was not as forgiving, and changes in speaker cables were easily discernible. With my speakers, I got the best results from heavy gauge (10 AWG) van den Hul cable. Differences in power cords were also easy to hear. The supplied cord was fair, but revealed background noise at moderately high volume settings. More expensive cords eliminated the noise completely, possibly because of better shielding?  

Almost everyone responded to the Logos with comments like, "I've never heard that before, and I've played that recording a hundred times!" or "This thing is in another league." The Logos is a zero-feedback design, which is very unusual for a solid-state amplifier. SET listeners have been saying all along that it is primarily the power amplifier's feedback circuit that kills nuance and detail in recordings. They may be right, because the Logos delivers detail on a par with any amplifier, of any kind.

For me, the most impressive attribute of the Logos was its bass. I've heard SETs that match the resolution of the Logos, but none that match its bass performance. The word here is control. Speaker systems interact with the amplifiers in different ways. Sealed and transmission-line loudspeakers are generally benign in their impedance swings compared to the tuned-port (reflex) boxes that most of us listen to. Reflex speakers, with their huge double impedance humps—often rising up to five and six times the rated impedance in the bass— can confuse an amplifier's output circuitry, but the Logos simply doesn't flinch. It drives the speakers with powerful bass that is cleaner and more pure than that of any amp I've heard on the low side of $10K. Its bass is believably realistic, and that's saying a lot.

The Logos invites you into all types of music, loud or soft, large groups or single performers, but (and I'm not exactly sure why this is) with anything Italian, it is pure magic. Am I overusing the word "magic"? Maybe, but it conveys the feeling I get when I listen to my system under the grip of the Logos. Perhaps "enchanting" is a better word. It certainly describes Cecilia Bartoli's An Italian Songbook (London 455 513-2) with James Levine on piano. She never sounded better! Or "mesmerizing," which describes Peter Blanchette, on Archguitar Renaissance (Dorian 93178), with the Virtual Consort (overlays) and Charles Schneeweis (brass instruments). Get this album if you love guitar, or if you love 14th and 15th century music. It just bubbles along, with superb energy that locks you in your chair. Or how about "compelling," which applies to Giuliano Carmignola on Vivaldi—Late Violin Concertos (Sony Classical SK 89362,) playing with the Venice Baroque Orchestra. His energy came through on every cut. Great stuff!

Like every other audio component, an amplifier is a series of design compromises. Every designer has his own goals, and sometimes one aspect of performance is sacrificed for another. If there is a fly in the ointment with the Logos, it is strings. Strings can be difficult to capture on any system, but especially with solid-state amplification. I may be getting a little picky, but the sweetness of real strings is noticeably diminished by the Logos. Perhaps only a tube amp can get you closer to the wonderful sweetness of the real thing. Is it the forgiving harmonic distortion of a tube circuit, versus the more discordant distortion of a solid-state amp? You'll have to decide for yourself. Maybe it's just what I've gotten used to. If you don't listen to classical music, you can dismiss my comment about the Logos' string sound, because you probably won't hear it.

If you are looking for an amplifier gear in the Logos' price range, or close to it, you must hear this amplifier. The Logos might be the standard by which you judge every other amp. It also might be the ultimate integrated amplifier for real-world audio systems. Les Mertz

  • Output power: 110W RMS @ 8 Ohm, 220W RMS @ 4 Ohm

  • Frequency response: 2Hz-200KHz ±0,5dB

  • THD: <0.05%

  • S/N ratio: >90dB

  • Input impedance: 100 KOhm

Logos integrated
Retail: $4795

Musical Surroundings
web address: www.musicalsurroundings.com

 

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