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Yamamoto A08s ($3,200) - original review: The A08s was one of three power-only components in this comparison (the Gryphon Diablo being an integrated) and was used with the Zu Mother power cord and ASI unbalanced interconnects from the Wyred4Sound STP SE preamplifier whilst sitting on the ASI HeartSong amplifier stand without Isolpads. My A08s is equipped with Emission Labs 45s instead of the stock Cunninghams but all the other tubes are stock.

The A08s was the only SET in this exercise and its mighty 2 watts into 8 ohms obviously put it in a different category. It was indeed the most "different" of the four yet far less than anybody might expect.

FirstWatt F5 ($3,000) - original review: The F5 is the amplifier that preferred being on the floor sitting on Isolpads. Not that sitting on the HeartSong rack sounded bad at all but transients were sharper and resolution slightly higher on the pads than on the rack (both combined were too much, turning to zingy treble). I ran the F5 with a Zu Bok power cord and ASI unbalanced interconnects. At 25 watts into 8 ohms it is still a low-powered amplifier but far more useable than the A08s.

Genesis GR360 + MDHR ($13,000) - original review: The Genesis incorporates a built-in rack and suspension so I used it simply resting on the floor connected to the STP SE via a 1.5m run of balanced LiveLine cables (my version of the GR360 only accepts balanced connections to couple directly to the balanced Hypex modules though a single-ended version is also available). The GR360 used here differs from the one I reviewed a couple of years ago in small yet very significant ways. First and foremost I am running the brand-new transformer developed by Genesis to address the slight hum issue of the original transformer (a low-level mechanical buzz that did not make it to the speakers yet in small rooms could be heard if sitting close the transformer). The new transformer is also slightly more powerful and seems a little more open and resolving (slightly but Gary Koh agrees with me on that). A second difference is that I replaced the Isotek power cord provided by Genesis with a Zu which removed the last bit of dynamic restraint. Finally I also rested the transformer on Isolpads which seemed to add a little bit of internal resolution. The last two changes are not revolutions but when we get to this level of performance, every little bit of fine tuning helps. Everything combined turns the GR360 + MDHR into a very powerful, articulated and dynamic amplifier that’s more resolved, open and fluid than the original.
Gryphon Diablo (€11,500) - original review: The Diablo integrated obviously did not require the use of a separate preamplifier hence the STP SE was omitted and the Esoteric X03 SE connected directly via balanced ASI LiveLine interconnects. I used a Zu Mother power cord (the same I used during the whole review period) and sat the Diablo on the HeartSong stand without Isolpads as that's how it sounded best to me. The Diablo delivers 250 watts into 8 ohms, making it the most powerful machine of the four tested and also the heaviest. Moving the Gryphon on and off the rack made it a painful proposition at the end of the day.

I tried to make the rest of the system as resolved, transparent and revealing as I could as I anticipated differences to be minor at best. I relied exclusively on the Esoteric X03 SE as source with ASI LiveLine power cord and when the STP SE preamp was in use, it too was powered through a LiveLine cable. Speaker cables were Franck Tchang as well. This system description would not be complete without acknowledging the Zu Essence speakers. It does take a very special speaker to be able to operate with amplifiers from 2 to 250 watts. I won't pretend that the Essence is a perfect match for all these amps. As we'll see in the listening notes the A08s was at time a little stressed and would have probably preferred speakers in the 101 to 104dB/watt range rather than 97dB but sound level was never an issue even with the Yamamoto. At the other end of the range, the Genesis has been designed for speakers with higher current needs and likely does not fully stretch its legs with the Zus (although with the MDHR the difference is close to gone). The Diablo and F5 seemed to be in heaven driving the Zus but obviously all four amps would probably have preferred speakers with a little more resolution and finesse in the upper midrange/lower treble band. Though not perfect, all in all very few speakers I know could have enabled this direct comparison, with most of the other Zu models being less resolved in the treble and/or using active bass systems to mask most of the performance differences in that range.

The first track I will use for this comment & contrast exercise was Rebecca Pidgeon's "Spanish Harlem" from her album The Raven. I can't imagine a better track to showcase what the Yamamoto A08s is all about as Ms. Pidgeon's voice is recorded center stage with all the nuances she is capable of. You can hear her lips part yet the recording actually also renders a full-size recording studio with a warm and enveloping acoustic, supporting instruments in the background while being extremely resolved and nuanced. It is a masterpiece of naturalness with extreme resolution. There’s no better way to put it and no better way to listen than through the Yamamoto A08s. The triode on this record does what triodes do best. It creates a large scene, showcases the voice in all its splendor and wetness without taking anything away from the instrumental background textures (which here are just a few instruments, not a massive orchestra).