Teramoto Feastrex CV4055

In my strange little corner of the hifi world, Feastrex is a name that is almost Divine. Founded in 2005 by Yukihito Akiyama, Feastrex is a Japanese brand famous for making some of the most exotic, highest performing full range drivers and speaker systems in the world. Their low production, handmade, almost bespoke drivers exude quality and craftsmanship, and they seem to promise an ability to render the natural sound of music in your space.

One thing that I immediately think of when I think Feastrex is, unfortunately, price. They are simply beyond my means for now. But I like to window shop as much as anyone, and I’ve been looking at them for years. They very rarely come up on the used market; I can think of only 2 or 3 used sales that I’ve encountered over the years, which really does tell you something. With a line of patented “Naturflux” magnet, alnico and yes-even field coil drivers, as well as custom enclosures to match, all hand-built to the highest standards, Feastrex has something to offer for both the DIY community as well as the more mainstream audiophile.

So when this beautiful Finemet-loaded CV4055 amplifier came up for sale from Rich at Treehaus Audiolab, who has been a friend of this site for some time, I snatched it up without hesitation. Before seeing this amp I had no idea that Feastrex even made an amplifier, but it turns out that they have a few models, optioned exclusively for those who purchase their speakers. Much like Ferrari requires you to own a few before you are “qualified” to buy certain models, Feastrex makes an amp that is only intended for owners of their speaker. In Feastrex’s case it makes sense; they design the amplification that best suits their speaker, assuring the owner gets the most out of the complete package. But of course that makes these amplifiers quite rare indeed.

And what a fine and unusual amp it is! Designed by Haruhiko Teramoto, the master craftsman of Feastrex’s driver range, these beautiful amplifiers are understated and functionally simple. Assembled on the typical Japanese folded metal chassis, they are loaded with a complete set of Finemet iron! An on/off switch, muted red light and smooth action volume control are all of the controls offered. Perfection. The rear panel hosts what I assume are 4, 8, and16 ohm taps (they are unlabeled) and an IEC connector, allowing an aftermarket power cord. My unit is made for the Japanese market and is 100 volt, so I’m using a step down transformer, which lately has become the norm in my single ended room.

I must admit that I had some very high expectations for this amplifier. And it is a superb performer, as should be expected. The Feastrex CV4055 amp sounds thick and meaty, but is still detailed and dexterous. Being a push pull design, I expected a push pull sound. And although it does deliver the somewhat more dynamic and driven presentation that I most associate with push pull amps, this one still has the aura and delicate detail retrieval that I hear mostly in single ended amps. This is an amp that does not shy away from the bass, grabbing my Rullit and Coral drivers with an iron fist! In fact it provides a somewhat bass heavy presentation that challenges some of the more lightweight wide-band drivers in my stable. Once warmed up it is a real treat to listen to, and it compares well with any of the upper tier of the 100+ amplifiers that have passed through my room in the past 20 years.

If I had to choose one word to describe the Feastrex CV4055 it would be “solid”. This amp has a grounded feeling and it grips the speaker with authority. It puts out around 8 watts of power, so a little more than most of the small amps I play with. I feel like my Rullit drivers really respond best to small wattage amps; too much power is not such a good thing. In this respect the Feastrex is sort of at an ideal higher-power loading for the Rullits. It can play LOUD! And without distortion.

Compared to the biggest imagers I’ve experienced, the image thrown by the Feastrex appears somewhat narrower. While some amplifiers present a spread out soundstage, with placements well beyond the speakers, on the CV4055 I feel like I’m looking down a wide cone rather than a spread out field. Its still an immersive experience, if the recording has it the players appear seamless and together, but a little narrower than I have become used to. In a way, the spread out field can feel disconnected, while the cone view of the CV4055 is more whole and together. Perhaps that’s part of the “solid” feeling in its presentation.

I do feel a certain hardness in the Feastrex amp that is not what I expected. This is a quality that I used to enjoy but have been moving away from in my preferences, and its evident going from the Feastrex amp into my extremely relaxed sounding Alpa 300B monos or Lance Cochrane’s push pull EL84, which is more of an apple to apple comparison. The Feastrex does bass better than either of those candidates, and sounds thicker and meatier, but over time they both make me relaxed in a way the Feastrex doesn’t. I encountered this same feeling from the amazing OTL-1 from Roger Modjeski. The Feastrex (and the OTL-1) are amps well suited to active listening, and less so as background, go-about-your-day solutions. Like in Geology, there’s a hardness scale in audio, and while not quite the Diamond that the OTL-1 was, the CV4055 is at the harder end of the scale. A bit like the often-strident type 10, versus the more relaxed 45.

To date I’ve used this amp with my Rullit Aero 8, Isophon PH2132, Jensen C855, Coral 10CX-50 and 8A-70. It has matched well with all of them, although the somewhat fragile Jensen is working hard on all that bass energy! I would love to hear this amp mated with one of its intended Feastrex drivers and discover if it’s an even better match there. We’ll see what the future holds. For current and future Feastrex owners who are curious, I think this could be a great solution. The CV4055 amplifier is simple in operation and sounds excellent. It has plenty of power, and is very well made by people who really care and who have used literally some of the best parts on Earth. The amp provides a bass response that will make the most of any driver. It’s also a standalone no-preamp-required solution, which to me is a huge plus in flexibility. And presumably, being designed by the master himself it will be a perfect match to a Naturflux driver. My time with the CV4055 has been a fun and enlightening experience. Rarely do you encounter such a no-holds-barred, purpose driven instrument. Recommended if you are lucky enough to find one of these exotic and unusual amplifiers.

Simple, clean and elegant. An austere but functionally simple Japanese build with the highest quality parts. What a treat!

The CV4055 is a British video tube dating to the early to mid 1950's, here by Brimar. I do love TV tubes and apparently so does Teramoto -san. The input tubes are CK-5755 made by Western Electric for Raytheon (WE 420A), and are somewhat similar to the 12AX7 with a different pinout.

That's a lot of Finemet transformers! Finemet is a new invention, developed by Hitachi. It’s a nanocrystalline material that has a much lower core loss compared to more traditional materials and represents the very top of the line for tube audio in the 21st century. Apparently the Finemet transformers were added gradually to these amps, beginning with output transformers only but with later models like mine expanding to a full compliment.

The tape wound transformer is a strange look, giving this amplifier a very Frankensteinian laboratory vibe. It calls to mind the work of the late John Hogan, albeit in a much cleaner build.

One thing I’ve noticed is that this amp sounds quite different depending on the tap used. Some amps really don’t sound much different from 16 to 8 ohm, but this one changes audibly.

Somehow this is one of the most satisfying volume controls I’ve used. The placement is perfect and the taller dial they chose fits my hand well. Its smooth in action and glides gently up the volume ladder. I can use the whole dial, unlike 75% of the amps that come through my room. Like Goldilocks, this one is just right. After all of the gear that's rolled through my room, I often find its the little things like this that really matter to me.

Here with some competition. Lance Cochrane’s EL84 is a little brighter, and I’m running Siemens power tubes so they are contributing some to that brightness. The CV4055 are different. I hesitate to say darker, but “more solid” feels right. The Alpa 300B are a very different flavor, more open and relaxed, and a bit more intimate.