Calyx Femti Amplifier

The Calyx Femti is a dimunitive power amplifier that is a visual match for the 24/192 DAC. It's aluminium unibody chassis is finished in black with an artistic rendition of a G and F clef engraved on the top cover.

The rear panel is quite cramped and includes two pairs of high quality binding posts, a set of single ended inputs and a rotary selector switch to operate the Femti as a normal stereo power amplifier, a dual output mono amplifier (for a biwired speaker), and a bridged mode mono amplifier. Very much like the Femto DAC, the power switch for the Femti is discreetly located on the side (right hand side vs. left hand side for the Femto). An IEC outlet permits use of after-market power cords.

The Femti delivers 125 watts per channel into 4 ohm loads (and presumably half of that into 8 ohm loads), and 500 watts in bridged mode operation. A tricolour LED indicates normal operation, short circuit, and overload conditions. Not much information is provided about the technology used in the Femti, but I would not be surprised that this amplifier is powered by a B&O ICEPower module - I recall seeing the three LED indicators in a technical manual for ICEPower modules.

A close-up view of the offending binding posts - spade users beware

Ergonomically, I dislike two things about the Femti. The first are the binding posts which are shrouded. A downward facing slot allows insertion of spades from the bottom, but this is generally impossible with large gauge or stiff speaker cables. Eventually, I had to either evaluate the Femti with its chassis all the way at the rear edge of the rack (to allow the cables to trail downwards), or with the Femti elevated by tall footers to provide necessary clearance for the cables. This could have been easily solved by having the slots face upwards.

The second issue I have is the rotary selector switch. This can be easily rotated by accident (especially when you are busy trying to manipulate cabling at the rear), and could damage the amplifier if this is done while the amplifier is in operation. A recessed switch would have been more appropriate.

This unit is on dealer loan and I was quite worried about its initial performance. It was passed to me with about 50-75 hours under its belt. While it was pleasing, it also had a laidback and smooth character which tended to obscure low level detail.

I ran it continuously for an additional 48 hours, powering my KEF LS50 speakers with a burn-in signal. The chassis became slightly warm after extended use, and could probably be left powered, for long periods of time.

I paired the Femti with my Conrad Johnson ET-3SE or Sun Audio SVC-500 tube preamps, or drove it directly from my Antelope Zodiac Gold DAC. The Antelope has a relay controlled resistor network to adjust output levels. I was pleasantly surprised to hear the Femti essentially take on the character of its upstream partnering equipments. Both the Conrad Johnson and Sun Audio offered a fuller and more liquid perspective, while I felt that the Zodiac Gold connected directly to the Femti, offered the highest degree of resolution.

The Femti proved to be quite sensitive to power cords too. Pairing the Femti with an Oyaide Tunami terminated with Oyaide P/C-046 plugs resulted in a rather flat and bland presentation. A switch to a Nanotec Golden Strada 305 terminated with Oyaide P/C-004 was pleasing, but harmonically too sweet and polished. The Femti was eventually matched with an Acrolink 6N-4030 terminated with Furutech FI-28(R) connectors.

The Femti was very comfortable driving my Focal Diablo Utopia and KEF LS50 speakers. However, the match with my Thiel CS2.7 was less than ideal, with a noticeably strain and loss of control at louder volumes. I would keep the pairing to more sympathetic loads.

Detractors of Class D amplifiers should listen to the Femti. Tested blind, I doubt that they would even be able to correctly identify the Femti as a Class D amplifier.

Sonically, the Femti is quite neutral. It avoids the one-note bass I have heard from some early ICEPower models, while retaining excellent bass control. My LS50 especially appreciated the tightness and extension afforded by the Femti.

Midrange is smooth with a slight hint of creamy richness. Female vocalists are portrayed with a richer and less sibilant presentation. This slightly laidback quality provided for fatigue free listening, and a tendency to flatter poorer recordings. However, on the downside, some low level detail such as the texture and vibrato from singers such as Kit Chan is not as prominent.

The top end is extended and well-behaved. Percussion instruments are crisp and clear, with good strike and decay from cymbal strikes.

The Femti projects a wide soundstage, with above average depth.

Compared to my Conrad Johnson duo, the Femti did not project as deep a soundstage, nor render acoustic space as well. However, the Femti had the edge over my glassware in bass control, background blackness, and instrument separation.

To sum it up, the Femti is a competent performer in a compact package. Much of its performance depends on how you will handle volume control duties. I think this leaves the Femti in a rather awkward position. Much of its competition are able to offer at the Femti's price point, similar functionality and volume control in one package. However, I still think the Femti is worth a listen provided you are able to accept it's ergonomic short comings, and carefully plan your system.

A word of thanks to Audio Basic for their loan of the review unit.

Audio Basic

1 Coleman Street
#04-27, The Adelphi
Singapore 179803
Tel : +65 6338 3245
E-mail : audiobasic_sg@yahoo.com.sg