All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Notes: Measurements were made at 120V AC line voltage with both channels being driven (stereo mode). Measurements were made on the left channel unless otherwise noted. The Audio Precision AUX-0025 measurement filter was used unless otherwise noted.

### Power output (stereo mode)

- Power output at 1% THD+N: 63.6W @ 8 ohms, 106.7W @ 4 ohms
- Power output at 10% THD+N: 84.7W @ 8 ohms, 137.8W @ 4 ohms

### Power output (mono mode)

- Power output at 1% THD+N: 231.3W @ 8 ohms, 366.7W @ 4 ohms
- Power output at 10% THD+N: 289.0W @ 8 ohms, 476.0W @ 4 ohms

### Additional data

- This amplifier does not invert polarity.
- AC-line current draw at idle: 0.17A, 0.42PF, 8.6W
- Gain: output voltage divided by input voltage, 8-ohm load
- Stereo mode: 17.2X, 24.7dB
- Mono mode: 34.7X, 30.8dB

- Input sensitivity for 1W output into 8 ohms
- Stereo mode: 164.4mV
- Mono mode: 81.5mV

- Output impedance @ 50Hz
- Stereo mode: 0.012 ohm
- Mono mode: 0.027 ohm

- Input impedance @ 1kHz

- Stereo mode, Lch/Rch: 8.2k ohms, 46.3k ohms
- Biwire mode, Lch/Rch: 8.2k ohms, 8.2k ohms
- Mono mode: 8.2k ohms

- Output noise (stereo mode), 8-ohm load, unbalanced inputs terminated with 1k ohms, Lch/Rch

- Wideband (no AUX-0025 filter): 1.08V/0.88V, -8.9dBW/-10.1dBW
- Wideband: 1.54mV/1.40mV, -65.3dBW/-66.1dBW
- A weighted: 0.058mV/0.072mV, -93.8dBW/-99.1dBW

- Output noise (mono mode), 8-ohm load, unbalanced inputs terminated with 1k ohms

- Wideband (no AUX-0025 filter): 1.76V, -4.1dBW
- Wideband: 1.72mV, -64.3dBW
- A weighted: 0.086mV, -90.3dBW

### Measurements summary

The Calyx Femti is a stereo power amplifier of moderate output that uses a bridgeable ICEpower 125ASX2 switching amp preceded by a custom input buffer and input-switching circuit board. The switching amp is the lowest-powered of the three available ICEpower models.

Because the Femti can be switched from stereo to bridged-mono mode, measurements were taken in both modes. In the accompanying charts, the suffix “A” denotes a measurement of bridged mode. In the third mode, biwiring, in which the two stereo channels are both fed the same input signal, is no different from the performance in stereo mode, except for a peculiarity of the input impedance (see data above).

Charts 1 and 1A show the frequency response of the Femti with varying loads. The amount of switching carrier noise in bridged mode prevented getting a good measurable response without the Audio Precision AUX-0025’s external filter, so to get compatible responses in the stereo and bridged modes, the filter was used in both cases. There is a bit more noticeable deviation of high-frequency response in bridged mode, with an earlier high-frequency rolloff and a bit more out-of-band high-frequency peaking.

Charts 2 and 2A illustrate how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE intermodulation test signals and amplifier output load for 8- and 4-ohm loads.

THD+N as a function of frequency at several different power levels is plotted in Charts 3 and 3A. High-frequency distortion rise with increasing frequency is considerable, and there is also a rise in low-frequency distortion with power. As can be seen, the apparent noise floor is somewhat lower in bridged mode, as the amount of distortion is lower in the midband.

The Femti’s damping factor vs. frequency, shown in Chart 4, is of a value and nature typical of many solid-state amplifiers: high up to about 1-2kHz, then rolling off with rising frequency.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal in stereo mode is plotted in Chart 5. The magnitudes of the AC-line harmonics are reasonably low, and the signal harmonics are low in amplitude. The 10W/4-ohm spectrum for the bridged mode (not shown) looked about the same as in Chart 5.

### Chart 1 - Frequency response of output voltage as a function of output loading

Stereo mode

Red line = open circuit

Magenta line = 8-ohm load

Blue line = 4-ohm load

Cyan line = NHT dummy-speaker load

Chart 1A

Mono mode

Red line = open circuit

Magenta line = 8-ohm load

Blue line = 4-ohm load

Cyan line = NHT dummy-speaker load

### Chart 2 - Distortion as a function of power output and output loading

Stereo mode

(Line up at 20W to determine lines)

Top line = 4-ohm SMPTE IM distortion

Second line = 8-ohm SMPTE IM distortion

Third line = 4-ohm THD+N

Bottom line = 8-ohm THD+N

Chart 2A

Mono mode

(Line up at 10W to determine lines)

Top line = 4-ohm SMPTE IM distortion

Second line = 8-ohm SMPTE IM distortion

Second line = 4-ohm THD+N

Third line = 8-ohm THD+N

### Chart 3 - Distortion as a function of power output and frequency

Stereo mode

(4-ohm loading)

Red line = 1W

Magenta line = 10W

Blue line = 20W

Cyan line = 70W

Green line = 100W

Chart 3A

Mono mode

(4-ohm loading)

Red line = 1W

Magenta line = 10W

Blue line = 50W

Cyan line = 200W

Green line = 400W

### Chart 4 - Damping factor as a function of frequency

Stereo mode

Damping factor = output impedance divided into 8

Chart 4A

Mono mode

Damping factor = output impedance divided into 8

### Chart 5 - Distortion and noise spectrum

Stereo mode

1kHz signal at 10W into an 8-ohm load