Classe Sigma AMP2 Solid State Stereo Amplifier in Box (2 of 2)


The Sigma series AMP2 is a 200W/Ch stereo amplifier utilizing switching technologies for both power supply and amplification stages.

A Classé-designed switch mode power supply with Power Factor Correction makes over 1,000W of clean and stable power available while being both compact and efficient.

A new class D amplifier topology provides wide dynamic range, smooth and extended frequency response and rich harmonic detail to yield stunning sonic performance.

The efficiency of class D adds efficiency, low heat dissipation and relatively small size to the list of the AMP2’s attributes.

Click here for an excellent Stereophile SIGMA review by Kalman Rubinson

Click here for a PDF copy of the SIGMA AMP2 Owner's Manual

(All tests un-weighted and 20Hz – 20kHz measurement bandwidth used.)

Frequency response
10Hz – 20kHz, -1dB into 4Ω

Output power
200W rms into 8Ω 400W rms into 4Ω

Harmonic Distortion
<0.018% @ 1kHz Balanced Input

Peak Output Voltage
116V peak to peak, 41V RMS no load
116V peak to peak, 41V RMS into 8Ω

Input Impedance
100kΩ Balanced / 50kΩ SE

Voltage gain
29 dB

Input level at clipping
1.4Vrms Balanced/SE

Intermodulation Distortion
>80 dB below fundamental into 8Ω Balanced

Signal to Noise Ratio
-100 dB at peak output into 8Ω (AES17)

Rated power consumption
177W @ 1/8th power into 4Ω

Mains voltage
100V - 240V, 50/60Hz

Overall Dimensions
Width: 17.00" (433mm)
Depth (excluding connectors): 14.57" (370mm)
Height: 3.75" (95mm)

Net weight
22.0 lb (9.97 kg)

Shipping weight
28.0 lb (12.70 kg)

The SkyFi Testing Process for Solid State Amplifiers:

We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and transistors are checked for signs of stress or damage.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally, we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If everything reads clean, we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier then remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will be also be tested.

Final testing involves pushing actual music thorough the amplifier. We've learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage Kef speakers that we're very familiar with which quickly reveal any discrepancies. Some amplifiers will then move into our listening room where they are tested with our in-house reference speakers of choice.

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.



Original Box







Yes - Power

Physical Condition


Working Condition


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