December 2008

Classé Audio Delta CA-2100 Stereo Amplifier: Measurements

All amplifier measurements are performed independently by BHK Labs. Please click to learn more about how we test amplifiers there. All measurement data and graphical information displayed below are the property of SoundStage! and Schneider Publishing Inc. Reproduction in any format is not permitted.

• Measurements were made at 120V AC line voltage with both channels being driven.
• Measurements made on left channel unless otherwise noted.
• This amplifier does not invert polarity.
• AC line current draw at idle: 1.0A.
• Input impedance @ 1kHz
• Unbalanced inputs: 150k ohms.
• Balanced inputs: 73k ohms.
• Output impedance at 50Hz: 0.004 ohm.
• Input sensitivity: 98.9mV.
• Gain (8-ohm load): 28.6X, 29.1dB.
• Output noise, unbalanced inputs, 8-ohm load, 1k-ohm input termination, Lch/Rch:
  • Wideband: 0.28mV, -80.1dBW / 0.27mV, -80.4dBW
  • A weighted: 0.068 mV, -92.4 dBW / 0.066mV, -92.4dBW
• Output noise, balanced inputs, 8-ohm load, 600-ohm input termination, Lch/Rch:
  • Wideband: 0.28mV, -80.1dBW / 0.29mV, -79.8dBW
  • A weighted: 0.066mV, -92.4dBW / 0.065mV, -92.8dBW

Power output with 1kHz test signal

• 8-ohm load at 1% THD: 116W
• 8-ohm load at 10% THD: 165W
  
  
• 4-ohm load at 1% THD: 211W
• 4-ohm load at 10% THD: 312W

General

The Classe CA-2100 is a medium-power solid-state stereo power amplifier, the lowest-powered unit of two stereo units in the CA product line.

Chart 1 shows the frequency response of the amp with varying loads. The high- frequency response is wide, with an approximate -3dB point of 160kHz. Output impedance as judged by the closeness of spacing between the curves of open circuit, 8-ohm, and 4-ohm loading is very low over the whole range. The usual NHT dummy load curve is not shown as the variations in the response would not show. The variation with the NHT dummy load in the audio range is of the order of +/- 0.02dB -- a totally negligible amount.

Chart 2 illustrates how total harmonic distortion plus noise vs. power varies for a 1kHz and SMPTE IM test signals and amplifier output load. Instead of a steadily falling amount of THD+N as power is increased, as is the case for noise dominated THD+N and/or crossover distortion, this amplifier has the noise dominated characteristic up to about 1W where the amount of THD+N stays constant up until clipping occurs. A small but real amount of actual distortion is being measured here over most of the power range.

Total harmonic distortion plus noise as a function of frequency at several different power levels is plotted in chart 3. When, as is the case here, the THD+N rises with increasing frequency and the amount of distortion in the 5-20kHz frequency range merges to the same amount for a wide range of power, it is generally indicative of a non-linearity characteristic that is second harmonic dominant and strongly frequency dependent.

Damping factor vs. frequency is shown in chart 4 and is of an extremely high value at low frequencies, and as is so typical of many solid-state amplifiers being high up to about 500kHz and then rolling off with frequency.

A spectrum of the THD+N residue of a 10W 1kHz test signal is plotted in chart 5. The magnitude of the AC-line harmonics is very low and simple, and intermodulation components of line harmonics with signal harmonics are absent here. Note the strongest test-signal harmonic being the second at 2kHz.

Red line: open circuit
Magenta line: 8-ohm load
Blue line: 4-ohm load
Cyan line: NHT dummy-speaker load

(line up at 1W to determine lines)
Top line: 4-ohm SMPTE IM
Second line: 8-ohm SMPTE IM
Third line: 4-ohm THD+N
Bottom line: 8-ohm THD+N

8-ohm output loading
Cyan line: 100W
Blue line: 30W
Magenta line: 10W
Red line: 1W

Damping factor = output impedance divided into 8

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

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