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
- 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
- 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
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
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.
- Frequency Response of Output Voltage as a Function of Output Loading
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
(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
|Chart 3 - Distortion
as a Function of Power Output and Frequency
8-ohm output loading
Cyan line: 100W
Blue line: 30W
Magenta line: 10W
Red line: 1W
|Chart 4 - Damping Factor
as a Function of Frequency
Damping factor = output impedance divided into 8
|Chart 5 - Distortion and
1kHz signal at 10W into an 8-ohm load