Audio Dynamics/ADC CA-200E Integrated Amplifier Review

Since its recent reorganization and relocation from Massachusetts to California, Audio Dynamics Corporation (ADC) has announced a new line of distinctively styled audio components designed to be operated by a unified system remote control. Heading the ADC lineup is the CA-2000E integrated amplifier, which is rated to deliver 100 watts per channel into 8-ohm loads from 20 to 20,000 Hz with no more than 0.05 percent total harmonic distortion (THD). The CA-2000E also carries a 4-ohm FTC rating of 120 watts over the same frequency range with less than 0.1 percent THD.

Despite its deceptively simple and unadorned appearance, the CA-2000E is a full-featured integrated amplifier. The tone and balance controls are small, black center-detented knobs that contrast nicely with the dark-gray panel. The larger volume knob is turned by a motor during remote operation. Except for the small source/tape-monitor knob, the other controls are all pushbuttons. All control functions are clearly marked on the panel.

The CA-2000E has inputs for a tuner, a CD player, an mm or mc phono cartridge, two tape decks, and an auxiliary source. Each source-selector button contains a small red led to identify the program being heard or recorded. Smaller buttons activate the two sets of speaker outputs, the infra-sonic filter, and the loudness-compensation circuit. The direct button bypasses all switches and active circuitry between the CD inputs and the amplifier volume control, eliminating all filters, tone controls, and the muting function (a 30-dB volume reduction that can be selected only from the remote control). The front panel also has a stereo headphone jack.

On the rear apron is a button that switches the phono input between its moving-magnet and moving-coil modes. The phono and CD input jacks are gold plated, and the two pairs of speaker outputs are multiway insulated binding posts on 3/4-inch centers that are compatible with single or dual banana plugs as well as wire leads.

The circuitry of the CA-2000E was designed for optimum functionality rather than merely to create an impressive list of features. For example, the infrasonic filter has virtually no effect in the audible frequency range above 20 Hz, but it reduces the output by 29 dB at 4 Hz, where normal lp warps have their maximum effect and can overload an amplifier, creating intermodulation distortion. All inputs as well as the tape outputs are buffered to minimize leakage between sources and interaction with cable characteristics. The tone controls affect only their assigned frequency ranges, with no overlap or excessive sound coloration.

Even the remote control has been “beefed up”; it has three signal LED’s (one facing upward), so that the controller need not be pointed at the amplifier, nor is its useful range limited to a few feet. There is no power switch, however.

The exceptionally complete performance specifications of the CA-2000E indicate that it has been designed to drive almost any speaker load likely to be found in a home music system. This capability is illustrated by its impressive dynamic power ratings of 150, 225, and 325 watts per channel into loads of 8, 4, and 2 ohms, respectively.

The ADC CA-2000E measures 17 inches wide, 14-1/2 inches deep, and 4 inches high, and it weighs 22 pounds. Price: $799, including the system remote control.

Lab Tests

The top of the amplifier ran moderately warm in normal operation, and it became very hot during our preconditioning and high-power tests. During our high-power continuous-output measurements into 2-ohm loads, the protection circuits shut the amplifier down, and at one point the 6.3-ampere AC line fuse blew. Since these occurrences are unlikely when the amplifier is driving speaker loads, even those rated at 2 ohms, with program material, they do not reflect a weakness; rather, they provide a testimonial to its protection system.

The 1,000-Hz output clipped at 125 watts into 8 ohms, 196 watts into 4 ohms, and 295 watts into 2 ohms (the first two measurements were made with both channels loaded and driven, the last with one channel loaded by 4 ohms to avoid blowing the line fuse). At most listening levels, the 1,000-hz harmonic distortion was about 0.01 percent into 8 ohms, slightly less into 4 ohms, and 0.01 and 0.02 percent into 2 ohms.

Through much of the low- and mid-frequency range, the distortion was 0.0025 to 0.005 percent at power outputs from 10 to 100 watts. It rose at higher frequencies to a maximum of 0.02 percent at 20,000 Hz and 100 watts output. The amplifier’s slew factor exceeded 25, and it was stable with reactive simulated speaker loads.

The sensitivity (for a 1-watt reference output) was 15.5 millivolts (mv) at the high-level inputs, 0.27 mv for MM phono, and 0.024 mV for MC phono. The respective A-weighted noise levels (referred to 1 watt) were —83, —80.4, and —79.2 dB. The mm phono input overloaded at levels from 110 to 130 mV over the 20- to 20,000-hz range. The input’s impedance was 47,000 ohms in parallel with 140 picofarads.

At the maximum settings of the bass and treble controls, the response was down 3 dB at about 180 and 4,000 Hz, respectively, providing ample control at the frequency extremes without affecting the midrange response. The basic frequency response, with the tone controls centered, was flat within ±0.2 dB from 20 to 20,000 Hz. In the CD-direct mode, the response was flat within 0.05 dB from 10 to 12,000 Hz and down 0.25 dB at 20,000 Hz. The infrasonic filter raised the output at 20 Hz by about 0.25 dB and cut the output off sharply below 15 Hz, to about — 6 dB at our low-frequency measurement limit of 10 Hz.

The loudness compensation boosted only the frequency range below 200 Hz, to a maximum of 9 dB at 20 Hz. The maximum boost was obtained at all volume-control settings below —20 dB, so that further reduction of the control setting had no additional effect on the frequency response.

Comments

The ADC CA-2000E performed to perfection in our music system. Its understated styling and simplified controls did not limit its operating flexibility in the least. And even though the amplifier can do just about anything one might wish in an advanced audio system, its operation is largely intuitive.

The dynamic power capability of the CA-2000E, especially into 2-ohm loads, gave it the ability to play very loud with almost any speaker without sounding strained or placing the speaker in jeopardy. We never drove the amplifier to clipping in our listening tests because the sound was becoming uncomfortably loud (but still clean) before we reached that point.

Given the ideal characteristics of the infrasonic filter, we chose to use it at all times. Leaving the filter on gave us the freedom to boost the bass to any degree without risking damage to the speakers or audible distortion. Both of the CA-2000E’s tone controls had excellent characteristics as well, among the best we have used. They did not significantly degrade listening quality even when set at their limits.

Finally, the remote control lived up to its promise. Used anywhere in the same room with the amplifier, and pointed in any direction, it never failed to operate properly. Overall, the CA-2000E is a very fine product and represents an auspicious new beginning for Audio Dynamics.

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