(Reprinted from the Summer 98 Audio Ideas Guide)

      Audio Research is known not only for its superb-sounding products, but also for its service, which is very important for a company that has made its mark with tubed products. Their CA50 is a tube integrated amplifier, the initial gain stages being a pair of of 6922s, followed by a driver stage using another pair of the same tubes, followed by a push/pull output using a matched pair of large 6550C tubes. The amplifier circuit uses only 7 dB of negative feedback, and the output has 5-way posts rated at 4 and 8 ohms. Power output is said to be 45 watts per channel.

      On the preamp end there are are 5 line inouts marked Tuner, Video, CD, Phono and Aux, with a Tape Monitor selected by a toggle switch. Other toggles enable Record Out, Mute, and Power. The Volume control is operated by holding the knob to either left or right to activate a resistor ladder with 70 steps, these indicated by a circle of LEDS around the knob. The Source selector acts in a similar fashion, here switching internal relays for each input.

      On the rear panel all the expected inputs are found, all high- quality unbalanced RCA jacks, but in addition to the fixed level record out is a pair marked Sub Bass Out, which according to the manual “is full frequency in bandwidth and its level is controlled by by the CA50 volume control”, s Audio Research has cleverly offered the options of adding a subwoofer, and of using the CA50 as a preamp, not to forget the multi-room possibilities as well.

      Shipped with its tubes carefully coddled in bubble wrap, the CA50 needs some tube biasing before operation, this hopefully done by the dealer, as it was in our case by American Sound of Richmond Hill. Whe it is turned on thereafter, the LED above the power toggle switch will flash for 60 seconds as it warms up in Mute mode. After all this was done, we had a listen to the CA50 through our Energy Veritas v1.8 speakers using tri-wire Wireworld Orbit speaker cable connected to the 4-ohm amplifier taps. The first source was the Dynaco CDV Pro CD player (Wtr 98), with its tube output stage. Since the CA50 also has a phono input (about which zilch is said in the manual: MM of MC, who knows? We had to find out), I also hooked our turntable up to it after determing the amp’s basic sound character with a selection of CDs, including, of course, our own high resolution recordings.

      Let’s get the Phono input out of the way first: though so named, it is, in fact, a line level input meant to be used with Audio Research’s (or anybody elese’s) outboard phono stage. I fed it with the output from our McIntosh MCP-1 MC amplifier to determine this, the result a very faint sound from the speakers.

      How can I characterize the sound of the CA50? Well, it’s both sonically and physically a little warm, but with excellent detail and delicacy. It doesn’t have the rather coarse overtone structure of many single-ended designs that passes for detail for some listeners, offering instead a real perception of nuance. Bass is well controlled and full, some of that determined by the Dynaco, as readers of that review will already know. It was just a little soft compared to our 3B ST, but definitely had impact and went very deep.

      Overall, the sound of the CA50 was impressively neutral and revealing, as befits a true high end component. It paired well with the CDV Pro to provide a very un-CD-like sound that did not tend to lose detail or ambient information. It’s a component for music lovers who value simplicity. There’s no remote control and no gadgets. The large, beautifully finished case, with its brushed aluminum fascia and black rack handles has an understated elegance that is all Audio Research.

Andrew Marshall