Conrad-Johnson

It is quite a coincidence that two of our audiophile suppliers decided to come out with tube/solid state hybrid amplifier products almost simultaneously. (For a discussion of the other offerings, please see the Audio Research section of this newsletter.)

Conrad Johnson has released two hybrid products, one for stereo and one for multi-channel or home theater use. The Conrad Johnson Enhanced Triode Amplifiers are power amplifiers designed to capture the best attributes of both fine vacuum-tube designs and of the best solid-state designs. The ET250S ($7500) is a 250 watt per channel stereo power amplifier, the MET150 ($8500) a five-channel amplifier rated at 150 watts per channel. These sophisticated, zero-feedback amplifiers offer the refinement of a vacuum-tube amplifier with the guts and control of a solid-state amplifier.

Feedback is a common technique used to reduce measured distortion, but it can also have deleterious effects on a circuit's transient response. That's why many high end companies such as Conrad Johnson attempt to limit feedback as much as possible. However, eliminating negative feedback requires much more care in the design of the circuits, both in choosing devices and in power-supply design, and places greater demands on the parts. This, of course, makes the products more costly. That's why zero-feedback designs are usually seen only in high end products.

The ET power amplifiers use 6922 tubes for the critical voltage gain stage. The voltage gain stage of an amplifier dominates its sonic characteristics, and the ET amplifiers, therefore, exhibit the smooth, lucid midrange for which tube amplifiers are so highly esteemed. High-current bi-polar devices have been used for the output stages of these amplifiers, because of their extremely low output impedance and their ability to handle a great deal of current. This yields the fast, weighty bass and seemingly-limitless power reserve that are notable in these amplifiers.

Rock solid power supplies are needed to enable the audio circuits to reach their potential on musical transients. The ET amplifiers feature oversized main power transformers (so that the circuits are not starved for current), and massive power storage reservoirs with high-speed capacitor shunts to deliver quick, even startling transient response. Carefully designed DC voltage regulators isolate the critical voltage gain stages to prevent demands of the output stage from modulating and corrupting the input signal.

Finally, all of this careful design is implemented with the exquisitely-high-quality parts for which Conrad Johnson is internationally renowned. This means that, whether you're doing a stereo, multi-channel audio, or home theater system, you'll get a sound that is true to the long-standing Conrad Johnson tradition.