The conrad-johnson ART27A stereo power amplifier is a somewhat peculiar and non-standard product within the amplifier portfolio coming from the Virginia, US manufacturer. And it’s peculiar for several reasons. First and foremost, c-j amplifiers were always and are still very much traditional push-pull Class AB affairs which, if and when applied with creative wisdom and knowledge of audio electronics, yield respectable power output and a fundamentally good sound quality. Depending on the chosen output valve type and the number of pairs per channel, c-j designs regularly give from 60 up to 300 Watts per channel into any impedance. In short, they can drive almost anything with cones, domes or panels. Secondly, c-j power amplifiers have been renowned for a very conservative degree of hardship their output valves are ever submitted to; in other words, they run on a moderate bias current per valve thus vastly increasing the longevity and reliability of each one of them. This is more than just cost saving; conrad-johnson and its fan-base strongly hold to this being one of the secrets to excellent sound quality.
Paradoxically, alongside the launch of the ART300 mono and the ART150 stereo, conrad-johnson also launched another limited-edition power amplifier called the ART27A. The trio formed c-j’s 40th Anniversary line-up. Where the ART300 is a 300 Watt powerhouse, the other range-topper puts out just 36 Watts per channel in Class A from its quartet of KT88s operating in triode mode. Read that bit back to yourself if you are a c-j amp owner because it might take some time to settle into the ol’ noggin. I’m sure some might think this sends mixed messages, but I think it’s c-j addressing two sides of the 2019 tube amp market; the demands for more power and more grace, That being said, the ART300 is no slouch in the grace department in its own right, as we shall see later on.
Enter the ART27A. Externally, very similar to one of the ART300 monoblocks but for the missing cosmetics of the acrylic/metal encapsulation of all the valves. And that is where all the similarities end. Each channel delivers 36 Watts of pure Class A power through a carefully selected and matched pair of triode-coupled very special Gold Lion KT88 valves. The driver (input) section of the circuit consists of three Gold Lion ECC82 double triodes. One of them is shared between the channels at the very input, while the other two follow suit with their full individual capacity per one audio channel respectively. It goes without saying that very high quality Lundahl output and mains transformers have been used, as well as the usual plethora of conrad-johnson’s proprietary Teflon (PTFE) capacitors and Vishay resistors all over the power supply and audio circuits. The practical result of this, typical and established approach is a power amplifier of an extremely low level of circuit noise, excellent grounding and, also, a virtually non-existent amount of mechanical noises usually associated with transformers and chassis resonances. Amplifier output is coupled to speakers through those aforementioned premium wide-bandwidth output transformers optimised for Class A operation of triode connected KT88. A c-j tradition, pure copper speaker terminals and rhodium plated input RCA sockets come from Cardas Audio.