Classic Sixty Vacuum-Tube Amplifier
Tasked with developing the most cost effective amplifier that we could build, consistent with our standards of quality of construction and performance, the conrad-johnson design team turned to our flagship product for inspiration.
Borrowing heavily on the technology of its big brother, the ART amplifier, the Classic Sixty preserves the distinctive tonal character of individual instruments and voices, with each clearly located within the overall acoustical environment of the original recording. Musical transients are reproduced with realistic impact, but without artificial enhancement. Like its more costly siblings, the Classic Sixty captures the emotional impact of the live event, never getting between the listener and the musical performance.
There really is no mystery to the basis for outstanding musical performance: best results come from simple circuits executed with quality parts.
The Classic Sixty amplifier circuit design is about as simple as possible, employing just seven vacuum-tubes. Single-ended triode voltage gain and inverter stages are coupled to an output stage comprised of a single pair of ultra-linear operated EL34 tubes for each channel. As it is critically important that the DC voltage supplied to the gain stages be absolutely rock-solid stable, these voltages are provided by simple but highly effective discrete voltage regulators. And speaking of simple, maintenance of the Classic Sixty could hardly be easier: the owner need only make a simple bias adjustment using the built in bias indicators when installing fresh output tubes.
The use of premium quality component parts is the other half of our underlying design mandate.
In this area as well, the Classic Sixty is a leader in its class. Precision, metal-film resistors yield low noise performance for greatest clarity. Polypropylene and polystyrene capacitors, chosen to achieve a high degree of temporal accuracy, are specified for both the audio circuits and the regulated plate voltage supplies for the input and inverter stages. The result is an exceptional range of dynamics – reproducing both subtle variations in level as well as dramatic loud crescendos. Our proprietary trans-spectral wide-bandwidth output transformers contribute importantly to the extended, “airy” highs that help distinguish the Classic Sixty from ordinary tubed amplifiers.
The Classic Sixty offers an ideal introduction to the joys of modern tube amplifiers, while the ease of use, low maintenance costs, and reliability will be a revelation for those who have only experienced “entry-level” tube gear.
Those who wish to take the experience a step further will want to investigate the upgraded Classic Sixty SE, which upgrades the output tubes to KT120s and incorporates CJD Teflon Capacitors and ultra high-performance metal foil resistors in strategic applications in the circuit. Either model is sure to rekindle your passion for enjoying great music in your home.
60 watts per channel from 30 Hz to 15 KHz at no more than 1.5 % THD, both channels driven into 4 ohms (also available connected for 8 or 16 ohm loads)
0.7 V to rated power
Frequency Response (at 10 watts)
20 Hz to 20 kHz, +/- .3 dB
Hum and Noise
96 dB below rated power
1 x 6189, 2 x 6922, 4 x EL34 (Classic Sixty)
4 x KT120 (Classic Sixty SE)
13.25D x 17.375W x 6.625H inches