This amp can run without a preamp!
Simply plug your CD player directly into it. The 864SR has a 100K ohm constant impedance Alps input volume control, (that is improved quality over the #861), for just such a simple system! The CD player "sees" a constant high impedance load at all frequencies.
The Model 864 is the newest 2012 power amp. It has the same live, dynamic circuit with a few improvements that give an extended bass response that is fuller and richer. The bias is now even easier to set with the new selector switch. The tubes are now out in the open for real tube lovers and the new larger transformers are double shielded in attractive covers.
The 864 has zero feedback, and even better frequency response than the earlier models. The zero feedback design is much more challenging for the designer, but equally more enjoyable for the listener because of the increased dynamic range and excitement of live present-sounding vocals. The amp also has a built-in user adjustable contour circuit with three settings for use with other brands of speakers or listener preferences of circuit damping. When the contour switch is in the "Off" position there is no circuit and even the switch is out of the circuit.
The tube filaments are run on AC voltage which is lifted from ground by 40 volts DC, and wired with shielded twisted pair wires for maximum current handling, minimum noise, and a smooth voltage rail. Switches and contacts are either gold or silver. Tube biasing is user adjustable with factory supplied tool and Vishay trimmers, all easily accessed from the rear of the chassis. The bias procedure for the 864 is even easier than the earlier Model 860.
The amp is easily switchable from pentode to triode with an 18 amp solid silver contact toggle switch located between the KT88's. The amp develops a minimum of 60 watts in pentode and 30 watts in triode. If the user has efficient speakers, the triode mode offers some excellent dynamic sound. The RCA inputs and speaker outputs are hard gold plate over silver over copper for the best in long-life wear and maximum transfer of a clean unaltered signal.