Design Overview
Based on the classic lines of the P600 Power Plant, this is built in true ‘battleship’ fashion. This 95 pound audio sculpture is simply magnificent in its build quality and attention to detail.
The side heat sinks are on hinges and fold down to expose the C250’s circuitry for easier access to the internal circuitry.
No expense has been spared on the most visible evidence of the Classic approach to power amplification. The look exudes finesse.
The front panel is a nearly two inch thick combination of extruded aluminum panels tied together both top and bottom with one inch slabs of hand finished aluminum. The entire assembly is then melded together to form the luscious curves you see.
Parts quality is second to none. Low ESR capacitors, each with film and foil bypass capacitors, 1% resistors throughout, 40 hand selected high current bipolar output devices, two custom wound and individu- ally serialized 800VA toroidal transform- ers, and the front panel meter is a custom manufactured replica of the classic Simp- son volt meters of years ago. Nothing has been spared in the Classic 250.
The design idea behind the Classic 250 is based on the marriage of four discrete and independent systems. The fact that each of these systems is completely indepen- dent both physically and electrically from the other is one of the keys to the Classic 250’s sonic success.
The four sections are:
•The input gain stage
•The internal Power Plant
•The output X1 stage
•The main power supply
The Input Gain Stage
This critical element is, in large part, re- sponsible for the way the amplifier sounds. By carefully tuning the audio parameters of the input gain stage we can tweak and play with the amplifier until it sounds abso- lutely musical.
In the Classic 250, the input gain stage consists of two gain blocks: a zero feed- back JFET input stage and a zero feed- back bipolar stage. Both of these stages are fully differential.
The input gain stage runs at extremely high voltages. In fact, the 200 volts used by this stage is one of the reasons why the C250 sounds so open and musical even during the loudest passage.
All the C250’s 30 dB of gain is produced by the input gain stage. This stage is com- pletely independent from the output cur- rent gain stage. The input stage is fed by its own regulated power supply that gets its power from a built in Power Plant.
Because the input gain stage has no inter- action with the output stage, the Classic 250 sounds the same on virtually any loud- speaker load.
The Internal Power Plant
Our Power Plant AC regenerators have revolutionized power within people’s homes forever. Now it is available in a specially tuned version designed to en- hance the performance and long term reli- ability of the C250.
The 40 watt Power Plant inside the C250, with its own discrete and custom wound toroidal transformer, independently powers the entire input gain stage and was hand tuned to maximize the amp’s performance.
After hours of listening tests we finally settled on one of our original Power Plant favorites, 120 Hz sine wave. This provides the cleanest and most open sound for the
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