PS Audio C250 - Manual (Page 3)

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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