10
Front Panel Controls
On-Off Button
Push once to turn on the JC 3. There will be a slight delay as the circuits stabilize and the DC
servos settle down. When the JC 3 is turned on the blue glow around the On-Off button will
be brighter and the red P badge will glow brighter. Push again to turn off the JC 3.
Mono Button
Press the Mono button one time to parallel the stereo channels to mono. Press a second
time to return to stereo. Older mono records and stereo records with high levels of rumble will
sound cleaner when you select mono on the JC 3. The Mono button will glow blue when
stereo is selected and amber when mono is selected.
Design Overview
John Curl’s phono preamps are legendary. His approach to amplifying extremely low level
signals gives the listener the best chance to experience the full emotional content of the
source. In the JC 3 the physical implementation of the circuits closely follows the actual
circuit topology and the layout is as compact as possible to minimize pickup of external noise.
The preservation of low level signals is achieved by separating the critical audio signals from
the non-audio circuits and non-audio wiring. Each channel has its own circuit board and each
channel is fully enclosed in its own extruded aluminum “vault.” This vault shields the
sensitive circuits from the JC 3’s power supply and from external sources of noise.
The power transformer is an R-core type, which shares the advantages of a toroid
transformer for minimizing radiated hum. However, it is far superior to a toroid transformer in
preventing noise carried on the AC power line from passing through to its secondary
windings and into the power supply.
A second level of shielding separates the phono vaults from the power supply, power
transformer and even the transformer wires running to the AC inlet on the rear panel. This
shielding consists of two partitions of 3/8” low carbon “mild” steel to prevent any
electromagnetic radiation from reaching the phono modules. The rear panel of the JC 3 is
made of aluminum to prevent any electromagnetic interaction with the sensitive phono
circuitry.
Finally, the JC 3 has an on-board AC line conditioner to filter out high frequency noise and
distortion that may be present on your AC power line. This eliminates a potential source of
noise before it ever reaches the JC 3 power transformer. The resulting extremely low noise
levels enable musical nuances to emerge from an utterly silent background.