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The RATIO control has 6 steps between 1.5:1 to 8:1 to achieve a range of
compression from subtle to extreme, and the THRESHOLD control has 31 detented
steps between -25dBU and +20dBU to handle a wide variety of input levels. MAKE
UP GAIN has 31 steps from -6dB to +20dB, and is affected by the blend setting
(more on this later). The HPF to SC button moves the Sweepable HPF in the mic
pre to the compressor side chain, reducing the impact of low frequencies on the
compressor’s response. The SC INSERT allows more elaborate equalization of the
side-chain signal, accessible via TS I/O on the rear panel.
The BLEND control is incredibly useful on the Diode bridge compressor, allowing
the user to gradually mix colored compressor sound with the dry signal — giving
the Shelford compressor a potential for subtlety and precision not found in its
predecessors.
Additionally, the Diode bridge compressor is optimized to allow for overdriving
the diode bridge itself with higher input levels. With signals above 20dBU, the
diode bridge becomes fully saturated, creating dynamic harmonic content. By
manipulating input levels and the blend control, the diode bridge circuit can be
used as an automatic tone shaping tool even with minimal gain reduction.
INPUT CONTROLS
DI and Thru Jacks
These 2 jacks are used for mic/direct injection (DI) or instrument/line inputs and
are simply paralleled and wired together. Inserting a plug into the input jack breaks
the normal rear-panel Mic input and allows the user to access the full range of Mic
Gain and Trim. These jacks have a 2.2 megohm input impedance that minimizes
source loading, thus improving top end response. This factor coupled with the
sheer amount of gain that is available makes these inputs extremely versatile. Note
that if Line is selected and illuminated (button in) using the Mic/DI/Line switch, this
will override the 1/4” Instrument Jacks.
MIC/DI/LINE
Switches between microphone/direct injection input (button out) or line input
(button in).
Gnd Lift
This switch separates the direct connection from audio signal ground to chassis earth.
Signal Present LED
This LED is dual function. When green, it indicates “Signal Presence” (a minimum
signal level of -20dBu). When red, it indicates 2-3dB below input stage clipping of
the Mic/Line stage (+23 dBu while the pre actually clips at +25 dBu).
