Great River PWM-501 500 Series compressor/limiter

The compression range and palette of sounds that can be found with the 501 is virtually infinite. With its Feed-Forward and Feed-Back Control, you have two completely different sounding compressors. If you need aggressive transient shaping for drums and percussion instruments, just dial in your desired amount of compression with Feed-Forward mode. Or use Feedback mode for a seriously round and warm response on things like drum overheads, bass and vocals. You can dial in the perfect amount of glue for anything you want. It is a sweetly enhancing sound, that is well suited for all-duty workhorse compression.

Features:

• Output level control: This control sets the amount of make-up gain in the output amplifier. Use it to adjust the output signal level.
• Threshold control: This control determines the portion of the signal that the rest of the sidechain will use to control the operation of the PWM-501.
• Ratio control: This control sets the percentage of the control signal sent to the PWM attenuator. Fully counterclockwise divides the signal the most, giving the lowest ratio. The actual ratio is approximate, as it is dependent on the variables of the threshold, attack, and release times, as well as the setting of the feed-forward/feedback control.
• Attack time control: This control sets the initial charging speed of the time-constant capacitor. The circuit feeding this capacitor is an absolute value peak detector, so it can be very fast. It can also generate unpleasant distortion if it is too fast for the signal content. Faster attack times are in the counterclockwise direction of the control.
• Link switch: This switch will link the control voltage between PWM-501 units installed in a rack with the correct interconnections on the backplane bus.
• Release time control: This control sets the discharge speed of the time-constant capacitor. Faster release times are in the counterclockwise direction of the control.
• Bypass switch: This is a hard-wired bypass of the entire PWM-501 when depressed. The unit is also in bypass mode when the rack is unpowered.
• High-pass frequency control: This is a second order (12dB/octave) variable high pass filter that is inserted in the sidechain immediately after the feed-forward/feedback blend circuit. When engaged it can filter out bass signals that might otherwise influence the action of the PWM-501.
• High-pass engage switch: The high pass filter circuit is engaged when this button is pressed.
• Feed-forward/feedback blend control: This control determines the source(s) and the blend of the sidechain signal. In the fully counterclockwise position the source of the sidechain signal is entirely the input audio, in the clockwise position the source is entirely the output signal.
• Meter function, switch, and display LEDs: This switch determines the signal to the peak reading meter circuit. In the GR mode, the meter indicates 1dB of gain reduction for every LED lit. It indicates in a downward direction. In either the In or Out mode, the meter indicates the signal level at the respective signal point. All green LED’s lit indicates a signal level of +4dBu at the XLR.