Stereo Mode:

Channel One and Two crossover functions are identical.
the input signal passes from the xlr connector, through an RFI filter which removes spurious radio frequencies. A differential amplifier removes common mode noise. A 15 Hz, 4th order Butterworth high-pass filter prevents damage due to over-excursion of the cone in vented low-frequency enclosures. A front panel switch allows this filter to be bypassed if desired. The signal then passes through a variable gain stage with ± 12 dB of gain, set by the Input Level control. The clip LED monitors the signal level after this gain stage and lights 3dB below clipping.

The signal then enters the first 24dB/octave crossover stage. The crossover frequency is adjustable on the front panel and rear panel switches allow the low crossover frequencies of each channel to be divided by ten. The high frequency output of this block feeds a second crossover block which divides the Mid and High frequencies.

The Low and High frequency signals pass from the outputs of te crossover blocks to the individual mute circuits that are controlled with front panel switches, then to the output level controls with ±12 dB of gain. Rear panel switchs allow the polarity of the servo-balanced outputs to be selected before feeding the XLR output connectors.

The Low Frequency outputs of Channel One and Two crossover blocks may be summed together to supply a Mono Subwoofer output. This signal is available at Channel One's Low Frequency output only.

Mono Mode:
For Mono 3-way appliations, a switch on the rear panel replaces the normal input to Channel Two's crossover block with the high frequency output of Channel One's crossover block. channel Two's Low Frequency Output becomes the Mid-Frequency output.
Only the lowest frequency point may be divided by ten.
The LF sum switch should not be engaged in this mode.

Stereo and Mono Modes:
A rear panel, two terminal barrier strip allows the audio ground to be separated from chassis ground.
All outputs are electronically Servo-Balanced and use differential amplifiers for each phase, connected so that the output of each amplifier also applies 6dB of negative feedback to the input of the other. Then, if either leg of the output is shorted to ground by an unbalanced load,the feedback is removed from the opposite leg and its level increases by 6 dB thus maintaining constant level to the load.
The 4th order Linkwitz-Riley crossover block is a state variable filter with two desirable properties. First the outputs of the crossover sum to unity, which results in a flat frequency response with no peaks or dips around the crossover points. Second both outputs are in phase at every frequency. This allows the drivers to be time-offset corrected (time aligned ) at all frequencies rather than only at the crossover point.