via this auction
There are three main knobs to adjust delay time, feedback and wet/dry mix. Each of these parameters can be externally controlled by control voltage or expression pedal. Additional knobs to adjust the Drive or gain of the audio input to the delay, Loop Gain which sets the gain of the external feedback loop, and the Output Level knob are also available. So why is it a limited edition? Big Briar has secured a supply of the last analog delay chips and so only about 1,000 units were produced. The final units were sold in 2001 and the MF104 Analog Delay remains one of the most sought-after of the moogerfoogers."