Moog Moogerfooger MF-104 Analog Delay

A delay circuit produces a replica of an audio signal a short time after the original signal is received. If you listen to the original and the delayed signal together, the delayed signal will sound like an echo of the original. If you then mix some of the delayed signal with the original signal and feed the mixture to the input of the delay circuit, the delayed output will be a string of echoes that die out gradually. You can determine how far apart the echoes are by adjusting the delay time of the delay circuit, and you can determine how fast the echoes die out by adjusting the amount of feedback from the delay circuit output to its input. In addition, you can determine how loud the echoes are by adjusting the mix between the original signal and the signal from the delay circuit output.

Today there are three types of delay devices: tape, analog and digital. The first delay devices used magnetic tape to create the delay. The sound was recorded on a moving tape and then played back after the tape had moved a few inches or so. Then, during the early 70s, large-scale semiconductor analog delay circuits became available. These were called bucket brigade delay chips, because they functioned by passing the audio waveform down a chain of several thousand circuit cells, analogous to water being passed by a bucket brigade to put out a fire. Each cell in the chip introduces a tiny time delay. The total time delay depends on the number of cells and on how fast the waveform is “clocked,” or moved from one cell to the next. Analog delays were less noisy, easier to use, and more reliable, and came to be more widely used than tape echo units.

More recently, digital delay units have come into use. In a digital delay unit, the sound signal is first converted to numbers. The numbers are stored in a digital memory for a certain time, and then retrieved and reconstructed into the delayed audio waveform. One significant difference is that the particular frequency and overload contours of well-designed analog delay devices generally provide smoother, more natural series of echoes than digital delay units. Another difference is that the echoes of a digital delay are static because they are the same sound repeated over and over, whereas a bucket brigade device itself imparts a warm, organically evolving timbre to the echoes.

The MF-104 Analog Delay is unique because it combines authentic, finely-tuned vintage analog bucket-brigade delay circuitry with total voltage control of all three performance parameters.