Getting to know the lfo – Moog Music MF-104M Analog Delay User Manual

Page 6

FIGURE 7

FIGURE 8

SHORT

LONG

DELAY TIME = .2

DELAY TIME = .6

FIGURE 9

Take a little time to experiment with various settings of the

DELAY TIME,

SHORT/LONG switch, and FEEDBACK.

Here are some things you will notice:
•Changing the

SHORT/LONG switch position either halves or doubles the

DELAY TIME and thus compresses or stretches the delayed signal currently
in the Delay Line by a factor of two. This results in the pitch of the delayed
signal being shifted up or down an octave.

•The

FEEDBACK control creates the series of echoes by mixing a portion of

the delayed signal back into the Delay Line. With the control set to about
8, the echoes sustain indefinitely. With the

FEEDBACK control set above 8,

the echoes build up chaotically into some amazing electronic textures that
can be both edgy and blurry at the same time.

GETTING TO KNOW THE LFO

This section demonstrates how the LFO
modulates the Delay Line.

Adjust all Delay controls as shown in

Figure

10. Press the BYPASS control to bypass the
effect (

BYPASS LED = Red).

Play your instrument for a few seconds. Tap
the

BYPASS switch again to turn the effect

back on and play some more. Hear the dif-
ference? This is due to the fact that with the
effect on the Delay Line is still in the circuit
and is creating a very short (40 millisecond)
echo of the signal.

FIGURE 10

SHORT

LONG

.05

Adjust the

FEEDBACK as shown in Figure 7, and tap the

BYPASS switch to turn the effect OFF. Then press and hold
the

BYPASS switch until the LED turns orange. The MF-104M

is now in

SPILLOVER mode.

Play your instrument to build up some echoes in the Delay
Line. Now tap the

BYPASS switch to turn the effect off while

continuing to play. The signal from your instrument will not
be sent through the effect but any audio currently in the
circuit will continue to sound as if the effect were on. Pressing
and holding the

BYPASS button for two seconds toggles

your Analog Delay between modes.

•In

NORMAL mode, turning the effect OFF shuts off audio

from the Delay Line. Any new signals bypass the effect.

•In

SPILLOVER mode, turning the effect OFF allows audio

currently in the Delay Line to continue while any new signals
bypass the effect.

Play your instrument while turning the

TIME control as in

Figure 8. You’ll hear the pitch of the delayed signal change
briefly and then return to pitch.

As you change the

DELAY TIME the signal becomes

stretched or compressed as it goes through the delay circuit,
thereby speeding up or slowing down the vibrations.

When you change the

DELAY TIME you are changing the

clock rate of an oscillator that determines how fast signals
go through the individual circuits in the Bucket Brigade
Device (see

Figure 9).

Adjust your LFO controls as shown in

Figure 11. Play your

instrument and you’ll hear a classic chorus effect. How
does this happen?

We just noted that changing the

DELAY TIME changes how

fast signals go through BBD in the Delay Line. And, you’ll
remember that changing the

TIME will cause pitch shifting

of audio already in the Delay Line due to time compression
and expansion of the signal.

In the MF-104M the LFO is used to modify (or modulate) the
rate at which signals go through the BBD based on the chosen
WAVEFORM, RATE, and AMOUNT. In this example of a
chorus effect, the LFO is smoothly modulating the

TIME with

a slowly changing sine wave of low amplitude (small peaks
and troughs). Because the sine wave is “gentle”, only minor
pitch shifting occurs.

FIGURE 11