The Delay Control
The Oakley Flanger uses a high frequency voltage controlled oscillator (HFVCO) to clock the
BBD devices. The faster the clock the shorter the delay time. The clock runs from 33kHz to
just 1MHz. The clock can be controlled by the front panel delay control pot and control
voltages sent to the CV1 and CV2 sockets. Increasing positive voltages will decrease the
delay time.
The delay control pot will create the longest delays at its minimum setting and shortest delays
at its maximum setting. This may seem counter intuitive if you think about the module as a
simple delay line – most delay lines would have a delay control that would increase the delay
as it is turned up. However, the flanger creates its distinctive sound by a form of notch
filtering whereby some frequencies in the audio spectrum are cut and some are boosted.
Shortening the delay time gives the impression that the filtering effect is rising in tone. It's
actually more complex than that but having the delay pot work in a reverse fashion does seem
to sound more natural.
The delay time goes from approximately 500uS (0.5mS) to approximately 15mS. Control
voltages applied to either CV1 or CV2 will extend this slightly but the module has limiters in
place to prevent the module from going too far away from its intended range. With the delay
pot in its middle position the delay time is around 3mS.
For flanging effects you can use the full sweep of delay times from 0.5mS and 15mS. For
chorus and vibrato type one would normally use delay times of around 5mS to 15mS. All of
these effects require the use of some form of modulation. That is, the delay time is dynamically
altered to create movement in the sound. Modulation sources normally take the form of a
connected LFO with triangle or sine waveforms available. However, you can also use a
sequencer or envelope generator. With an LFO as the modulation source the delay pot is used
to set the mid point by which the modulation shifts the delay time. The effect heard varies
greatly with delay time, modulation depth, modulation waveform and modulation frequency.
Vibrato is best heard from the raw delay output and using a sine LFO of around 6Hz to gently
modulate the delay time. Chorus is best done with a relatively slow moving triangle wave and
using the mix output. The pitch shifting effect created by modulating the delay time is more
noticeable at longer delay times even with only small amounts of modulation.
Flanging requires the use of feedback while both chorus and vibrato effects are done with no
feedback. The greater the amount of feedback the more pronounced the flanging effect.
Feedback
There is a feedback input socket, a feedback pot and a feedback switch. For the switch and
input socket, feedback is abbreviated to FBK.
The FBK IN socket can be used as an additional input which will add to the signal going into
the INPUT socket. The Feedback control pot will then control the level of the FBK IN signal.
If there is no signal plugged into the INPUT socket and the input is being applied solely to the
6