Tiptop BD909 Bass Drum - Manual (Page 2)

Introduction.
2
The BD909 is a recreation of Roland's TR-909 analog bass drum sound generator
adapted for modular synthesizer use. The front panel contains all of the controls
found on the original TR-909 drum machine, allowing you full control over the
sound’s volume levels to mix with other drums and accent levels, decay tune and
the envelope attack and decay segments. In addition to those original controls we
have also added new controls, further enhancing this legendary sound generator.
Let’s get started.
To start using the BD909, just plug a gate signal into the GATE input, plug the BD
OUT to your sound system, set the LEVEL half way, set the Overload knob to min,
set the ACCENT to halfway.
Tuning explained.
The BD909 contain three tuning control knobs plus a VC tune with attenuator knob
for scaling the control signal. This wide range of tune shaping enhances the original
circuit, turning it into a real analog bass drum laboratory. The OSC TUNE knob is
there to let you offset the starting and ending frequency of the bass drum sound.
The Tune Decay is the original tune knob found in the 909 machine but with a
slightly extended range. The Tune Attack is a new control which not only adds
variation to the sound, it also affects the Tune Decay knob, therefore creating
many more sweet spots than found on the original. The combination of these three
knobs are the main synthesis tools of the BD909.
Overload explained.
The BD909 is based on a triangle VCO and a sine wave shaper that filters the
triangle harmonics and producing a wave which sounds more like a sine wave.
The overload knob and CV input form a control circuit that was added to the
waveshaper, letting you overload the waveshaper circuit, therefore adding more
odd harmonics to the wave shape. In low doses this means more punch, and
as you keep overloading, the sounds get distorted up to total destruction.