(FROM MANUAL)
■ Introduction.
The BD808 is the Roland TR-808’s Bass Drum circuit adapted for use in Eurorack format and tuned to sound like a machine that come fresh off the original 80’s assembly line. The adaption to modular format has allowed us to add some special features like independent Accent level, a high-powered gain stage, dual input pulse-shaper and extended decay; all without compromising the signature sound of the TR-808.
■About the Making of the BD808.
A widely used technique with TR-808 machines is to run the drum sounds through outboard amplifiers to add gain and then pass the sound through just about anything to generate additional harmonics caused by clipping a distortion. In the BD808, we have already included this high-powered output gain stage capable of producing signals up to 20Vpp, extending from the original palette of sounds and allowing you to get an assorted array of harmonized bass drums ranging from sharp attacks to crushed tones using this simple yet effective technique. On the inputs, we have also designed a dual pulse-shaper circuit so you can trigger your BD808 with trigger/gate signals from step sequencers, clock dividers or any other pulse/clock sources. This saves you the need to shape the pulses sent to the module and ensuring the same stable sound at its peak power, regardless of differences in your pulse source.
■Dynamics and Gain.
The BD808 offers an enhanced output gain stage over the original 808 design. This
addition allows the output signals to get very hot so that anything flowing from the
module will be overdriven, generating additional harmonics through distortion and
clipping of the sound. In fact, the BD808 can go even hotter than standard levels of
modular VCO's. This capability is one of the most useful ways to get beefier and grittier
sounds out of this circuit. Obviously we didn't invent the idea, it had been done for years
by stringing 808's through multiple gain stages and tubes to overdrive the levels and
create distortion. However, this idea has never been implemented as part of the sound
generator itself to provide hot gain levels right from the source. This effect is easily
noticeable by sending the audio output into line level instruments such as computer
audio interfaces, outboard multi-effects, mixers, and even low level devices like guitar
pedals, mic preamps etc. This enhanced gain stage will also make any synthesizer
module operate at peak levels while adding interesting harmonics or digital artifacts in
the case of digital processing modules.
To get the BD808 to its hottest levels, set the LEVEL to max, set ACCENT to max, and
set DECAY to mid-way. At these settings, the BD808 can output a signal up to 20Vp.p
(Most professional computer interfaces usually start clipping at 10Vp.p!!) Now you have
an additional 10 volts to get varying sounds from sharp attacks at the start of the clipping
to crushed tones at the end.
On the other hand, if all you want is a nice, clean and punchy 808 sound, setting the
range of the LEVEL knob somewhere between 0 to 50% will cover tha
■Dynamic Accent and Level control of any drum sound in the mix is a big part of making
a beat sound right. Dynamic Accent provides emphasis on a particular note through
loudness. In analog circuits like the BD808, the accent pulse physically "hits" the
resonating circuit harder and provides not only a louder sound but also slightly more
attack (much like if you were to hit a real drum harder or softer with a drum stick.)
While the original 808 has one global accent knob affecting all of its sounds
simultaneously, the BD808 (and all other drum modules in this series) others an
independent accent level control. This feature adds far more dynamics than what was
possible with the original machine.
■Decay explained:
One of the signature parameter of the 808 is its decay and in the BD808, we extended
the decay time to the maximum amount possible by this circuit, right before
self-oscillating occurs. If you hear your BD808 producing a low tone even without
having been triggered then the DECAY knob is set the maximum and the BD808 is
slightly oscillating. Turning the knob slightly back will eliminate the oscillation. Please
note: Not all BD808's will self-oscillate, this is a matter of the tolerance in its circuit.
■Tone explained:
The TONE knob controls the cutoff frequency of a low-pass filter that the drum sound
goes through. The higher the knob setting, the more high-frequency harmonics are
passed, resulting in the classic 808 Techno "basketball" sound with a tight, strong
attack. The lower the knob is set, less high-pitched harmonics are passed through,
resulting in a softer attack and a darker, smoother sound: a classic Marvin Gaye
'Sexual Healing' type of sound.