Waldorf Blofeld Keyboard - Manual (Page 49)

Sound Parameter
49 Blofeld User´s Manual
• Comb+ / Comb- Filter differ from the other filter
types greatly, because they don’t actually damp any
part of the signal, but instead add a delayed version
of the input signal to the output.
•
PPG LP Lowpass is a resonance lowpass filter with a
slope rate of 24dB per octave. Its characteristics
were modeled after the legendary PPG Wave
synthesizer and its integrated SSM 2044 chip. The
resonance of the SSM 2044 had a very special tonal
character, which has not been implemented in this
way in any other filter circuit or IC. If you have the
chance to directly compare the original with the
Blofeld, you will find the resonance (or Emphasis, as
it is called in the PPG) of both to be nearly identical.
w
What exactly is a Comb filter? A Comb filter is
basically a very short delay that can be controlled in
length and feedback. The delay time is so short that
you can’t hear its individual taps but a colorization of
the original signal created by peaks or holes in the
frequency spectrum. The frequency of the
colorization is set by the delay length, which is
controlled in the Blofeld through Cutoff, while the
amount of colorization is set by the Comb filter
feedback, which is controlled in the Blofeld through
Resonance
.
w
To learn more about the comb filters please refer to
the corresponding paragraph in the chapter „Sound
Synthesis Basics“.
Env Amount -64...+63
Determines the amount of influence the filter envelope
has on the cutoff frequency. For positive settings, the filter
cutoff frequency is increased by the modulation of the
envelope, for negative settings, the cutoff frequency is
decreased. Use this parameter to change the timbre of the
sound over time. Sounds with a hard attack usually have a
positive envelope amount that makes the start phase
bright and then closes the filter to get a darker sustain
phase. String sounds, on the other hand, usually use a
negative envelope amount that gives a slow and dark
attack before the cutoff rises in the sustain phase.
Since there are two filters, you could use the Filter
Envelope on one of them, and another envelope on the
second filter, buy setting this parameter for that filter to
zero and use the Modulation Matrix for the other used
envelope. Specially with the two filters placed serial this
can bring nice effects.