10.6

90Logic Pro Instruments
Comb PM uses bipolar feedback on the delay lines. The resonance control is bipolar,
allowing you to freely shift from negative (hollow sound) on the left to positive (bright and
peaky) on the right. This comb is useful for classic bright Karplus-Strong style sounds,
where the exciter impulse is not easily heard and the comb is more prominent. Take care
with your resonance level because it is capable of quickly going to extremes, which can
lead to feedback. Start with a resonance level of zero and increase (or decrease) slowly to
find a suitable effect strength.
For instrument modeling, it is best to assign combs as source filters, rather than in the
master filter or effect sections. Although comb filters can be used in the master filter
section, it is better to use the main filters for additional processing. Comb filters are also
available in the effects section but are not polyphonic, so you will achieve better results if
they are placed earlier in the signal path.
• Cutoff: Controls the delay time in the comb circuit. Lower cutoff values equate to a
longer delay.
• F-Back: Controls the amount of feedback in the comb circuit.
• Damp: Softens the frequency peaks in the comb-filtered spectrum.
Note: Sending a percussive sound into a highly resonant comb filter causes it to ring at
a frequency determined by the delay time you have set with the Cutoff knob.
Alchemy filter types: ring modulation
Ring modulation is a process in which a modulator and a carrier signal are multiplied. Each
frequency component of the modulator interacts with each frequency component of the
carrier to produce two sidebands: a sum and a difference (carrier – modulator). When a
filter is set to the RingMod type, the signal entering the filter acts as the modulator, while
the carrier is supplied internally by the filter.
• Frequency: Controls the carrier frequency.
• Mix: Applies a constant offset to the carrier.
• At 0%, the carrier wave varies between –1 and +1, resulting in classic ring
modulation.
• At 100%, the carrier wave varies between 0 and 1, resulting in classic amplitude
modulation. In this case, the carrier signal itself is present alongside the sum and
difference sidebands.
• Weird: Controls the carrier waveform.
• Set to 0% for a pure sine wave carrier. Use this setting to produce characteristic
bell-like timbres.
• Set above 0% to progressively truncate the carrier waveform. Higher settings
produce additional sidebands, typically resulting in noisy timbres.
Alchemy filter types: distortion
Alchemy filters offer several distortion effects.
• Bitcrusher is a harsher-sounding digital effect.
• Downsample is a lo-fi digital effect (similar to Bitcrusher but is frequency dependent).
• Mech is a more metallic-sounding distortion.
• Tube is a classic tube distortion effect.