LFOs as Attenuators
 Offset Generator   LFOs as Attenuators

Using the LFOs as Attenuators and DC Offset Generators

Part 2: Using LFOs as Attenuators.

By Kirk Slinkard

Have you noticed that if you use something like the MODWHEEL as a modulator on an LFO, you have no control over the WHEEL's adjustment range? Does the vibrato level ever get way too much when the wheel is all the way forward, and you wish you could tame it a bit? There is a way to optimize this. 

LFO Domino Effect

Our demo patch for this is a basic piano that uses the MODWHEEL to detune one OSCILLATOR for that jangly out-of-tune sound. But if you use the WHEEL directly on the OSCILLATOR, you can only use a small part of the adjustment range or else it will get too far out of tune to be musically useful. For this demo patch, the MODWHEEL modulates LFO3, which then modulates LFO2, which in turn modulates LFO1. All the LFOs are set with L1=00, so they give out nothing until the MODWHEEL is used. This chaining effect reduces the total range of the MODWHEEL each time it goes through an LFO. Notice on the OSCILLATOR 3 page that the first modsource is set for LFO3 at a value of +1 (minimum nonzero value), but you may prefer to save it at LFO2 after comparing. Here is a chart showing what happens as you assign the WHEEL and different LFOs in this chain as it's modulator, try all 4 of these for yourself:

Chart 2

OSCILLATOR 3
WHEEL
LFO3
LFO2
LFO1

Modulator #1 =
Too much range - about 1/4 tone maximum.
A musically usable range.
Also musical, more subtle.
More like a slight chorus than an out-of-tune effect.

The Positive Side of Being Bipolar....yes, those *are* little SQ-80s!

You can see that each LFO stage in this chain attenuates the WHEEL's range. This can be used with other modulators, but be aware that this only works with the positive half of any “bipolar” modulators. So (for example) an envelope would have any negative values lost. Similarly, it also cuts off the bottom half of the LFO's other waveforms.

Remember, the SQUARE wave we're using here only has a positive component so it wouldn't be affected by this. In fact, I just tried LFO3 on both the SAWTOOTH and TRIANGLE waves for vibrato, and both had the bottom halves chopped off by this LFO chain for a very lopsided vibrato. Maybe something to consider if you ever should want that effect.

But if you do, don't ever talk to me again.

Patch Name: PIANO

OSC1  -1, 00, 00, PIANO, OFF, -, OFF, -
OSC2  1, 00, 00, SINE, OFF, -, OFF, -
OSC3  -1, 00, 01, PIANO, LFO3, +01, OFF, -

DCA1  59, ON, KBD2, -06, OFF, -
DCA2  40, ON, KBD2, -37, OFF, -
DCA3  56, ON, KBD2, -06, OFF, -

LFO1  00, ON, OFF, SQR, 00, 00, -, LFO2
LFO2  00, ON, OFF, SQR, 00, 00, -, LFO3
LFO3  00, ON, OFF, SQR, 00, 00, -, WHEEL

ENV1   (NOT USED)
ENV2   (NOT USED)
ENV3   +63, +55, +00, 44L, 22,  00, 12, 58, 12, 23

 

ENV4   +63, +49, +00, 42L, 00,  00, 22, 61, 12R, 23

FILT  023, 07, 08, ENV 3, +56, OFF, -

DCA4  08, 63, KBD2, +63

MODES ON, OF, OF, 00,  OF, OF, ON, OF

SPLIT/LAYER (NOT USED)


So even if you can't get into all this techno babble, here are a couple of free patches. And the Scoreforsale website can boast that it really is continuing where the Transoniq Hacker magazine left off.

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