Pitch vibrato

How to create true pitch vibrato

So you'd like to get those sweet vintage Boss VB-2 Vibrato tones out of your squeaky clean new Axe-Fx...here's how.

True pitch vibrato is created by modulating the time on a 100% wet delay line. Think about it. Have you ever twisted the delay time knob on an analog delay to get those cool alien spaceship sounds? Same concept only the knob twisting is done via an LFO and there is no dry sound to water down the effect.

Perusing the Axe-Fx's available effect blocks, the chorus is the best fit for this task. Compared to the delay block, the chorus block allows smaller increments of time delay and doesn't have a feedback (regeneration) path which we don't need anyway.

Checking the Chorus block's basic parameters, we have VOICES which is how many voices our vibrato will have. If you want to nail the VB-2 you'll only need one voice. The minimum choice is 2, but we don't really have to vary but one of the voices. RATE is the rate of the LFO and is directly analogous to the rate control on the VB-2. DEPTH is how much the delay time varies.

According to Cliff, the LFO varies the delay time "bipolar" meaning that it adds and subtracts delay time from the nominal delay time which is set in the advanced parameter menu. MIX should be set 100% wet to vary the pitch of the original signal with no original signal present. TEMPO you can use if you want to lock the rate to a songs tempo.

Spillover

The delay spillover settings prevents the clearing of the delay lines when switching presets. If you think of the Axe-Fx as a virtual collection of effects it's as though you simply took your delay pedal and instantly moved it around in the chain and changed it's parameters. If you're going to a preset that doesn't have the delay block then there will be no spillover.

You can have spillover by simply putting the delay block in the new patch. If you don't want delay in the new patch then set the input gain to the delay block to zero. If you do this you'll get spillover but no new delay. If you come from a patch with no delay block to one with delay, you'll get no spillover as delays lines are cleared if they are not used in a preset.

If you want delay to spillover from the last patch, but you want a different delay in the current patch, use two delay blocks in your new patch. The first should match the parameters of the other patch, except that the input will be muted. This will act as the spillover patch, as long as the number of the delay block 1/2 matches the last patch. Now you can add a second delay block of whatever type you desire for the new patch and use it normally.