Tonepad CE-2 vibrato mod- kind of weird

[MikeH]

I did the vibrato mod to my tonepad CE-2, and instead of having a nice smooth warble, it has a very abrupt transition.  Almost like someone playing 2 adjacent notes on a piano.  In others words, instead of the pitch changing like a nice smooth sinish-type wave, it changes like a square wave.  Anything I can do to smooth it out?  The chorus sounds fine otherwise.

Edit:  For those unfamiliar with this mod, it consists of disconnecting one leg of r21, which removes the dry signal and leaves only the modulation.

[Mark Hammer]

I have that mod on mine and it does not behave the same way as near as I can remember.

[JasonG]

The key to getting it to sound like a vibrato is to keep the depth set low. I have 3 mods (speed/vib/"spacey sound ")on my ce-2 I can get the sound your talking about. I have a VB-2 ,the Ce-2 sounds good but not the same.

[MikeH]

Yeah, I guess with the depth set low it *feels* smoother, but it is still the same square-wave-type modulating.  So, what in this build is responsible for the "smoothness" of the modulation? 

[Mark Hammer]

Try this out.  Use a DPDT toggle for your vibrato.  In vibrato mode it lifts the connection for R21, but adds a second .033uf cap in parallel with C21.  That will add some lag or "blurring" to the LFO, though more at faster speeds, which is typically what you use for vibrato.  When you switch back to chorus mode, the R21 connection is restored, and the ground connection for the added cap is lifted.

The original Small Stone included a similar, or rather analogous lowpass filter after the LFO such that slower sweeps would take place as is but faster sweeps would have some of the "edge" of the LFO taken off.  I installed it on my Ropez and I like it very much.  Though the CE-2 LFO is driving a clock circuit, rather than phaser stages, you are still fundamentally dealing with the abruptness of the sweep.  So maybe this will work out.  Note that if C21 and R35 are either at the top or bottom of their respective tolerance ranges, you can probably expect audible differences in the "choppiness" of the LFO output.

[MikeH]

Cool.  Thanks Mark, I'll try it out.