Stopping an LFO

[kristoipher612]

Hey everyone, i was wondering how to stop an LFO in a circuit so i can manually move the sweep of a modulation effect(i.e. the Electric Mistress)?  is it simple?hard? what all do i need to know.  thanks for any responses.
kris

[niftydog]

You couldn't really stop it and manually alter the level. But you could disconnect it and control the sweep manually (eg; with a foot pedal).

Got the schematic?

[ExpAnonColin]

You could basically stop it by putting a very very large value capacitor in series with it's timing capacitor, or even a series resistor with the timing resistor....  basically slowing it down so much that you don't notice it going.  Schem?

-Colin

[niftydog]

hey, there's an idea. Then you use an op amp to "mix" the "stopped" LFO and an external DC control level...  there's some unpredictability to that setup though. but a good idea is a good idea!

[ExpAnonColin]

I've done it, sans the external control, before as a mod.

-Colin

[jplaudio]

Hey everyone, i was wondering how to stop an LFO in a circuit so i can manually move the sweep of a modulation effect(i.e. the Electric Mistress)?  is it simple?hard? what all do i need to know.  thanks for any responses.
kris

Most commercial flangers have this capability with a manual control that sets a
fixed voltage going to the VCO along with a Range control that mixes the LFO output and the fixed voltage. Take a look at the EH EM schematic to see how the range control is switched from using the LFO output to a fixed voltage at the opamp driving the VCO, simple but effective.
Any effect that uses a VCO can be can be converted to a manual sweep by using a varible voltage in place of the LFO output voltage.

[R.G.]

Stopping an LFO is not hard.  I did that for an effect in the Vibra-Matic mod to the EAN Tremolo. See

http://geofex.com/FX_images/vibmatic.pdf

From March 2001.

However, as the others note, just stopping an LFO isn't what you're talking about.