Adding modulation to an anolog delay?

[ppatchmods]

Is it as simple as with a digital delay? do i need to change the value of the delay time pot? thanks in advance!

[Mark Hammer]

One of the best places to start would be to look at the schematic for the Boss BF-2 Flanger.  The BF-2 uses two control-voltage sources to drive the clock generator for the BBD.  One is the LFO, and the other is a stable DC voltage.  The two are blended together by the Depth control, such that the Manual control (equivalent to time/rate control in a delay) and LFO, in combination, never attempt to introduce greater voltages than is appropriate.

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I've added a modulation control to a delay by building an LFO driving an LED and then placing an LDR across legs 1 & 3 of the delay time pot. The LED and LDR are sealed up together light tight.

There is a depth control between the LFO and the LED it is driving. When the depth is down, the LED is not lit, and the LDR has resistance high enough that the current flows through the normal delay pot. When the LFO depth is turned up, the LED modulates and the resistance on the LDR drops low enough to modulate the delay.

By adjusting both delay time and LFO depth, it gets a wide range of sounds pretty much like you would expect - from crazy pitch sweeps to chorus, flange, and subtle vibrato.

[ppatchmods]

i have added modulation to the rebote but never to an analog delay. i was just wondering if it were the same type process(i think it is).

Mark, i'm gonna take a peek at the schematic. i had one of those pedals in my shop recently and IIRC it had some issues with swooshing noise when at rest...a whole nother issue. thanks