Analog Delay Modulations

[mrscientificterms]

So I posted a thread up here recently about Cool Audio BBD chips.  They are great.  I breadboarded basically a Boss DM-3 clone with them, it sounds nuts good.  I am enjoying tinkering with it.  I'm  curious how/where some of the builders (EH, for example) are getting the modulation effects from these chips.  Thanks a bunch!

[WhenBoredomPeaks]

An LFO signal is constantly "adjusting" the delay time of the chips if i am right. If you change the delay time knob while playing you can hear that the pitch of the repeats is changing.
That is the modulation which happens there, for example chourus effect is the uneffected signal blended with a vibrato (changes in pitch) effected signal.
Anyways the much wiser guys gonna appear soon, they can probably explain it better.

[Top Top]

I recently made a delay/chorus/flange out of a karaoke boombox that had an echo built in. I built a simple dual opamp LFO ->led->ldr (if you search the forum for "uglyface LFO" you can find the circuit).

The LDR is bridged across the pins of the delay time adjustment, so that when the light to the LED fluctuates, the resistance across the pins dips, and modulates the delay time. On very short delay times with only a minimum of modulation, this makes a chorus type of sound. Faster speeds make a vibrato effect.

With a medium LFO speed and a little more depth, it can make a "crappy tape machine" effect (tape speeding up and slowing down). On longer delay times with more modulation and repeats/regen, it makes all kinds of wacky sounds.

Same concept is used in most flanger/chorus pedals I believe.