A simple tweak to delay circuits/builds

[amptramp]

You might want to bring the feedback signal out to a jack that goes out and take the input from a jack that comes in.  You can have all kinds of fun with what you do to the feedback.  Distortion, frequency doubling, frequency halving, EQ and tremolo come to mind.  It may not sound like a true echo but it will be something unique.  When nothing is plugged into the jacks, there could be a shorting contact between them so connection is made without needing a separate switch, just like some amplifiers use.

[Paul Marossy]

The Ibanez EM-5 Echomachine has back to back 1N4148 diodes in the delay line.

I always thought that was noteworthy... 

That is interesting... but I think they are probably there as limiters. Any clipping of the signal is probably just a side effect of using simple devices like opamps, and is a "best compromise" with what they have to work with while trying to keep things as inexpensive as possible, not the design intent.

In any case, that Mitsubishi M65831AP digital delay chip is interesting. Never heard of that one until I looked at the EM5 schematic.

[Mark Hammer]

The Boss BF-2 Flanger also has a pair of back-to-back diodes in the feedback loop of the mixing stage feeding the BBD.  The purpose seems to be to act as a cheap limiter to constrain the combined feedback+input signal from driving the BBD too hard.