I need some technical help here. I am currently in a discussion with a plugin designer about how I think it is impossible to accurately emulate analog delays digitally in either hardware or software. I have tried literally dozens of digital delays both hard and soft and none have been able to emulate that self-modulating ufo sound analog units such as Electroharmonix Memory Man, Ibanez DE-7 and AD-9 and Boss DM-2 (just to name a few) can do. Even the units that claim to truly emulate analog circuits fail on this aspect.

I know a lot of you here know what I am talking about. That unmistakable sound when you crank up the feedback, play a note, move the time knob back and forth and BLAM! Instant Butthole Surfers. My problem is, no one seems to understand what I am talking about. They say "try this plugin, it sounds analog" but I am not talking about the sound. I am talking about the behavior or the characteristics of the feedback circuit. I am not very technical in electronics so what is the technical explanation of what I am talking about? Is "self-modulation" an accurate description of what is going on here or is that the wrong term?

It may have to do with undesirable noise / capacitance (from a design perspective) in the feedback loop. A simple delay plug in will probably not feature this. (except for progressively amplifying the digtal deviation from the original analog signal at 100% feedback). Many digital delays have a lo-pass feature so that the stuff getting fed back sounds progressively more "dull", probably in an effort to mimic a tape delay.

Another difference-
I think I read somewhere on here that analog delays are typically capable of having a shorter time delay than hardware digital delays (1ms). Most plugins go to 1 sample or 22.7us. (at 44.1khz)

I'm not sure about this, but the term might be "self oscillating". At high feedback the system becomes unstable.. I've never heard "self modulating" used to describe a delay...

you can get that same effect - The "butthole surfers" effect - on an echoplex, i've done it.


but to answer your question, i know what you're talking about and I've yet to find a way to do it on any kind of "plug-in" usually i just suck it up and plug a stomp-box into the computer

the guitarport delays kind of self oscillate... it's as though they would, but line 6 made 100% feedback actually slightly less - so the signal dies away eventually. but when you turn the rate knob, you still get a certain analog-ish sound. reminded me a little bit of a dm-2, but not as extreme.

Isn't the Ibanez DE-7 fully digital, but with an 'analog sound' feature?
You can do the self-oscillation trick with many delays, the tape devices do it most wonderfully, though not as gritty as a pedal can. However the Boss DD-2 (a very good sounding no frills digital delay btw) has similar feedback effekt when cetrain knobs are maxed. I'm not sure this only happens with analog.

Well color me stupid! You are right! That unit is digital. Hell I don't own one, my friend has one and I just assumed it was analog by the way it responds. Thanks for bringing my attention to that, I stand corrected. Another digital delay pedal that sounds really good is the Guyatone MD3.

However, I was mainly talking about delay plugins which until today I never thought were ever able to emulate the response of analog delays. On that note I stand corrected as well. Gretz, this may interest you as well: Check out Voxengo's Tempo Delay at www.voxengo.com/product/tempodelay/
The programmer told me I should turn the feedback all the way up, set the filter type to LP (low pass) and that that would give the desired effect. He was right.

Thanks for your response guys. And Jason Smith you were right as well. I guess the term actually is self-oscillating.