Re: [Harp-L] Feedback and Analog Delay

[Richard Hunter <turtlehill@xxxxxxxxxxxxx>]

Excuse me if someone else already answered this...

Any delay adds signal to the original signal.  That's the nature of what a delay does: it takes the original signal, and adds one or more repeats at an interval specified by the delay controls.  Delay controls usually include rotary controls or sliders for number of repeats ("feedback"), delay time interval (which can usually be set to anything from a few milliseconds to 2 seconds or more, depending on the unit; anything less than 20 milliseconds won't be heard by the human ear as a discrete repeat), and decay (the extent to which successive repeats diminish in volume over time), plus a wet/dry control (which controls the relative loudness of delayed signal and original signal).

If a lot of repeats are specified (meaning the "feedback" control or equivalent is turned up high) with low decay (meaning each repeated signal is pretty close to the original in volume), then the overall signal can get to be a lot louder, because all those additional repeats are piling up.  If the original signal was close to feedback, then the delayed signals can push it over the line.  

In fact, if you turn the feedback control on most delays up all the way, you get feedback in a very little while whether or not the original signal was close to feeding back.

In most cases lots of repeats aren't necessary to achieve the desired musical result.  In fact, cascading repeats usually just clutter the overall sound of the band.  The exceptions are when you want something really spacey, where lots of repeats certainly get that message across, or where you want to use a tempo-synced delay to emphasize the rhythm of a piece--the latter technique is used on thousands of electronica and dance records, and is also a favorite of the Edge, U2's guitarist. 

You can also reduce the amount of signal gain added by the delay by adjusting the wet/dry control.  In most cases, it's more musical for the delayed signal to be at lower volume than the original, and to drop in volume from repeat to repeat--that mimics what happens in nature, where a delayed sound (say, from shouting "hello" in a canyon") is usually at lower volume than the original, an each successive "hello" is quieter still.

Regards, Richard Hunter 
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