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Vintage threads from the first ten years

Overdriving delay input

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5/2/1999 3:07 PM
Blues Lyne	Overdriving delay input I have a '79 MXR Analog Delay and I seem to be overdriving the input when I use humbuckers or a Tube Screamer. It produces a bad sounding distortion. It sounds sweet if I back off the volume on the guitar or the out put from the TS. Is there a way modify the input to accept stonger signals without distorting? Thanks for your help, Blues

5/4/1999 6:14 AM

The big problem with analog delays is that there is not enough difference between the noise floor and the overload point. So most analog delays have a compressor/expander circuit built in (usually a NE570, NE571, or NE572).
You could always put a compressor /expander box to work here, there were some around in the 70s used with tape recorders as noise reduction systems.
Myself, I would use a resistor on the input and a couple of back to back paralled diodes from the cold end of the resistor to earth, the compression/distortion from this wont be near as bad as overdriving the BBD chip.

5/5/1999 1:15 AM
Blues Lyne	Paul, Thanks for your help. Blues

5/5/1999 8:41 AM

you're welcome.. this 'diodes as knee limiter' got me out of bad trouble, I had a design that 'locked up' on heavy guitar strokes.. an op amp was saturating on peaks, but I couldn't take the gain down without making the effect useless, and the production run boards were already done! Seems some guitars can put out 5v peaks, who woulda thunk it.. thrash rules..
I found LEDs made the best diodes for this (also i had a bucket of them ;-)

;-)

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