Korg SDD3000 Preamp Prototype

Analog preamp stolen directly out of a Korg SDD3000 rack-mounted digital delay - dubbed the Korgasm 3000.  Supposedly the "secret" ingredient in the tone of U2's guitarist The Edge.  

I kept the pre/post attenuators and inserted a buffered parallel effects loop in place of the SDD3000's digital delay circuit.  The effects loop has a send level control, phase switch, and a dry/wet blend control.  

After messing around with the circuit a bit I decided to add an extra gain stage in the effects loop and dial it in so the loop would be at unity gain with the send level control at 12:00.  This way the effects loop footswitch can be used as another boost stage, if so desired.  Had to take it apart a few times for this though so the guts are a little messy.

The preamp colors the tone and adds a hint of compression and sustain.  And with an internal charge pump that converts the 9VDC input to a bipolar 30V supply, this thing has PLENTY of output.

Designed and built at the behest of my buddy Ryan, who also picked out the color - just so everyone's clear on that . . .

Thinking about improving the design a bit and doing a small run of these if there's any interest.  

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