Another project done – did a input buffer mod on a Danelectro Dan Echo DE-1. Now this things sounds awesome. If you don’t know the Dan Echo, it’s an inexpensive but very versatile digital delay pedal. It’s not boutique or a fancy high-end rack unit, but what it does, it does it well!This mod was documented by Jürgen Müller back in 2002.
The biggest issue is the low input impedance which creates a bit of loss in the low end when it’s in the signal path. The input buffer uses a transistor, which has been replaced by an opamp and changed a couple of resistor values to provide the correct impedance match. Essentially, you’re replacing the resistor R204 and R11 with metal film resistors valued at 2k2 ohms, removing R13, and also remove transistor at Q1. Replace the transistor Q1 with the opamp as detailed in the article, also one of the IC pins will go to ground on the now vacant R13. I used a piece of perfboard to mount an IC socket while I did my point to point connections, because that way I’m not applying heat directly to the IC. The resistors are 1/4 watt, 1% metal film from Build Your Own Clone, also the DIP8 socket. The TLV2461 full size DIP8 opamp I got from Digi-Key. Full details at the link below, including a schematic.
The pedal is not true bypass, but since it’s well-buffered now, it should play nice-nice with your signal. Now this pedal sounds terrific! If you’re interested in this mod, I got it from Jurgen’s website here