The PTWobble, StompLFO Modulated Delay is a guitar pedal that uses the StompLFO to apply modulation to a PT2399 delay. The audio path begins with a standard op-amp buffer circuit, followed by input filtering around pins 16 and 15 of the PT2399. The signal then goes through the filter and into the delay within the PT2399. Post-delay filtering occurs around pins 13 and 14 before the signal returns to the outside world at C13. The signal then splits, with one path going to the Repeats pot and back to the input filter via R17, while the other path goes to the Wet/Dry output mixer, IC1.2.

The usual 50K “Delay Time” pot on pin 6 of the PT2399 is replaced with a vactrol and a 47K resistor. This allows for setting the maximum effective resistance of the LDR, in this case, limited to 47K. This is about as long a delay as you can get from the PT2399 before it becomes overly crunchy. The audio path is typical of a PT2399 circuit, with an added input buffer and a proper wet/dry mixer.

The StompLFO part of the circuit includes power input protection and filtering, and a virtual ground creating a Vbias level. It also features a 10K Delay pot connected to a TRS jack socket for an expression pedal, allowing for foot-controlled delay time adjustments. There’s also an optional Tap Tempo footswitch J8/Tap for setting the rate of the LFO, not the delay time. An optional Sync Input allows for synchronizing the LFO to incoming clock pulses from another device like a drum machine or sequencer. The schematic also includes connections for power for the Bypass LED and an LFO LED to indicate the rate.

Summary created by AI and may not be accurate. See original source.