FIRST NIGHT IN THE PAST
AUG ‘26
FIRST NIGHT IN THE PAST
MODULATED PT2399 DELAY
FNITP is a delay based on a handful of common schematics available. While not an exact clone of any one delay pedal, it takes inspiration from several modulated PT2399 delays.
A PT2399 delay chip sits between two op amp buffers and features the common controls: delay time, repeats or feedback, and delay level or mix. The modulation is controlled by an opamp LFO with depth and rate controls.
LED/LDR Info:
Don’t use a vactrol. There isn’t space on the board. Roll your own. It’s fun. Or, just leave the LED/LDR unwrapped, pointing at each other or not, don’t stress over it. A helping-hands makes this easy to assemble. The exact color of LED (red is fine) and range of LDR aren’t essential here, modulation can be acheived with any combo of the two.
Put one the the two parts, LDR in one side of the helping hands horizontal to the table. Slide a little bit of heat shrink, less than a half inch, maybe a centimeter, onto it down onto the legs. Place LED in the other side of the helping hands, parallel to the table. Arrange them facing each other a few mm apart and slide the heat shrink over both the LED and LDR. If you cut it a little too small and don’t want to cut again just make sure the LDR is covered completely, a little LED showing out the bottom isn’t a deal breaker. If you don’t have a heat gun you can use a lighter, just keep the flame off of the heat shrink or it will burn.
There is an LFO rate indication LED that you can install or omit depending on you preference. This would be installed on the other side of the PCB, despite the silkscreen being on the same side. The LFO rate LED shows an inverted waveform. The original idea was to create a sort of uneven LFO, with every other peak at a different maximum. This being created by one LED next to, and pointing directly at, the LDR and the second LED being just some ambient light inside the enclosure. It didn’t work out so well because there is some overlap of the LEDs being lit and therefor some constant light hitting the LDR, causing the wave to never hit it’s lowest point. Maybe a square wave would acheive this instead of a traingle wave. I left the second LED on the board incase anyone wants an external LFO indicator or if anyone else wanted to trying something silly too. Fortune favors the bold or whatever. If you don’t care about an LFO indicator, or getting silly, just omit R28 and LED2.