Chuck D. Bones
Circuit Wizard
This is my 2nd entry in Buddy's Circuit Design Contest. It's a stereo chorus based on a pair of PT2399s. The idea is a spin-off from the Stereo Digital Reverb project. You can think of it as a stereo version of the Sea Machine, minus three knobs, with a better LFO and all of the filters corrected.
Sheet 1 shows the two delay stages. They are identical except for the resistors that set the delay time. I wanted their delays and sweeps to be slightly different for a deeper stereo image. The delays on both are in the 44ms range. Kinda long for a chorus, but it works. There is some feedback around each delay for a more lavish tone. The delay times are modulated by two LFO signals.
Sheet 2 shows the buffers, mixers, LFO and power supply. U4B is the input buffer. It supplies the DRY signal to the two delays and the mixers. U4A & U4D are the output buffers. VR1A & VR1B form a dual mixer. At 7:00, the signal is 100% dry, at noon it's 50/50 and at 5:00 it's 100% wet for a pure vibrato effect. The PT2399s and the LFO all run on +5V. U6 generates the LFO waveform. Switch S2 selects between two waveforms: smooth triangle and random ramps. The smooth triangle is only available in the CB mod of the STOMPLFO. You can also run a stock STOMPLFO chip and change R60 to 12K so you get the regular triangle waveform, or 7.5K to get the sine waveform. Apart from the random ramps, the other waveforms are not too useful in a chorus. U5 buffers and inverts the LFO signal so that the two delays are driven by LFO signals that are mirror images of each other. In other words, while one delay is sweeping up, the other delay is sweeping down. R53-R55 & C44 scale and filter the LFO signal. The cutoff freq was set low to limit how fast the random ramps can sweep. The SPEED & DEPTH controls have more than enough range. One could hook up the TAP pin on U6 to a momentary stompswitch.
Sheet 1 shows the two delay stages. They are identical except for the resistors that set the delay time. I wanted their delays and sweeps to be slightly different for a deeper stereo image. The delays on both are in the 44ms range. Kinda long for a chorus, but it works. There is some feedback around each delay for a more lavish tone. The delay times are modulated by two LFO signals.
Sheet 2 shows the buffers, mixers, LFO and power supply. U4B is the input buffer. It supplies the DRY signal to the two delays and the mixers. U4A & U4D are the output buffers. VR1A & VR1B form a dual mixer. At 7:00, the signal is 100% dry, at noon it's 50/50 and at 5:00 it's 100% wet for a pure vibrato effect. The PT2399s and the LFO all run on +5V. U6 generates the LFO waveform. Switch S2 selects between two waveforms: smooth triangle and random ramps. The smooth triangle is only available in the CB mod of the STOMPLFO. You can also run a stock STOMPLFO chip and change R60 to 12K so you get the regular triangle waveform, or 7.5K to get the sine waveform. Apart from the random ramps, the other waveforms are not too useful in a chorus. U5 buffers and inverts the LFO signal so that the two delays are driven by LFO signals that are mirror images of each other. In other words, while one delay is sweeping up, the other delay is sweeping down. R53-R55 & C44 scale and filter the LFO signal. The cutoff freq was set low to limit how fast the random ramps can sweep. The SPEED & DEPTH controls have more than enough range. One could hook up the TAP pin on U6 to a momentary stompswitch.
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