Stereo Delay PT2399 with chopper and downsampler - diy atmega8 microcontroller

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Stereo Chop Dub Delay Took about a week to build it. I always wanted to make something out of a broken but cute fadermixer i bought for 1 EUR. And i wanted to experiment with the PT2399 delay chip. And i wanted a hardware downsampler. And everthing should be in stereo. And midicontrollable. So this is the result. A stereo delay with a downsampler and additionally a simple gater. It might have been useful to make the configuration (Delay-SampleHold-Chopper) changable to Chopper-SampleHold-Delay or SampleHold-Delay-Chopper or ... but the veroboard quickly got quite full and it was difficult enough nevertheless.	old mixer from UK with good hardware and builtin PSU ... and 'faders' - i love faders :)
Delay Unit After stumbling over the PT2399 delay-chip and being positively surprized by web-demos on delays built with it, i ordered some via #bay quite cheap from china. They arrived 3 weeks later. I breadboarded the wellknown and excellent "Echo Base"-scheme and experimented a bit with feedbackfiltering. First i wanted to make a treble/bass-control like the cool bugbrand-delay has but wasnt quite succesful. I ended with a fixed bandpassfilter (in the feedbackloop) which can also be switched to a more 'full range'-feedback frequency range. Scheme of my feedbackpath to the right. I did not install the clipping diodes, i liked it better with distortions. Both are led through an opamp, scheme to the right. The veroboard got quite full, i needed to make the LFOs for the delaymodulation by the controller, they are output by PWM and can run in sync or slightly different to have a deeper stereo effect. The LFO-Voltages can also be controlled by midicontrollers, don't know if this might somehow come out useful... What i definately wanted to have on it, is a momentary switch to shortly enable a signal going into the delay. The delay output is NOT cut by this switch. That means when you press the switch e.g. just for the duration of a snaredrum, then just the snare goes into the delay and is repeated, the rest of the beat before and after the snarehit stays dry. This switch can also be 'pressed' by midinote. Here are 2 more or less useful examples. The device is still 'work in progress' and has some hardware bugs (not really stereo, downsampler to loud, downsampler should better be positioned before the delay...) some noolding of chopdelay with prophet08 - this is the same example as in the video chopdelay with Vermona ER9 - downsampler and momentary delay midicontrolled by sequencer	schematic of active feedbackpath with switchable bandpass
Downsampler A simple sample-and-hold unit, driven by a clocksignal from the µController. Left and right got individual clocks to receive cool stereo effects. The clocks can be set with the sliders or by midicontroller. The downsampler also has a momentary switch to selectively enable the effect on short passages, of course this is also possible by midinote.	schematic of downsampler
Chopper or Gater This is just 2 electronic switches (4066) driven by the µController. When open the signal passes, when closed, well... A clock perodically opens and closes the switches. Another pot sets the time it stays open. The clock can be set widely up resulting in ringmodulationlike effects, although there is a limit due to processortiming and my not-so-perfect programmingskills. (The mainloop could certainly run much faster if it would be optimized). The clock also can be synched to 8th or 16th notes, listening to miditicks (96 per bar).