an experimental EQ circuit based of the TL082 datasheet. i modified it to use a 9V battery, but could probably still use some work in terms of efficiency… as most things. nothing is ever finished really. the mid portion has a pretty high quiescence. fine tuning, of course, can be done with the resistor values and more dramatic differences by adjusting the cap values. if you happen to build it, shoot me an email and let me know what you changed or decided to change.
also keep in mind that the TL082 is a little noisy, so 6dB of highs will add in some noise. i kind of like it myself, but the TL072 is a better choice from what i understand.
here’s an update on the new additions/approach to the Mellotronium. i’m attempting to redo the SD card routines once i get the functionality added. using the SD library just doesn’t work right when reading byte values at 8kHz. i’ve looked into the WaveHC library with the most success, but had to modify not to use an external DAC. a new wav file playing solution from the SD card will have to be found.
without the clunky SD lib, program space has opened up… a lot of it in fact. now i’ve started using a wavetable. this video just has a single sine wave, but it’s modulate with the LFO and its seven different waveforms not to mention an amplitude modulating ADSR filter.
the breadboard to the side contains an experimental active 2-band EQ (TLO82-based) which needs some work. if anyone has any experience with this, i would love to know why the schematic in the datasheet doesn’t work at all. i wound up having to recall the usage from a different schematic where you make a voltage divider from and peer it into the positive terminal on both opamps. it works… in a way. i think i’ve inverted the wave form or something strange. it also sometimes works better as a radio than an EQ which i think i like. it made for some interesting heterodyning.