Recreation of the Bit-1, 99 or Bit-01 DCO, a crude sawtooth from a counter used to create the pulse wave and a triangle, two waves per waveshare. I’m adding a few extra functions as well, a dual channel DAC will provide CV 0-10v and velocity 0-5v from the received midi note for key tracking etc and the waveshare will also generate a gate and a trigger for the envelope generators.A dual comparator does the PWM and some transistor switches provide the triangle. It’s a pretty simple circuit, the waveshare handles detune , octave range and pitchbend over MIDI. Modulation is read in from an ADC inputs and I also want to add polymod of DCO1 from 2 on another ADC input.
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G’day @craigyb,
I don’t know if you’re on the synth-diy mailing list, but some chat about these circuits just went by.
You can check it out here.
Cheers
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Hi, That’s Tom from Electric Druid, we are in discussions about the design with him. Of course we are not using an 8253, effectively replacing that with an RP2040 to generate the square wave for the counter. It’s early days as I’ve not even written a single bit of code yet, what you can see is me firing a square wave from the Hagiwo DCO code at the counter circuit to test it’s abilities. Hence the low frequency of around 20-40hz even when playing a midi note of C6. PWM is now working and I will start some code soon.
I looked at the bit-01 about 3 weeks ago and thought I could build a clone of this, only thing stopping me was the rare static ram. But then I decided just to build the DCOs and mentioned it to my collab partner on this project and he intern had been speaking with Tom about it too.
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I was lucky enough to one a Bit 1 in the 80s and really lucky to have a roadie to move it. I’ve had cars lighter than the bit 1. I hope yours will be lighter. Cracking dco.
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I’ve never really owned or played one in earnest. I was planning to build a genuine bit-01 which is the rack version of the bit-1. But at the moment I just want to get a working dual DCO which I seem to have made good headway into today.
I’ve got DCO1 & 2 functional, playing notes in tune over MIDI, responding to pitch bend, glide commands, detune, FM inputs etc. octave selection over MIDI too.
I even managed to get the dual channel DAC and gate outputs working so I have pitch and velocity CV for the filters etc.
Detune needs to be moved to MIDI cc control to simplify building. The CV needs scaling properly for 1v/octave and the glide behaves strange in that when you send the note off by lifting your finger off the keyboard it jumps to the destination note, for me it should keep gliding, until it reaches its destination note or the key is pressed again. So I need to fix that.
I hope I can build an 8 note voice board in the next few weeks when I’ve decided on a suitable filter design.
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Got some lovely pads from the Bit 1
I’ve made some progress with the bit-1 clone DCO
Portamento now works as it should with a range of 0-10s on an exponential scale. MIDI CC is used for time and on/off.
Pitch bend range has been improved from 1 tone to 12 semitones and this can be adjusted from 0-12 with a MIDI CC message.
Octave range of each DCO can be set individually with a MIDI CC for each DCO
Detune is now set with a MIDI CC
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Created a little video of the functions
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