This board offers various utility features for a two-VCO-voice. It is designed to be used together with two [../vco_mk1/](VCO mk I boards) and offers the following features:
- voltage controlled filter
- voltage controlled amplifier
- simple mixer
- 2x square_ctl signal processing (buffering, sync pulse generation, clamping, which are missing from the VCO mk I board)
- an expo converter (to be used as VCF input)
- a 2-channel MCP4822 DAC for VCO control voltage generation
- three general-purpose RC low pass filters
The gerber outputs used for fabrication with JLCPCB are
located under fab/.
The fabrication layers indicating which component values to put where are here.
rev01 has no marking at the wind fish logo. It has been fabricated
using the gerber outputs in fab-rev01/. Please refer to the errata
below.
rev02 can be identified by a "rev02" text close to the wind fish logo. It has never been fabricated as it only contains silkscreen and component value fixes.
Some resistors in the sync pulse circuitry are wrong. R48 and R49 must be changed from 10k to 1k. R50 and R51 must be changed from 1k to 10k. This has been fixed in rev02.
R53 and R54's values are too weak, leading to very bad DAC performance (e.g., non-monotonic DAC behaviour every 4 code points). Maybe a 100k poti would work better; I fixed it by de-soldering the potis and wiring U2's DAC output pins 6 and 8 to the connector J4 directly.
R53 and R54's values are too weak, leading to very bad DAC performance (e.g., non-monotonic DAC behaviour every 4 code points). Maybe a 100k poti would work better; I fixed it by de-soldering the potis and wiring U2's DAC output pins 6 and 8 to the connector J4 directly.