CGS D/A converter
CGS11 the CGS D/A converter board was really developed for Ken Stone's own use, to allow HIS 486 based sequencer to connect to various VCOs etc. It has twelve bit resolution, and four "gate" outputs, though these only output around 4.5 volts maximum.
The design of the board here has not been tested.
How to use this module
This module is designed to connected to either a 16 or 8 bit bus, and contains two latches that can be latches independently. For a backplane/bus common stripboard may be used, along with 0.1 pitch 90° headers. It can be used with the parallel port adapter for IBM PCs parallel port adapter], which is how Ken used his. Software is up to the individual.
While untested, the analog portion of the module should work on 12 volts. The digital portion requires 5 volts.
A little on how it works
Ken avoided using commercial D/A converters for a few reasons, including stability, and availability.
Construction
Before you start assembly, check the board for etching faults. Look for any shorts between tracks, or open circuits due to over etching. Take this opportunity to sand the edges of the board if needed, removing any splinters or rough edges.
When you are happy with the printed circuit board, construction can proceed as normal, starting with the diodes and resistors first, followed by the IC sockets if used, then moving onto the taller components.
Take particular care with the orientation of the polarized components, electrolytics, transistors and ICs.
When inserting the ICs in their sockets, if used, take care not to accidentally bend any of the pins under the chip. Also, make sure the notch on the chip is aligned with the notch marked on the PCB overlay. Please note that the CMOS chips are static sensitive devices, so make sure you handle them correctly.
Parts list
This is a guide only. Parts needed will vary with individual constructor's needs.
| Part | Quantity |
| Capacitors | |
|---|---|
| 100n | 3 |
| 10uF 25V tant | 3 |
| Resistors | |
| 1k | 5 |
| 10k | 2 |
| 22k | 1 |
| 47k | 1 |
| 100k 1% | 19 |
| 200k 1% | 13 |
| Semi's | |
| 4050 | 2 |
| TL072 | 1 |
| BC547 | 4 |
| 74LS374 | 2 |
| Misc | |
| Ferrite bead (or 10R resistor) | 2 |
| CGS11 PCB | 1 |
Notes
- Fast 74xxxx CMOS latches with the same pin configuration can be used in the circuit.
- Different latch chips with the same pin configuration can be used in the circuit. The obsolete 74LS273 can be used if A is linked to B instead of D. Check your data books.
- 10 to 22 ohm resistors can be used instead of the ferrite beads. If you don't care about power-rail noise, just use a link instead.
CC-BY-NC
Readers are permitted to construct these circuits for their own personal use only. Ken Stone retains all rights to his work.
See also
References
- D/A converter for music synthesizers. by Ken Stone, 2001, with permission of the author - archived
External links
- CGS Synth discussion group, for discussion of locating parts, modifications and corrections etc.