4hp
This is a design by Tom Hirst (who also designed the NLC Snake Joke module). His description for the design is:
“It's a vactrol-based multiplying-DAC (digital to analog converter). It basically naively uses vactrols as kind of switches to convert a 4 bit number to an analog voltage. But being a multiplying DAC it also takes a reference voltage so the output is relative both to the reference voltage and the size of the 4 bit number.”
It has 8 vactrols.
REF1 is preset via REF1 jack switching pin, so you can just turn up the REF1 pot if you want a static voltage or offset, then feed gates or CVs to BIT 1-4 inputs. The module is quite fun to use with modulating CVs or audio on the REF inputs. It is quite happy to accept negative going voltages on the REF inputs as well.
Using vactrols for DAC processing means it will be slow and slew, depending on the recovery speed of your vactrols. Consider this as a pattern generator or a somewhat strange VCA or, if you must, a DAC.
The spacing for the vactrols is quite tight. Don’t try to use the chunky VTL series. The Macron NSL-32 series will fit or DIY ones. I used DIY vactrols with GL5549 LDRs, but it is not so important which LDRs you use.
The RFB resistor adjusts the gain of the outputs, for GL5549 LDRs, I used 100k for RFB. You may need to adjust this to suit your choice of vactrols, Tom’s version used approx. 80k. If you find the output too small, increase RFB. If the output is too hot and hitting the rails, reduce it.
4hp
This is a design by Tom Hirst (who also designed the NLC Snake Joke module). His description for the design is:
“It's a vactrol-based multiplying-DAC (digital to analog converter). It basically naively uses vactrols as kind of switches to convert a 4 bit number to an analog voltage. But being a multiplying DAC it also takes a reference voltage so the output is relative both to the reference voltage and the size of the 4 bit number.”
It has 8 vactrols.
REF1 is preset via REF1 jack switching pin, so you can just turn up the REF1 pot if you want a static voltage or offset, then feed gates or CVs to BIT 1-4 inputs. The module is quite fun to use with modulating CVs or audio on the REF inputs. It is quite happy to accept negative going voltages on the REF inputs as well.
Using vactrols for DAC processing means it will be slow and slew, depending on the recovery speed of your vactrols. Consider this as a pattern generator or a somewhat strange VCA or, if you must, a DAC.
The spacing for the vactrols is quite tight. Don’t try to use the chunky VTL series. The Macron NSL-32 series will fit or DIY ones. I used DIY vactrols with GL5549 LDRs, but it is not so important which LDRs you use.
The RFB resistor adjusts the gain of the outputs, for GL5549 LDRs, I used 100k for RFB. You may need to adjust this to suit your choice of vactrols, Tom’s version used approx. 80k. If you find the output too small, increase RFB. If the output is too hot and hitting the rails, reduce it.
