ORIGINAL SCHEMATIC & OTHER INFORMATION: birthofasynth
STRIPBOARD LAYOUT
Original circuit uses LF442 and LM394 for the exponential converter. As you know, LM394 is obsolete and LF442 is hard to find these days, so I substituted LM394 with a matched pair of 2n3904s and LF442 with TL072. I have no significant issues so far.
'SKEW MODIFICATION'
The 'Skew' does nothing until it passes 12o'clock. If the 1st pin of 'Skew' potentiometer is connected to '-3v' instead of '-12v', it starts morphing the wave once you turns the knob. So I added a simple voltage divider as you can see above.
FACEPLATE LAYOUT
The dimension is 30mm(6hp) x 129mm
7mm hole : potentiometer (6ea)
6mm hole : 3.5mm jacks (7ea)
6mm hole : DPDT On-On toggle switch (1ea)
3mm : mounting screws
MEASUREMENT
Sine wave output: 9.99Vpp
Triangle wave output: 9.55Vpp
Pulse wave output: 9.95Vpp
Frequency range: 0.35Hz ~ 20.9KHz
Skewed triangle wave
Skewed sine wave
Happy to see your build of this VCO. I cheated and cloned the PCBs and have appearantly populated three of the five boards I had made. Ihave a bunch of XR2206 so I can add another one if I like.
ReplyDeleteNotice your suggestions for replacements of hard-to-find components but the LM394 are to issue either, However I had some 100k multiturn potentiometers I wanted to use but they "get lost" when getting above 40k, so I have ordered dual concentric potentiometers as I have ONE hole drilled in the panel.
Odd solution but may be interesting with coarse- and fine-tuning on one axle.
I will the next day(s) finish these modules by making the connections from the pcb:s to the panels, hoping the potentiometers will arrive soon. Also got two variations of Yusynths VCOs -2SC1583 and LM394. Are five VCOs too many???
/Magnus