The Grand Orbiter Phase Machine is a four-stage OTA phaser, with options for vibrato or phasing (a bit like a Univibe).
Not exactly a small board, but not too much to take on either. MLC caps might be a good idea for some of the 1uf caps to save space.
Currently unverified. I have reviewed the schematic a couple of times, and two errors have been found and corrected, but still... it's a huge board. What could go wrong, right?
EARTHQUAKER DEVICES GRAND ORBITER PHASE MACHINE - VERO LAYOUT
This layouts got some issues - missing the 100k to ground in the voltage divider with the 220k on IC3. There's probably some other issues as this didn't solve the problems - basically the LFO wasn't oscillating. It was passing signal and the sweep pot swept the frequency, but no modulation.
ReplyDeleteNot that it matters, but the cut side of the layout is missing some of the links, too.
Thanks Mike - I've updated the voltage divider, and will check over again for any other errors.
DeleteIt was also missing a link between 12 and 10 on IC3 - which happens to be part of the LFO.
DeleteYeah, I added that one too and it still didn't want to seem to work. I went through the schematic and layout as best I could and didn't see anything else that jumped out to me, but I'm probably missing something. Their may have been something with the TL074 pins 12/13/14 that wasn't quite right, but I couldn't isolate it - and it may be something earlier in the circuit not behaving.
DeleteRight - do you have a multimeter to check voltages and an audio probe? And did you notice that the TL074 is upside down on this layout? I'm assuming you did, but just ruling that out.
Delete12, 13 and 14 look OK in terms of matching the schematic, and it's one of the simpler parts on the board.
Unfortunately, I bailed on the board and already pulled pots and the 1uF films for another project - I wasn't really anticipating getting a reply this quick. On the probe, I was getting signal on Pins 5 & 12 for IC 1 & IC2, voltages looked correct on the TL074 - IIRC, I know ground and +v was good, and I had the 1/2 supply bias voltage on at least pin 5, not sure if I checked the others... But can't quite remember. It's also entirely possible that I had another error in the build after adding the 100k and connecting 10 & 12 on IC3. I just wasn't getting any change in the LFO voltage after making those 2 corrections.
DeleteFair enough - I know the feeling. There's a verified layout for this over on dirtbox layouts if you are still keen. I hadn't got around to making this one yet, as I often get distracted with other projects.
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