Alrighty .
i promised a more detailed explanation on the SY-1 mods i did.
and since i just opened her up for some minor repairs and adjustments,
and since opening her up is a PITA,
and since opening her up is a PITA,
now seems to be as good a time as any.
oh yeah - in NO WAY can, should or will i be held responsible for any damage this (or you) may do to your unit. or its resale value, for that matter.
capice? we cool.
capice? we cool.
* first off, the easy bit: the dual mono output.
looking at the schematic, channel 1 and channel 2 are added into a single mono signal using two 10K resistors, after the volume sliders. (they left out CH2's volume slider for clarity.)
so you can just lift a leg on CH2's 10K resistor and run an extra wire to the ring of the jack. the tip stays connected the way it was, using the original wiring.
A WORD OF WARNING: this does mean that the SY-1 is now configured for use with stereo (TRS) plugs.. when you plug a mono jack cord in there, you will only ever hear ONE CHANNEL.
you'll be pulling CH2 to ground = no sound !
* next up, the fun bit: CV control.
i did some modifications to what i had in this earlier post - and lo and behold, things just got simpler!
see, even with the added bonus of the service manual, i don't seem to be able to locate the 4.7K pulldown resistors - they're in the schematic, but they don't seem to be on the board.
(unless i really am missing something. if so, feel free to drop me a line.)
see, even with the added bonus of the service manual, i don't seem to be able to locate the 4.7K pulldown resistors - they're in the schematic, but they don't seem to be on the board.
(unless i really am missing something. if so, feel free to drop me a line.)
i blindly put in 5.6K's at the time - closest value layin' around - but since i doubt they were in there in the first place, and since they lowered the CV input's impedance quite a lot, i took them out.
well, the net result is far better range!! with some careful adjustment, i was able to get a very decent tracking of the full 5 octaves my MIDI to cv converter will give me. yay.
well, the net result is far better range!! with some careful adjustment, i was able to get a very decent tracking of the full 5 octaves my MIDI to cv converter will give me. yay.
so, updated schematic:
for the record: i'm assuming you never want to be able to use the tune pedal again, just CV in.
now, originally, a fraction of the +9v from the tip got sent back in through the ring connection. therefore, we can use the ring for CV input.
BUT you'll want to lose the +9v connection first - just remove the 100R resistor. it makes it safer against accidentally plugging in mono jacks - which will happen eventually, trust me - and it frees up the tip for CV input use.
of course, for CV input, the easiest way is to plug a jack in halfway, thus using the ring of the tune pedal jack as is.
not exactly a stageproof method, though.
a better solution would be to run your CV on the tip instead of the ring.(*read on first.)
you'd need to do a tracecut on the pcb: cut the connection going from the ring to the brown wire (near the power jack). the brown wire takes the CV to the oscillators.
leave the ring floating, and connect the brown wire to the tip (duh.)
BUT
more importantly, you'll want to replace the original 47K resistors with a higher value to adjust tracking.
you can find them here:
right now, 120K gets me in the ballpark for a nice range of V/Oct control, but even though i have the service manual i still haven't gotten round to calibrating my unit yet - so that value might change after calibration.
a trimmer is definitely the better option here anyway, trust me.
now i guess you could put in two 250K precision trimmers and get it over with - but i went and took out those resistors, ran wires from the holes, added a 100K trimmer in series to each of the original 47K's, and mounted the lot on a piece of perfboard that fits right next to the jack PCB. (only real space left in there.)
that gives me the advantage of being able to adjust the trimmers more easily, as they're a bit more reachable, even though it still means disassembling the case.
damn, i wish i'd taken pictures of that piece of perf before closing her up again.
(*) now, if you're like me, you might want dual CV inputs for fully independent channels.
first off, dual inputs means using a split stereo cable for both tip and ring (see output jack mod), which means that you should leave that ring connection intact - no tracecuts needed. we will keep CV for CH2 on the ring input, so the channels correspond with the output jack.
you can go straight to replacing CH2's 47K resistor as per the above procedure.
the second input, tip to CH1, uses only one of the 47K's resistor holes.
run a wire from the jack tip (you did lose that 9v, right?) straight to the 47K+trimmer combo (or 250K trimmer, or whatever you came up with). the wire coming out of the trimmer should then go to the appropriate resistor hole, which is CH1's CV mixer line.
that would be the hole closest to the board's edge (CH1 resistor's left side in pic above.)
now, originally, a fraction of the +9v from the tip got sent back in through the ring connection. therefore, we can use the ring for CV input.
BUT you'll want to lose the +9v connection first - just remove the 100R resistor. it makes it safer against accidentally plugging in mono jacks - which will happen eventually, trust me - and it frees up the tip for CV input use.
of course, for CV input, the easiest way is to plug a jack in halfway, thus using the ring of the tune pedal jack as is.
not exactly a stageproof method, though.
a better solution would be to run your CV on the tip instead of the ring.(*read on first.)
you'd need to do a tracecut on the pcb: cut the connection going from the ring to the brown wire (near the power jack). the brown wire takes the CV to the oscillators.
leave the ring floating, and connect the brown wire to the tip (duh.)
BUT
more importantly, you'll want to replace the original 47K resistors with a higher value to adjust tracking.
you can find them here:
right now, 120K gets me in the ballpark for a nice range of V/Oct control, but even though i have the service manual i still haven't gotten round to calibrating my unit yet - so that value might change after calibration.
a trimmer is definitely the better option here anyway, trust me.
now i guess you could put in two 250K precision trimmers and get it over with - but i went and took out those resistors, ran wires from the holes, added a 100K trimmer in series to each of the original 47K's, and mounted the lot on a piece of perfboard that fits right next to the jack PCB. (only real space left in there.)
that gives me the advantage of being able to adjust the trimmers more easily, as they're a bit more reachable, even though it still means disassembling the case.
damn, i wish i'd taken pictures of that piece of perf before closing her up again.
(*) now, if you're like me, you might want dual CV inputs for fully independent channels.
first off, dual inputs means using a split stereo cable for both tip and ring (see output jack mod), which means that you should leave that ring connection intact - no tracecuts needed. we will keep CV for CH2 on the ring input, so the channels correspond with the output jack.
you can go straight to replacing CH2's 47K resistor as per the above procedure.
the second input, tip to CH1, uses only one of the 47K's resistor holes.
run a wire from the jack tip (you did lose that 9v, right?) straight to the 47K+trimmer combo (or 250K trimmer, or whatever you came up with). the wire coming out of the trimmer should then go to the appropriate resistor hole, which is CH1's CV mixer line.
that would be the hole closest to the board's edge (CH1 resistor's left side in pic above.)
now hook up your CV keyboard, and turn the trimmer until you get a decent in-tunish response over a couple of octaves.
that's about it - proceed with caution and have fun!
that's about it - proceed with caution and have fun!
