Pearl SY-1 mods explained

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,

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.

* 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 !

i found insert cables (stereo to 2x mono, you know the type) to be easiest, but ymmv.

* 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.)

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.

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 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!

Remörk live in brussels, oct 24 2013

here's the set i played opening up for Deafheaven.
i came in as a last minute Pharmakon replacement, who was unable to play due to sickness..
too bad, would've loved to see a Pharmakon show.

with not too much time to prepare things, i decided to recycle some old 4track tapes, field recordings and melodies i'd used on previous shows and releases, and to pile some new stuff and improv on top of that.

conclusions of the day:
* murphy was right - prepare all you want.
* i prefer pink over white noise
* singing a Van Morrison song in front of a black metal audience isn't necessarily going to make you a lot of friends.

Condor Gruppe live @ Studio Brussel radio

new band, and a chance to use that Hohner Bass 3. yay!

Pearl Syncussion pt.II: Service Manual!

good news for everyone looking for the SY-1 schematic - a high res scan of the service manual is finally available!
download it here.
the whole thing provided by mister James Wetzel in Chicago, who had the bright idea to simply email the people over at Pearl. now how come no one thought of that before? weird.

James had this to say about the exchange:
 'Funny thing is the guy at pearl that i spoke with on the phone, gene okamoto, was super friendly and said something like "Pearl Syncussion...... Aha, now that's a name I haven't heard in a long, loooooong time." It was like the scene in star wars when obi-wan reacts to luke calling him obi-wan...
(...) and gene seemed to get a kick out of hearing the word "syncussion". '

well, there ya go, james. and gene. syncussion. hehe.

the above is a snippet of an email i got from james to ask for more info on the mods i did..
so i'm considering putting up a better mod guide now i have the service manual. stay tuned!

DD-14 again

hey hey, look what i found tucked away in a remote corner of our vast mansion.. if it isn't the old yamaha DD-14!
blew the dust off and took r for a little spin. first time i tried the MIDI functionality (that crapped out). noticed that CV can also control the foot pedal - hadn't thought of that before.

compared to all the possibilities in this piece of kit, the following recordings are extremely sober.
guess i'm minimal like that, yo.
more to come, i would think.

Pearl Syncussion

some time ago, i scored an SY-1.
on a fleamarket.
i won't anger you with the price.

after using it for a while now,  i must say i love the sound range this thing has - but it lacks a little in the control department.
i guess my main complaint about this thing is that there's two completely independent voices, with seperate triggers, but they get treated like a single entity. for one, their outputs get summed to a mono signal. so no way of processing the voices separately. that's a bummer.
to further that approach, external pitch control also applies to both voices.
and, to top it all off, the only way to control that pitch externally is through a footpedal or potentiometer. not quite the most accurate way there.

and then i came across this video:

where the thing is modded to track CV! now there's an idea. WANT.

so. the search begins.
only schematic to be found is a crummy, hardly readable piece of bluhh.

might as well just open up the case.
first thing i noticed is that ALL jacks used are stereo. good news, since the schematic shows that both voices get summed all the way at the end, using just two resistors. hooray for soon-to-be split stereo!


now, the tune jack is also a stereo one. the tip sends +9v to your footpedal, the ring returns the diminished voltage.

so if you want to run CV into yours, use an insert / stereo to dual mono cable, and use the end that doesn't have a voltage on it, ok? 

upon which you'll probably find much the same as i did - it does repond to external cv, but not quite as one would like. response to both expo and lin seems way out. 

turns out it does track quite consistently, but not 1V/oct - more like 0.4V/oct or something.
a simple voltage divider network (or an attenuator on yr modular) could do wonders here. drop your voltage a little and you should be good to go.

i decided to do that inside of the SY-1, so it not only becomes compatible with other CVstuff, but i also get to use the stereo jack to control both channels independently. i'm never gonna use the footpedal control anyway, so i can safely lose the 9v connection.

here we go:

ta-daaa. nice dual channel CV controls, trimmable to play in tune over about 3 or 4 octaves.
that's more than most drummers.

one option i looked into was changing the feedback resistor on the opamp mixer, but as you can see that would have affected the response for the front panel tune slider, the S&H, LFO and EG. didn't seem like the way to go. i also tried a simple resistor divider at the front end, but this seemed like the more elegant solution.

(EDIT: SCHEMATIC SIMPLIFIED AND IMPROVED.)

only thing left to do was use the stereo output jack in it's intended form - aka NOT mono -
and now i've got a true dual percussion synth. aces.

and although it looks quite easy on paper, i must say the good folks at Pearl really did build this thing like a tank. build quality second to none, with hardly any room left for mods.
glad i managed the lot without having to drill the case..