The Soundmaster SR-88 is a simple analog drum machine, with four sounds (Bass Drum, Snare Drum, High-hat and Cymbals (the two latter work nicely as closed and open high-hats), 8 patterns and step-time only programming. It lacks a clock input, but does have a couple of clock outputs. Since it's often not practical to use the SR-88 as a master device in a setup, a sync input would be nice.
This page describes how to add a sync input to the SR-88. The diagrams are all drawn in ASCII, because this page was made from a posting I once made to a mailing list.
Well, this isn't a TRUE sync input, in that after the mod the SR-88 will not slavishly follow an external clock. Rather, the sync input functions a bit like soft sync on an analog synth, in that you can get the SR-88 to synchronize with an external source only if the SR-88 TEMPO control is adjusted properly. The upside of this is that you can sync the SR-88 to sources running faster or slower than the SR-88. The SR-88 uses one clock per step which is far below the 24/48/96 PPQN standards used by other machines, and in many instance you'll want to sync it to that, or even to something running slower (like running the SR-88 at 1/16th notes while the external source is running at 1/8th notes).
For instance, I've successfully synced my SR-88 to my Yamaha RX-11, which outputs a clock of 24 PPQN. Note however that it becomes more difficult to adjust the SR-88 properly the faster the input clock is relative to the SR-88, and that it will have to be re-adjusted for changes in tempo. So, not useful for live use perhaps.
The mod is designed to accept positive-going clock pulses. I've successfully synced it to a Sequential Pro-One and Yamaha RX-11.
The actual mod is very simple and involves adding a few components to the board. On the SR-88 board you'll find a 4011 CMOS NAND chip, and the mod is connected to pin 8 of this chip:
9 --\
...---| \
------- | /| | |o---...
sync in >--| 47k |-----|< |------*------| /
------- | \| | 8 --/
1N4148 | existing 4011 gate
|
+-...
When you open the SR-88 however, you'll find that the you've only got access
to the underside of the board, and although the board can be removed it's
a bit awkward (it's mounted using the front panel pot/switch nuts, and
input/output jack nuts, as well as using screws and being a general tight fit).
On my unit, I didn't want to add any extra holes for the external input
(there's not a lot of space in there anyway), so I decided to sacrifice the
external footswitch start/stop input. The ASCIIgram below is the interior
view when the bottom plate has been removed, showing this mod:
rear
-----------------------------------------------------------
| | |
| | SR-88 PCB |
| | |
| | |
| | 4011 pin 8 |
| | | |
| | | |
| | v 1N4148 |
| B | |\ | |
| | * *-----| >|---+ |
| A | * * |/ | | |
| | * * | |
| T | * * | |
| | * * | |
| T | * * | |
| | * * | |
| E | | |
| | | |
| R | --- |
| | | | |
| I | | |47k |
| | | | |
| E | --- |
| | | |
| S | | |
| | | |
| | * * * * |
| | \ |
| | *--* X b * * |
| | a | |
| | / |
| | / * * |
| | .../ |
| | |
-----------------------------------------------------------
footswitch output
Notes: Anyway, that's about it. Happy syncing!
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