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So, after 20 years of wanting, we finally bought a Soundmaster SR-88 on fleabay.. Paid under a ton for it, in box with manuals, with START / STOP buttons already replaced, which was nice, but the STOP key is already gammy, so i may have to revisit that despite it looking like a pain in the hole to do.
First thing was to add the SYNC IN mod, so i could clock it with something else. It's 1 pulse per step - so for every cycle of a square LFO, it will advance a step. This 'beats' against the internal clock, so you can get some serious swing if You play your cards right. You can see the mod to the left of the mods picture attached - i enclosed it in heatshrink and just layed it over the board. It works very well with the usual suspects triggering it.
Now to the Sound mods. The Trimmer on the board works with the TONE pot, it's a 470k, so you need to get that out of there and wire in a 470k pot instead to start with. This acts as a low pass filter, including some odd feedback when both TONE and it are open..
Then i set off on the Bends (thick red cables).. They are all marked with coloured circles on the pic attached - just short alike colours together as it plays for fun. They mostly cause cross triggering of the voices, and are easy ON/OFF fun to send to switches, except the WHITE one - this needs to firstly be switched, then loaded with a pot, as it causes that crazy SQUAWK trick. Its best to experiment with the value of the pot, or bridge legs of what you have with different resistors to get the right range.. This mod is pretty extreme sounding, but worth doing right.. Mess till You find a good value that doesn't pack all the action in a small area near the end of the pot's range.
Next, the sound mods (thin wires).. These are marked in Cyan shading on the pic attached - the shade will cover the points that should be bridged with caps. Nothing too clever here, just adding in (non-polar) capacitors in parallel with ones already in the circuits to change lengths and such. Nice thing is, different values give different results, so some creative use of Multi-pole/Multi Throw switches and open up fun.. Grab a 103z and a 68n cap and poke about to get a feel..
I didn't use all of the mods marked on my unit, only what i could fit on switches i mounted in the battery bay, and by using the SQ out port. NOTE: if you choose to loose the SQ out, remember to short the 2 leads as they come off the board to the socket - they carry the audio for the cym sound!
First thing was to add the SYNC IN mod, so i could clock it with something else. It's 1 pulse per step - so for every cycle of a square LFO, it will advance a step. This 'beats' against the internal clock, so you can get some serious swing if You play your cards right. You can see the mod to the left of the mods picture attached - i enclosed it in heatshrink and just layed it over the board. It works very well with the usual suspects triggering it.
Now to the Sound mods. The Trimmer on the board works with the TONE pot, it's a 470k, so you need to get that out of there and wire in a 470k pot instead to start with. This acts as a low pass filter, including some odd feedback when both TONE and it are open..
Then i set off on the Bends (thick red cables).. They are all marked with coloured circles on the pic attached - just short alike colours together as it plays for fun. They mostly cause cross triggering of the voices, and are easy ON/OFF fun to send to switches, except the WHITE one - this needs to firstly be switched, then loaded with a pot, as it causes that crazy SQUAWK trick. Its best to experiment with the value of the pot, or bridge legs of what you have with different resistors to get the right range.. This mod is pretty extreme sounding, but worth doing right.. Mess till You find a good value that doesn't pack all the action in a small area near the end of the pot's range.
Next, the sound mods (thin wires).. These are marked in Cyan shading on the pic attached - the shade will cover the points that should be bridged with caps. Nothing too clever here, just adding in (non-polar) capacitors in parallel with ones already in the circuits to change lengths and such. Nice thing is, different values give different results, so some creative use of Multi-pole/Multi Throw switches and open up fun.. Grab a 103z and a 68n cap and poke about to get a feel..
I didn't use all of the mods marked on my unit, only what i could fit on switches i mounted in the battery bay, and by using the SQ out port. NOTE: if you choose to loose the SQ out, remember to short the 2 leads as they come off the board to the socket - they carry the audio for the cym sound!
NoT fOr ArMeR 
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