A small mod for the Roland SPV-355 Synthesizer

    I was recently helping a friend repair his SPV-355 and he asked if it might be possible to add "release" to the envelope generator.  A quick look at the schematic revealed that the circuitry needed (a switch to ground that turned on when the gate signal dropped) was already present, in the form of Q50 and Q51.   But no variable resistor was provided, so release was immediate.  He suggested using the Decay slider, which I guess is what was also done on the Minimoog.   This ended up being a very easy mod, as you simply need to remove one end of R340 from the pc board, and connect it to one end of R337.   Below you can see a photograph of the mod and also the schematic for what we did.  Of course, now the decay slider controls both decay and release times.


  Please note: Performing this mod to your synthesizer is done at your own risk, and  should only be attempted by someone familiar with this type of work.  I will not be responsible for any damage to any instrument caused by either proper or improper use of the information offered here. 


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