[sdiy] TB-303 BTW

[Colin f]

> While on the subject of TB-303s...
> 
> I have one here that my buddy wants to have variable slide 
> time on. I  
> looked at the schematic and it looks like the DtoA and the slide are  
> sharing an opamp. Has anyone done this and figured a solution?

The 303 slide is a simple RC lag circuit.
The 'R' is the output impedance of the R-2R DAC.
An analog switch puts the capacitor either at the input or the output of the
op-amp that buffers the DAC resistor chain.
If the cap is at the input, you get slide as the cap has to charge through
the DAC resistance.
If the cap is after the op-amp you get no slide, and the voltage on the cap
is maintained at the current note CV so it's at the right starting point
when the slide is turned on.
If you want variable slide, you could fix the cap after the buffer amp, but
fed via a variable resistor.
Then re-wire the analogue switch to bypass the variable resistor when the
slide is off.
Should be possible with a couple of track cuts and fly-wires.

Cheers,
Colin f