converting a signals voltage range?


I am fixing an old electronic organ where the top octave generators are broken. I am trying to get a signal from Arduino to match what was originally sent from the IC's. In order to do that i have to convert a squarewave from Arduino going from 0 - 3.3 V to a signal going from -12 - 0 V. I am using the organs 12 V and -12 V supply.

Using an inverting amplifier built with a LM741 op-amp i got an OK result. The squarewave is not really square anymore but it has the correct range of voltage. I am wondering if anyone here has an idea for a simpler or more effective way to do this?



Thanks. I have never used optocouplers before, but it sounds like a good idea.

Do you know an optocoupler suitable for my purpose? My signal is a squarewave running at 9kHz and below.

Look at SFE web-site: Drawings: Swap Vcc and Ground with negative Vcc, if you don't need low impedance output , than increase resistors value 10x or 20x times.