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The custom chips inside the DX7 made this possible at an affordable price. The modulating signal changes the phase (and thus the frequency) of the carrier, creating complex harmonic structures. The idea is that you start with a sine wave (the carrier signal) and perturb it with another signal (the modulating signal). Instead of the analog oscillators and filters of an analog synthesizer, the DX7 generates sounds digitally, using a technique called FM synthesis. The DX7 was the first commercially successful digital synthesizer, using a radically new way of generating sounds. Other functional blocks apply the envelope, hold configuration data, and buffer the output values. The sine and exponential functions are implemented with lookup tables in ROMs. I'll outline the other functional blocks briefly.Įach of the 96 oscillators has a phase accumulator used to generate the frequency. In this blog post, I'm focusing on the highlighted functional blocks: the operator computation circuitry that combines the oscillators, and the algorithm ROM that defines Unlike modern chips, this chip has just one layer of metal, visible as the whitish lines on top.Īround the edges, you can see the 64 bond wires attached to pads these connect the silicon die to the chip's 64 pins. The die photo above shows the DX7's OPS sound synthesis chip under the microscope, showing its complex silicon circuitry. Click this photo (or any other) for a larger version. Die photo of the YM21280 chip with the main functional blocks labeled.