Audio

The Neotron 32 generates mono pulse-width-modulated (PWM) audio with 8-bit centre-aligned pulses at a frequency of four times the horizontal video scan rate (giving roughly 151,500 samples per second). At the end of each scan-line, a new 8-bit PCM sample is generated by summing the outputs of three basic wavetable synthesisers. That PCM sample is fed to the PWM hardware at the start of the next scan line (to reduce jitter) and it gets played out four times during that scan line, giving an effective sample rate of just under 38 kHz. The hardware then consists of a simple low-pass filter to remove the PWM carrier frequency, and a headphone jack. As the SoC can't drive a large amount of current, amplified speakers are required.

Each of the three channels on the wavetable synthesiser can produce a square, sawtooth or sine waveforms, or random noise, at a selected frequency. There is also a rudimentary volume control for each channel.