The second picture shows the audio output stage of the cost reduced VIC-20. R8 (1KOhm) and C10 (100nF) form the same single pole passive RC network with cutoff frequency 1.6kHz. As with the original VIC, the cutoff frequency can be moved to 16kHz by replacing C10 with a 10nF capacitor.
The effect of this filter is to reduce the level of high frequencies in the VIC's sound output. By moving the filter cutoff to 16kHz, the high frequencies can be retained and the overall sound is brighter.