Bass response

The third generation iPod had a weak bass response, as shown in audio tests.[39][40] The combination of the undersized DC-blocking capacitors and the typical low-impedance of most consumer headphones form a high-pass filter, which attenuates the low-frequency bass output. Similar capacitors were used in the fourth generation iPods.[41] The problem is reduced when using high-impedance headphones and is completely masked when driving high-impedance (line level) loads, such as an external headphone amplifier. The first generation iPod shuffle uses a dual-transistor output stage[citation needed] rather than a single capacitor-coupled output, and does not exhibit reduced bass response for any load.