1. The tone-control knobs are not working?

Please check if the TONE button is set to PURE mode. PURE is the mode where the signal bypasses the tone circuit. Switching to TONE mode should enable the tone adjustment.

2. Why is the power indicator light flashing continuously after turning on?

The flashing power indicator light indicates low batteries. Please charge the device promptly.

3. Is the SK01 a preamplifier and headphone amplifier? Does the tone knob control only the 3.5mm audio output or also the headphone output?

The SK01 is both a preamplifier and headphone amplifier. The tone knob controls both the 3.5mm audio output and the headphone output. When adjusting the 3.5mm audio output of the SK01, it functions as a preamplifier, connected to a power amplifier, and allows adjustment of the high, mid, and low frequencies of the audio system.

4. Why am I not experiencing the Loudness effect?

Loudness is an equal loudness switch designed to compensate for the frequency response of human ears at low volumes. When listening at low volumes, our perception of high and low frequencies may be reduced. Loudness compensates for this by boosting high and low frequencies, aligning perceived loudness with the actual volume.

5. Why is the signal indicator light not turning on?

The signal indicator light indicates the volume level. It starts flashing as the volume increases (output voltage reaches 2V). The purpose of the signal light is to let you know if the volume is too high before wearing headphones. If the signal light continues to flash and is bright, it is recommended to lower the volume before wearing headphones, and then adjust it to your desired level, ensuring the protection of your ears.

If you have any further questions, please contact our support team at support@fosiaudio.com.