13.Instructions for the system settings-audio menu
1. I2S-OUT switch
When using the I2S-OUT port, please enable the I2S-OUT switch in Settings > Audio menu, which is off by default. Once the I2S output switch is enabled, the device’s analog output path will be disconnected, supporting only digital signal output.
2.OPT/COAX output
Control the optical/coaxial output port, the default state is OFF.
3.SPDIF OUT
This setting needs to be adjusted only when using coaxial output
In D2P mode, playing PCM signal will output native PCM signal; playing DSD signal, the system will convert DSD signal into PCM signal to output
In DoP mode, PCM signal and DSD signal will be natively output.
[Note] DoP is preferred. D2P needs to be selected when some devices do not support DoP.
4.LO output mode
The output mode setting allows you to configure the analog output port as either “Line Output” or “Adjustable volume at PRE-OUT TERMINALS”. Line output mode provides a fixed output level that is not affected by the volume, while the Adjustable volume at PRE-OUT TERMINALS mode is adjustable and controlled by the volume.
5. Lowpass filter mode
There are six different filters on the S15. You can choose them according to your listening preference.
6. Bluetooth Audio encoder
The default codec for Bluetooth transmission is the highest supported codec, and you can select the supported codec through this setting.
- Bluetooth Audio LDAC Encoder: Playback Quality
If you experience playback anomalies when using LDAC Bluetooth transmitting, you can adjust this option to balance the audio and connection quality.
8.Bluetooth Audio LHDC Encoder: Playback Quality
If you experience playback anomalies when using LHDC Bluetooth transmitting, you can adjust this option to balance the audio and connection quality.
9. Bluetooth volume adjustment mode
This function is only available for Bluetooth transmission, which features “Sync Bluetooth volume” and “Indep Bluetooth volume”. The Sync Bluetooth volume should also be supported by the receiving device, otherwise, it will be unavailable. The Indep Bluetooth volume means the volume adjustment of the receiver and transmitter is independent of each other. The Sync Bluetooth volume mode can solve the issue of overly small volume when connecting to some Bluetooth headphones, such as AirPods.
10. Balance
Channel balance means, by adjusting the output amplitude of the left or right channel individually to build up a special listening condition suitable for the users. For users who have no difference in hearing between left and right ears, there is no need to use this function, as the output of the left and right channels of the device is balanced. The default value of channel balance is 0, each of the left and right channels can be adjusted by 20 levels, and each level has a fixed difference of about 0.5dB.
11. All to DSD
After turning on the All to DSD, the global PCM audio will be converted to DSD for output, and the sound quality will be further improved.
[Principle] The most important thing of All To DSD is to convert the digital signal in PCM format to DSD format, so that the DSD format can be used when performing D/A conversion to obtain different styles of sound, more clear and natural sound. In addition, since the lowest DSD format is DSD64, which is 4 times the data of 44.1k/16bit only calculated from the amount of data, All to DSD is also equivalent to up-sampling the PCM signal. The effect of All to DSD also supports third-party apps.
12. Equalizer
The global PEQ function supports EQ superposition of the FIIO Music and other third-party apps. Here are the processes after enabling the PEQ on the system.
(1) Over 192k sampling rate- SRC processing;
(2) Priority: All to DSD>PEQ>MQA.
