Hi
You can see the topology of Tone2 Pro below.
From the topology you can see the volume can be controlled by two chips——DAC and NJU72315.
The difference between low/high/pre-amp modes is the volume of DAC and NJU72315.
You can see the relationship from the table below.
| DAC Volume | Analog Volume(NJU72315) | Balanced RCA Output① | Single End RCA Output① | 4.4 Headphone Output① | 3.5 Headphone Output① | |
|---|---|---|---|---|---|---|
| Low Gain | Fix to Maximum | Adjust from -12dB to -62dB | 4Vrms | 2Vrms | 0-2.5Vrms | 0-1.15Vrms |
| High Gain | Fix to Maximum | Adjust from 0dB to -62dB | 4Vrms | 2Vrms | 0-5Vrms | 0-2.3Vrms |
| Pre-AMP | Adjust from 0dB to -127dB | Fix to Maximum | 0-4Vrms | 0-2Vrms | 0-5Vrms② | 0-2.3Vrms② |
①Note: The results are built on the condition that the digital volume is fixed to maximum and the audio signal souce is 0dB.
②Note: The headphones’ outputs are varying from the RCA outputs.
In summary,if you want to use headphone Jack,I suggest you to choose the low or high gain mode according to the impedance of the headphone.If you want to connect to power amplifiter or active speaker,and the volume of the speaker can not be easy to adjusted,you can choose Pre-Amp mode.