Architecture


Design Philosophy

We want the device to work as a universal DAC/AMP for both high-sensitivity IEMs as well as high-impedance open-back headphones. We want it simple, small, yet but powerful. In addition to the sound quality and the maximum output power, we also need to consider the battery time as well, concerning the nature of the device.

We've tried many DACs and Amplifier ICs and found ESS9218p is the best option for our goal. Besides the sound quality, the primary advantage of ESS9218p is that the built-in amplifier delivers the maximum output voltage up to 2V RMS. Furthermore, it supports the 1V RMS option at the same sound quality to save power consumption.

For high-sensitivity IEMs, the amplifier noise figure is the most important. The high-sensitivity IEM is so sensitive that it translates every electrical noise or thermal drift into audible acoustic sound, usually white noise.

On the other hands, the high-impedance headphones require a higher power amplifier. Those headphones usually have low sensitivity, and they are free from the white noise affected by the amplifier noise characteristics. Instead, they need higher power from the amplifier output to deliver enough loudness and headroom.

We designed the software and the app to provide full access to every internal option of ES9218p.


3.5mm Unbalanced (Single Ended)

1VRMS Mode

For the most IEMs, The 2V RMS output would be too much. The 1V RMS mode offers the best power efficiency at the same sound quality as the 2V RMS mode.

2VRMS Mode

For low sensitivity IEMs or headphones, the 2V RMS mode delivers enough headroom and loudness.


2.5mm Balanced (Full Differential)

2VRMS Mode

The full differential direct audio path delivers the best linearity and separation, still with enough battery time.

4VRMS Mode

The maximum output power


Summary

4 types of output mode:

  • 3.5mm Unbalanced with single DAC 1.0V RMS
  • 3.5mm Unbalanced with single DAC 2.0V RMS
  • 2.5mm Balanced with dual DAC 2.0V RMS
  • 2.5mm Balanced with dual DAC 4.0V RMS

To sum it up, Qudelix-5k offers a total of four DAC/AMP modes, and the users can trade-off the output power and battery time.