Allo Mini BOSS pHAT - Pi Zero "Master" DAC
There are many DACs for Raspberry Pi Zero. Most of them low-priced, carbon copy of datasheet, slave DACs.
Allo decided to do something different. . . . introducing the first Master DAC for the Pi Zero, based on PCM5122 with many improvements over the standard circuit!
The Raspberry Pi has one major problem with audio - The clocks coming from CPU can only output one frequency clock perfectly, resulting in problems such as jitter with audio files sampled at 44Khz.
So what's the solution? Enter the master mode for i2s. Instead of the Raspberry Pi giving the clock on the line, the Mini BOSS DAC itself sends the clocks and the Raspberry Pi sends the data!
Our Mini BOSS DAC is unique; First we separate the power on 3 channels and filter it: one for the digital side, the second for analog and third for the clocks themselves. Then we take the filtered power and use a second filter (LDOs) to further quiet the noise. Note that we use some of the best LDOs on the market (LT3042 from Linear). In addition, we use Japanese oscillators from NDK for a very low jitter clock - almost as good as famous Crystek.
Finally, on the analog stage the Mini BOSS DAC uses a film capacitor (not ceramic) for a quiet DC to feed the TI IC (ceramic exhibits some piezo distortion, not what you want in analog stage). Not happy with this, we have added a supercapacitor for an extra kick when analog stage is asking (like deep bass).
What we have achieved, in our opinion, is the best analog implementation of the PCM5122 on the market, while at same time correcting the clock problem from RPI.
The Mini BOSS DAC is a very solid implementation of the PCM IC that will give you the greatest bang for your buck. It will sound great no matter what you throw at it - this was our goal and promise to you.