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Music Player with Terra-BerryDAC 2+ and Raspberry Pi

After the good result obtain with AK4137, on the DSC1 project, here using the Terra-BerryDAC 2+ module I am trying to assemble a compact Music Player with Hi-end performances.
The AK4137 allow the on the fly convertion from PCM to DSD so it is not necessary a good computer as player.

Main specifications of the Terra-BerryDAC2+ module

Model	Terra-BerryDAC2+
Main chips	DAC:AK4490EQ SRC:AK4137EQ OP-AMP:LME49720
I2S input	PCM ～768KHz, DSD(I2S DoP) ～11.2MHz
SRC output(DAC input)	PCM ：705.6KHz/32bit or 768KHz/32bit DSD(DoP):DSD11.2MHz
I2S input	RaspberryPi or Combo384
Output terminal	Unbalance, Balance
Power supply	+ 5V ± 5%
Current consumption	About 170 mA
Size	65 x 56 mm (RaspberryPi HAT compatible size)

It is possible power the Terra-BerryDAC2+ module with RaspberryPi but it is suggested use a separated power supply with linear regulator.

Built-in small crystal oscillator excellent in phase noise characteristics as master clock (45.1584 MHz for 44.1 KHz, 49.152 MHz for 48 KHz).

AK4137 + AK4490

DAC 2 AK 4490 and AK 4137

Connections and jump on of the Terra-BerryDAC2+ module

Raspberry Pi 3 model B

The Raspberry Pi 3 is the third-generation Raspberry Pi. It replaced the Raspberry Pi 2 Model B in February 2016.

Quad Core 1.2GHz Broadcom BCM2837 64bit CPU
1GB RAM
BCM43438 wireless LAN and Bluetooth Low Energy (BLE) on board
40-pin extended GPIO
4 USB 2 ports
4 Pole stereo output and composite video port
Full size HDMI
Upgraded switched Micro USB power source up to 2.5A

Volumio setting

To control this player you can use a normal smartphone or tablet of medium quality.
No Wi-Fi network is necessary because Volumio configure a Wi-Fi Hot-Spot with a private network.

Wi-Fi password volumio2

After downloading from the playstore open it and set the Playback Options with the following mode.

Power supply

To get the best audio performance probably is necessary use a linear power supply for both the sections of this module.
Only the Terra-BerryDAC 2+ have 2 power supply input, for the Raspberry Pi and DAC.
Remove the jump near to the power supply connector and add an external power supply.

The main problem now are the on-board DCDC used to create +5.5V, it could create noise.

I have used an external power supply with LT1083 linear regulator to increase teh performances

Tranformers output stage

The output trasformers has been selected after many test and also I have compared these with other models with much higher cost.
These have a turn ratio of 2:1+1, made with a permalloy core with a thickness of 0.16mm and a declared frequency response of 10Hz a 195 KHz-0.2dB.

I have got the outptut for the transformers directly on the AK4490 DAC output, the 4 large output capacitors help to create a simple and good contact.

Measurement

A very good result on measurement, the distortion is always less than 0.005% at 1.4Vrms (-6dB).
The max output voltage is 2Vrms at 0dB.