RPi-DAC-RCA - Be more flexible - enjoy better sound quality

• works with latest Raspbian and Volumio distro
• 1x PCM5102 - 24bit DAC [1], up to 384KHz
• cost-effective alternative to HifiBerry [2], additional features
• DAC power decoupled from Raspberry Pi (improved audio quality due to very-low-noise LDO)
• power Raspberry Pi from SPS and all your other extensions (capable to provide 2A current)
• change any time from RPi-DAC-RCA to higher quality RPi-DAC just by changing the HW module
• even possible to stack RPi-DAC-RCA as well as RPi-DAC, to operate both in parallel (two separated outputs)
• start smart and cheap and upgrade any time to better audio quality, don't let block your RPi extension header P1

Durio Sound

It is now Durio Sound

Please see: It's now Durio Sound

Listening experience

A subjective listening comparison results in:
The HifiBerry-like DAC is acceptable, quite OK. I can hear clearly the difference when listening to the RPi-DAC (better).
The RPi-DAC-RCA (or HifiBerry) sounds a bit flat, the bass is power-less and the treble is not really clear, I miss the colors in the sound.
The sound seems to be OK (free of noise) but it is a bit flat and power-less.
I prefer listening to RPi-DAC (even Single Stereo version provides a much better sound).
(You can run both in parallel for your own comparison, you can stack both DACs.)

Overview

The P1 extension header remains completely free.

Stack vertically, RPi-DAC-RCA is below the RPi.

You can use any other module, even possible to run different modules in parallel.

Use options in order to improve sound quality (e.g. very-low-noise LDO or SPS).

Remark: the P5 connector is soldered from the buttom side (male). The RPi-DAC-RCA module is placed under the RPi. It might be possible to change the orientation so that RPi-DAC-RCA sits on top of RPi.

Blockdiagram

The Standard version powers the DAC from RPi via 3.3V from RPi LDO, still using USB power supply

Option A: has a dedicated, very-low-noise LDO for the DAC (better sound quality)

Option B: provides a Switched Power Supply (SPS) which powers RPi and all your extentions (max. 2A)

The SPS option takes just direct AC transformer or any other input and can provide up to 2A current (e.g. for your extension boards), no USB power supply

You can upgrade the board any time or change to higher quality RPi-DAC without any system changes

Option AB: Power Supply for RPi and extension boards, LDO for decoupled DAC and SPS, no USB power supply

Option C: all - just instead of 3.5mm stereo plug two RCA connectors and LDO, SPS

Option D: use as Power Supply for RPi and extension boards, no DAC, no LDO, can be soldered anytime later

Schematics

The +3.3V is derived from the +5V from RPi (Option A) or from SPS (Option B) with an AC/DC wide-voltage-range input

The soft-mute feature (XSMT) is used in order to watch the main power supply rail.

The DAC PCM5102 runs in PLL mode.

The output signal is provided on a 3.5mm stereo jack or dedicated RCA connectors.

Remark: even with SPS soldered, it is possible to let it unpowered (no AC) and to power the RPi still via USB power supply. A diode allows to use USB power supply still. BUT: never use both active at the same time.

Rasbian Linux Update

If you think anything necessary to change on your running system (Rasbian, Volumio) - NO!
Just change the HW module, use still the same driver (RPi-DAC or HifiBerry) and setup - and it works.
You can change anytime from HifiBerry to RPi-DAC-RCA without changes on your system.
You can upgrade (solder additional parts) any time later on Standard RPi-DAC-RCA, e.g. to use the SPS and any AC/DC input, having 1A current left for your extensions.

Rasbian /etc/modules

The latest Rasbian installed on SD card you should put the following settings in your file /etc/modules:

			##snd-bcm2835
			snd_soc_core
			snd_soc_bcm2708_i2s
			bcm2708_dmaengine
			snd_soc_pcm1794a
			snd_soc_rpi_dac
				

So, you can run the RPi-DAC-RCA even with the RPi-DAC drivers and change anytime to the RPi-DAC later without any modifications.

If you have installed mplayer, e.g. via
  sudo apt-get install mplayer
you can play and test directly on command line, e.g. via:
  mplayer http://80.237.158.40/radio-brocken-128.mp3

Design files and docs

RPi-DAC-RCA_overview.pdf (109K)

BOM_RPi-DAC-RCA.pdf (79K)

RPi-DAC-RCA_schematics.pdf (140K)

RPi-DAC-RCA_parts.pdf (299K)

UltraDAC_RPi_RCA.zip (35K) ExpressPCB file (ZIP)

RPi-DAC-RCA_booklet.pdf (35K) Shipment booklet

System Configuration

You can use almost all other RPi-DAC, T-DAC modules, even stacking with RPi-DAC is possible.

Exception: the RN52 Bluetooth module does not work directly on DAC PCM5102A, just on RPi-DAC with PCM1794A. You can use Bluetooth via RPi-DAC-SPDIF or RPi-DAC-FPGA module (with modified FPGA project).

So, you have the option to convert RPi-DAC-RCA into:

• an USB Sound Card with XMOS eval
• an USB Sound Card with RPi-DAC-IF and XMOS
• SPDIF/TOSLINK Sound Card with RPi-DAC-SPDIF or RPi-DAC-IF
• Bluetooth smartphone audio player via RPi-DAC-IF or RPi-DAC-FPGA with RN52
• Cost-effective USB Sound Card with STMF4Discovery

Almost all modules can accept AC and have on-board rectifiers. Some boards can be powered via DC direct connector without wiring (e.g. RPi).

Pictures

References

[1] see detailed circuit datasheets of original manufacturers

[2] http://www.hifiberry.com

[3] Overview (PDF)