ECdesigns PowerDAC-RX User manual

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PowerDAC-RX!
!
User Guide

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Introduction
The PowerDAC-RX is a discrete power multi-bit DA converter without -any- amplifiers or
buffer circuits in the signal path. PowerDAC-RX has integrated lossless volume control.!
Balanced programmable linear power-supply, bit shifts and resistor attenuator are used to
generate the output signal.!
The PowerDAC-RX is intended for driving amplifiers and headphones.!
Highlights
•Custom DAPI receiver offers high source immunity!
•Toslink input!
•Bit-perfect tester built-in!
•Optional IR remote control!
•Local volume control keys integrated in display, press left/right!
•Connect to (pre)amplifiers using RCA!
•Connect to headphones with optional RCA to 3.5mm Headphones adapter cable!
•Firmware upgradable!

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Block diagram

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Batteries are used in the examples above to simplify the theory of operation, in reality these are
programmable linear power supplies as shown in block diagram above. Each set of switches (top, bottom)
represents a separate divider. We have: two batteries, an RCA output (VU meter), two equal resistors R,
and two electronic switches. Batteries are a short circuit for AC signals (audio signals). The resistor sets
attenuate the battery voltage in order to generate an analogue output signal.
A/D) Upper switches on maximum plus, lower switches on maximum minus, currents cancel, zero output
voltage.
B/E) Only upper or lower switches on maximum, currents partially cancel, attenuated output voltage.
C/F) All switches on maximum and same polarity, all currents add, maximum output voltage.
In all 3 cases we have four resistors with value R in parallel and batteries are short circuit for AC. So
output impedance in all examples remains constant 0.25R regardless of switch position.
By changing the electronic switch settings we can have no voltage, half positive, full positive, half negative
and full negative output voltage.
In the practical converter we also have two converters for generating the output signal (matrix system).
This ensures that only the lowest bits have to change state around the zero crossing as each converter
starts at minimum or maximum and progresses up or down in small steps, not in the middle like with most
multi-bit DACs.
The lower bits are switched with R4R, the upper bits of each converter are split up in sub bits (fractal
system). This helps to further lower output impedance to 50 Ohms with given switch limitations, increase
accuracy and minimise glitches.
The end result is an accurate and clean multi-bit power DA converter with low enough output impedance
to directly drive the outputs. This way all lossy analogue circuits and related unavoidable degrading,
typically required for conventional DACs can be avoided.

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PowerDAC-RX
PAGE 1
DAC type
4 x 20 bit Fractal-7 matrix, discrete, switch & resistor-based multi-bit power converters
Digital input
1 x Toslink 16/24 bit: 44.1 kHz / 48 kHz / 88.2 kHz / 96 kHz / 176.4 kHz / 192 kHz
Power Supply
Programmable internal linear power supply!
Standard 230V (option: 115V)
Power Consumption
Approx. 2 Watts
Output impedance
50 Ohms regardless of volume setting
Volume control
Volume is controlled by a combination of supply voltage programming (1.5dB steps) and
bit shifting (6dB steps). This way we can realise lossless volume control with no extra
components in the signal path and with 36dB range.!
This integrated volume control enables us to directly drive headphones and power
amps / buffers without the need for an always lossy pre amp or attenuator.
Output voltage
28 mV rms … 1.77 V rms Output voltage. Output can be fixed to 1.77 V rms with jumper
setting
Output
2 x RCA output, headphones can be connected through optional RCA to jack adapter
cable RCA35.
LED display
Volume 0 … 24, -= stand-by, P= bit perfect test passed.
PowerDAC-RX and
headphones
The PowerDAC-RX makes it possible to directly drive many headphones (32 Ohm and up)
without any analogue amplifier or buffer in the signal path. In other words the headphones
are directly driven by a balanced power supply, a number of digital on / offswitches and a
resistor array. This eliminates all distortion and degrading that is typically introduced by
conventional headphone amplifiers. With this distortion and degrading completely
removed it is obvious that we end up with a much cleaner signal that lets one listen much
deeper into the recording and offers a more realistic representation of the recorded music.
Bandwidth
Theoretically 100 MHz (based on switching speed)
Distortion
< 0.001% (0dB)
Technical specifications

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PowerDAC-RX
PAGE 2
POWER
Output Voltage
shifts
attenuation in dB
-
0
28 mV rms
4
-36 dB
1
33 mV rms
4
-34.5 dB
2
39 mV rms
4
-33.dB
3
47 mV rms
4
-31.5 dB
4
56 mV rms
3
-30 dB
5
66 mV rms
3
-28.5 dB
6
79 mV rms
3
-27 dB
7
93 mV rms
3
-25.5 dB
8
111 mV rms
2
-24 dB
9
132 mV rms
2
-22.5 dB
10
157 mV rms
2
-21 dB
11
187 mV rms
2
-19.5 dB
12
222 mV rms
1
-18 dB
13
264 mV rms
1
-16.5 dB
14
314 mV rms
1
-15 dB
15
371 mV rms
1
-13.5 dB
16
445 mV rms
0
-12 dB
17
527 mV rms
0
-10.5 dB
18
626 mV rms
0
-9 dB
19
746 mV rms
0
-7.5 dB
20
884 mV rms
0
-6 dB
21
1.05 V rms
0
-4.5 dB
22
1.25 V rms
0
-3 dB
23
1.48 V rms
0
-1.5 dB
24
1.77 Vrms
0
0 dB
Technical specifications

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PowerDAC-RX
PAGE 3
Integrated bit-
perfect tester
With muting on (display:"-") and using supplied bit-perfect test wav files, the display
will show "P" when test wav file is received by the PowerDAC-RX without
modification.
Auto-mute
When no Toslink data is received the PowerDAC-RX will switch to muting after
about 15 minutes. When Toslink data is received again the previous volume setting
will be restored.
DAPI firmware
update!
The DAPI firmware can be updated using the USB socket and jumper setting
positions for firmware update.
Dimensions
Width: 30cm, Height: 5cm, depth: 23cm
Weight
1.5 kg
Technical specifications

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Bit-perfect test
It is essential to test if the Toslink source that is connected to the PowerDAC-RX is setup to pass music without
any alterations. Alterations of original music data could cause serious SQ degradation !!
WHEN SOURCE IS NOT BIT-PERFECT PLAYBACK THROUGH POWERDAC AND OTHER DACS WILL NOT
REPRODUCE THE MUSIC AS INTENDED !!
Alteration to original (CD) recordings could have numerous causes e.g.!
•Software volume control in streamer/player/pc music application!
•Equalisation in streamer/player/pc music application!
•Sample-rate conversion in streamer/player/pc music application!
•Compression in streamer/player/pc music application!
•DSP alterations in streamer/player/pc music application!
•Re-clocker devices in digital signal path to PowerDAC-RX!
•Isolators in digital signal path to PowerDAC-RX!
•Other devices in digital signal path to PowerDAC-RX!
•Use of MQA (test) files converted to MQA!
•Streaming services you can’t test but they might do any of the above.!
•Other ?!
To make sure that music data is received by the PowerDAC-RX without alterations you can use the built-in !
bit-perfect tester in the PowerDAC-RX**.!
For this we have 4 wav test files (44.1kHz / 48kHz / 88.2kHz / 96kHz*) that can be played on your !
source (streamer/player/pc music application) to check if the music data arrives in the PowerDAC-RX !
without alteration.!
This can only be tested with the PowerDAC-RX in the muting volume setting (“-“ on display).
You have to wait until the streaming on PowerDAC-RX stops (the decimal point “.” is off)
before (re)trying (next) track !!
Make sure that sample rate is correctly set before playback (in streamer/player/pc music application).!
Now play the track, when track play is finished a “P” should be displayed, if not then playback is NOT bit-perfect.!
The “P” will become “-“ after stream stops (“.” is off).!
You will have to re-run bit-perfect test if anything (any setting) is changed in your steamer/player/pc music
application.!
Download and unzip the bit-perfect test wav files using this link: pd-bitperfect-wav-files.zip!

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Jumper settings
Disconnect the mains power cable from the PowerDAC-RX !
In order to access the jumpers, remove the PowerDAC-RX TOP cover by removing 6 x 2mm hex bolts.!
Carefully remove or place jumpers using tweezers.!
When replacing the top cover, make sure side, rear and front panels lock into the top cover slots correctly before
tightening the 6 hex bolts.!

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Firmware update
To update the PowerDAC-RX firmware you need to download the STM32CubeProgrammer.!
You need to ACCEPT Licence Agreement (click button) and on the next screen you need to fill-in your E-mail
address to be able to download STM Cube programmer (you need to use confirm via email sent to you before
you can download the STM Cube-programmer).!
The email sent to you contains the Download now button to start the download.!
Goto link below to download the STM Cube programmer (Win/Lin/Mac):!
https://www.st.com/en/development-tools/stm32cubeprog.html#get-software!
Download and install STM32CubeProgrammer!
Disconnect mains cable from the PowerDAC-RX
Remove top cover by removing 6 hex screws on top in order to gain access to jumpers and USB socket.!
Use tweezers to set the red jumpers.!
Use tweezers to set the red jumpers on rear of PowerDAC-RX !
to PROGRAM configuration (see Jumper settings on previous page).!
Download and unzip latest pdrs-firmware.zip!
Now connect a USB cable from the PowerDAC-RX to your computer and start the STM32CubeProgrammer.!

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Screenshots here from
STM32CubeProgrammer
On the right hand side of the screen you should see:!
Port: USB1, if not then try the refresh button on the right
side of the Port dropdown button.!
If not working check jumper settings and USB cable
connection.!
Now press the Connect button.!
Then use the Open file button to load the firmware file.!
Click the Download button to load firmware file in the
PowerDAC-RX.!
After message: File download complete!
Press the OK button on message window.!
Finally click on the Disconnect button to finish session.!
You can then close the STM32CubeProgrammer.!
Remove the USB cable between PowerDAC-RX and PC.!
Set jumpers to the normal positions.!
After power-up PowerDAC-RX the new firmware is used.

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Alternate firmware update
If you don't want to register and download STM32CubeProgrammer then you can also use the dfu-util
command-line utility to download new firmware into the PowerDAC-RX.!
For this you will have to use the command-line to update firmware.!
Download dfu-util here: http://dfu-util.sourceforge.net/releases/dfu-util-0.11-binaries.tar.xz!
After unpacking open shell/command window and change directory to “dfu-util-0.11-binaries“!
Depending on your operating system change directory to the directory containing the dfu-util executable for
your operating system.!
Disconnect mains cable from the PowerDAC-BX
Remove top cover by removing 6 hex screws on top in order to gain access to jumpers and USB socket.!
Use tweezers to set the red jumpers.!
to PROGRAM configuration (see Jumper settings on page 9).!
Now connect a USB cable from the PowerDAC-RX to your computer.!
Now copy the firmware file (see page 10) e.g. PDRS140.bin into the same directory containing the dfu-util
executable.!
From this directory execute:$dfu-util -a 0 --dfuse-address 0x08000000 -D PDRS140.bin!
If this completes without errors (File downloaded successfully) your firmware should be updated.!
Disconnect the USB cable from PowerDAC-RX and set jumpers back to their original position.
Close the housing !!
After power-up, the new firmware is used.!

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IR Remote Control
The IR Remote Control is an optional product that can be!
used with the PowerDAC-RX.!
The IR Remote Control can be used to:!
•Increase volume!
•Decrease volume!
•Mute/Un-mute!
The IR Remote Control can be recharged with the !
included USB mini cable.!
Connect to a 5V source like PC or 5V USB charger to charge.!

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UT96
The UT96 is an optional USB to Toslink converter that!
can be used with the PowerDAC-RX.!
It supports USB full-speed:!
44.1kHz / 48kHz / 88.2kHz / 96kHz!
Use standard USB cable to connect to PC/Host/Streamer.!
UT192 (Optical + ElectroTos output)
The UT192 is an optional high-speed USB to Toslink converter that!
can be used with the PowerDAC-RX or other Toslink DACs.!
It supports USB high-speed:!
44.1kHz / 48kHz / 88.2kHz / 96kHz / 176.4kHz / 192kHz !
The UT192 is based on the XMOS processor.!
Use high-speed USB cable to connect to PC/Host/Streamer.!
The UT192 has both optical Toslink output + ElectroTos output.!
We found that using highest sample rates some optical Toslink cables would not work.!
Depending on the quality of the Toslink cable, optical reflections can prevent reliable (bit-perfect) output !!
Therefore we also fitted the UT192 with an ElectroTos output.!
ElectroTos (using standard S/PDIF output) uses an electrical cable with a LED on the other end.!
This eliminates optical reflections but can still use standard Toslink input.!
So the UT192 can also be used with other DACs that use Toslink.!
A 1 mtr. ElectroTos cable ET100 is included with UT192.!
An 2 mtr. ElectroTos cable ET200 option is also available in webshop.!
An 4 mtr. ElectroTos cable ET400 option is also available in webshop.!

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ElectroTos
“New” digital audio interface!
Backwards compatible with Toslink interface and S/PDIF protocol. Our “new” electro-optical digital audio
interface eliminates -unwanted- jitter in digital audio source, digital audio interlink, and all DAC circuits even
when significant crosstalk is present.!
This new digital audio interface maintains low noise and low jitter. It can be used to improve the sound quality of
all existing Toslink DACs. The transmitter side (digital audio source) is connected to a coaxial cable through a
RCA connector. At the end of the coaxial cable there is an optical connector compatible with the Toslink input
on the DAC. So this is a combination of an electrical interface (low jitter) and an optical interface (low noise,
elimination of ground loops). The required signal level is higher compared to existing coaxial S/PDIF interlinks,
so a suitable translator or source are required. We offer a USB to ElectroTos translator that outputs ElectroTos.
ElectroTos can operate with standard S/PDIF protocol (compatible with existing DACs)!
This measurement compares a high quality Toslink
interlink (top) and the “new” ElectroTos interlink
(bottom). The signal is measured inside the DAC at the
Toslink optical receiver chip output. sample rate equals
96 KHz, standard S/PDIF protocol.!
The Toslink optical fibre interlink causes time distortion
(jitter). This is visible as unsharp and not clearly
defined vertical green lines (X-shape on this picture).
This Toslink jitter problem is well known.!
The new ElectroTos interlink offers significantly lower
time distortion (jitter). This is visible as sharp, clearly
defined vertical lines (X-shape in this picture). Good
coaxial S/PDIF interfaces can offer similar low jitter, but
fail to block RF ground loop noise and very large
bandwidth noise in general.!
ElectroTos offers low jitter, blocks RF ground loop
noise and offers a clean, band-limited output signal.!
Below you can see two oscilloscope screen captures

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Volume control and Inputs
The DAPI controller has 4 S/PDIF inputs, so why not use all of them ?!
The whole point of the PowerDAC is to achieve Digital to Analog conversion with minimal noise input and the
lowest possible distortion without -any- amplifiers or buffer circuits in the signal path.!
We initially wanted to use all of the 4 S/PDIF inputs but by doing so we would let up-to 4 S/PDIF sources
into the DAPI controller simultaneously. Now the not used inputs that contain a live S/PDIF stream will inject
noise into the DAPI board even if this input is not selected.!
The only solution to use multiple S/PDIF inputs without causing extra noise injection into the PowerDAC is to
move them outside the PowerDAC.!
One possible solution is using an external input switch like the one below.!
It has 4 S/PDIF inputs and includes a remote control for selecting the active input.!
Digital Audio-Switch!
!
The PowerDAC Volume control consists of data bit-shifts combined with fixed voltage levels.!
The smallest volume change we can hear is about 3 dB, when the received audio data is shifted by one bit,
this corresponds to a 6 dB attenuation per shift.!
We use a combination of fixed voltages + bit shifts (max 4) to change the volume.!
Bit shifts only drop bits from the 4 least significant bits.!
We use 9 voltages in combination with up to 4 bit shifts in the PowerDAC-RX giving a total of 25, 1.5 dB
volume steps.!
When using the PowerDAC i.c.w. an external (pre)amplifier performance is degraded as any active device in
the audio path will degrade performance !!
By setting a jumper on the PowerDAC-RX you can set fixed output without using any bit shifts.!
!

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piCorePlayer
If you are looking for simple music player for stand-alone or even multi-room to use with the PowerDAC-RX
checkout piCorePlayer.!
When run from an RPI4 you could connect your music to the RPI4 directly by USB or to NAS via network.!
By using the JustBoom Digi HAT or the HifiBerry Digi(+) HAT you can connect the PowerDAC-RX !
using a Toslink cable.!
It supports 44.1kHz / 48kHz / 88.2kHz / 96kHz / 176.4kHz / 192kHz.!
Be sure to set Audio Volume Control to fixed at 100%, set Audio Crossfade to No, Volume gain to None.!
Then install “Material Skin” in LMS and choose in LMS pages under “Web Interface” and you will have a very
nice user interface using any browser on any PC in your network.!
Use Deezer and Tidal.!
Through plugins you can also use Spotify and Qobuz!
For more info see:!
https://www.picoreplayer.org/landingzone_option3.html!

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Software that is able to produce bit perfect output to PowerDAC:
Note: most playback software on MacOS does not follow sample-rate settings of track !!
•JRiver Media Center 31 (default settings with volume set to 100% on MacOS) *follows sample-rate on MacOS !!
•Foobar (with correct settings on MacOS)!
•Swinsian (with volume push to max after program start on MacOS) *follows sample-rate on MacOS !!
•VLC (with volume set to 100% on MacOS)!
•VOX (with volume set to max and eq offon MacOS)!
•Musique (default settings with volume set to 100% on MacOS)!
•Music-Player Lite (default settings with volume set to 100% on MacOS)!
•Amara Luxe (settings: buffer to 32 samples, exclusive access on, volume set to 100%, on MacOS) * follows sample-rate on MacOS
but fails occasionally ?!
•Audirvana Origin (default settings with volume set to 100% on MacOS)!
•Korg AudioGate Lite 44/48(with volume set to 100% and buffer size to 256 samples on MacOS) * follows sample-rate on MacOS!
If you use playback software with our PowerDACs and you have successfully run bit-perfect test (44.1, 48,
88.2 and 96) please let us know so we can update bit-perfect player software here.!

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Hardware players that are able to produce bit perfect output to PowerDAC:
•piCore player (with correct settings and volume 100% on RPI)!
•
If you use playback hardware with our PowerDACs and you have successfully run bit-perfect test (44.1, 48,
88.2 and 96) please let us know so we can update bit-perfect player hardware here.!