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Audio-GD - R 28 TCXO - Balanced R2R Ladder FPGA DAC / Pre / Headphone Amplifier (DSD, DxD, Amanero USB)

€ 1.239
€ 1.024 ohne MwSt
TCXO Upgrade
Audio-GD - Remote Control (IR) AluminiumInformation
Power cable (Default C13 EURO)
Singxer F1 USB (Replace Amanero) with installationInformation
Audio-GD - Digital SPDIF coax interlink BNC (1m)Information
Audio-GD - Digital SPDIF coax interlink RCA (1m)Information
Audio-GD - ACSS Analogue balanced interlink (mini-xlr)Information
Audio-GD - Analogue RCA interlink stereo pair (1m)Information
Audio-GD - Optical Digital Toslink Cable (1M)Information
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Audio-GD - R-28 - Discrete R2R TCXO Pre/Head-Amp (PCM & DSD/DxD Balanced DAC)

Balanced discrete R-2R digital analogue converter equipped with advanced high speed ladder correction including optimized FPGA FIFO buffering and re-clocking. All parts and components are selected based on excellent sonic and measurements performance. Components used are e.g. WIMA caps; DALE and Vishay resistors, KOA transistors and NOVER capacitors. The design (e.g. low noise power supplies; discrete analogue output stages) were being selected after many years of experience and practices and are considered to perform and provide finest sound quality. Up to date technology supporting high resolution including native DSD, DxD and hyper-modern inputs like Amanero USB and LVDS I2S inputs.

Unique R2R correction technology. Digital signal processing driven by high-speed FPGA supporting FIFO buffering and re-clocking. Software up-gradable design enables future new capabilities and improvements.


LATEST PRODUCT UPDATES

This product includes:

  • 23-07-2018: Latest v2 FPGA software updates
  • 28-03-2018: Latest R2R dac boards firmware release: Silent PCM sample rate switching
  • TCXO Upgrades


SUMMARY

Software up gradable design. Two high performance TCXOs to process different sampling rates 44,1kHz and 48kHz sampling range to eliminate jiter.

  • True balanced design
  • Headpone Super Single ended output
  • Digital DSP for optimal signal processing
  • 4 Groups DA-8 R-2R Modules
  • Internal OCC wires & low-jitter TCXO clocks applied
  • Discrete analogue output stages
  • DC coupled design (No capacitors in signal path)
  • Non- feedback ACSS analogue output control
  • High-grade matched transistors per channel
  • USB Amanero Combo384 interface
  • High Res support: DSD64 - DSD512 & DxD

SOUND CHARACTERISTICS

R-28 is characterized by its coherent, transparent and natural sound. Striking is the spatial sound image. Rich in detail and strong authority. You'll forget that you're listening to a digital source.


DIGITAL INPUTS
  • Input 1: HDMI-IIS
  • Input 2: USB
  • Input 3: Optical SPDIF
  • Input 4: RCA Coaxial SPDIF
ANALOGUE INPUTS
  • Input 5: RCA Single Ended
  • Input 6: XLR Balanced

OUTPUTS
  • ACSS balanced
  • XLR balanced
  • RCA single ended

Headphone Super Single Ended Output

The single ended heapdhone (6.3mm jack output) headphone output supports super single ended output. By selecting the "S" output in thte menu you can activate the single ended output to fully power and drive the headphone as if it was a balance output.


HIGH PRECISION VOLUME CONTROL

Volume control consist of relay-controlled attenuators. Fully-independent, fully-balanced stereo volume controls. The volume controls feature high-precision 0.05% tolerance film resistors, gold contact relays, and fully buffered inputs and outputs.There 4 channels volume boards built in the unit for the balance volume control. They are control by digital signal but applied relaies control the resistors in analog area


 

R-2R DESIGN

The R-2R DAC has become popular and affordable. From DIY kits and completely up to of the shelf high-end products.
In the lower end DIY market, the R-2R design is often based on old technology; designed long time ago by MSB, often includes basic R2R ladder design only and not include the wonderful correction design of the modern MSB technology. Previous less good designs used data shift registers logic chips in serial mode to convert the data to an analog signal. The stubborn R2R issues cannot be avoided this way and performance is almost entirely depending on the accuracy of the ladder resistors. 

In the High-End of the shelf (finished products) market, the R2R design is usually much more complex when outstanding performance is offered. A basic R2R ladder is simply not sufficient to achieve the desired sound quality. Some manufacturers are using shift registers design to realize ladder compensation. A less complex, unfortunately also a less performing design based on traditional logic chips working in serial mode.
A far better design switches resistors in parallel mode; an ultra-fast FPGA chip controls and corrects the R2R ladder. The parallel design mode controls every bit respectively and therefore achieve unprecedented performance. (In parallel mode only 1 clock cycle is needed to output all data; serial design mode needs at minimum 8 up to 24 clock cycles) The parallel design is particularly complex, however when it is done properly it can correct every bit of the ladder. (Photo below shows a FPGA design with R2R ladder). With incredible speed and accuracy the R-28 will correct the unavoidable imperfections of the basic R2R ladder caused by tolerance of resistors; avoid glitches at ultra-high speed to deliver unrivaled musical performance.

 

agd r2r7 mh

TOLERANCE OF RESISTORS IN LADDER

Some manufactures claim to achieve good performance becuase they use lowest tolerance ladder resistors. The following calculation example will cover this. At 16 bit the tolerance of 1/66536, 0.1% (1/1000) it is by far not enough to achieve decent performance. Even using resistors with 0.01% (1/10000) tolerance, lowest tolerance available today,cannot deliver the desired performance This is just 16 bit, imagine a 24 calculation! To process 24 bit resolution it would require resistors with a tolerance of 0.00001%. This is purely theoretical; if this tolerance would exist the discreteness of the switch logic chips will already have too much internal impedance and will shake-up such design.The tolerance of the resistor will never solve Imperfections of a ladder.

The solution lies in the correction the ladder and not only depend on the tolerance of resistors. It’s a combination of both: Ultra-low tolerance resistors controlled by a correction technology using very high speed with parallel FPGA processing.

 

PROS AND CONS OF DISCRETE R-2R LADDER DAC

Advantages

  1. R-2R will not convert the clock signal into the output signal.
  2. R-2R is less sensitive to jitter
  3. The output signal is more accurate with R-2R

Weaknesses:

  1. Modern Delta-Sigma chips offer exceptional THD; R-2R offers satisfactory THD results. 
  2. Accuracy and glitches of the ladder resistors require complex technology to enhance 

 

ULTRA FAST SIGNAL PROCESSING

FPGA stands for Programmable Array Logic. Nowadays the FPGA is widely adopted in audio devices. The internal hardware design is fully controlled by complex software. A huge advantage is the fact the software in the FPGA can easily be upgraded offering new capabilities or improve the performance of the device without replacing any hardware. Flexible and future proof design.

R-28 FPGA responsibilities:
  1. High performance SPDIF interface, replacing traditional less good performing SPDIF interface chips like DIR9001, WM8805 or AK411X,etc.
  2. Full re-clocking process with FIFO design applicable on all inputs. This way the output data keeps fully synchronized with the clock signal to reject any jitter.
  3. Built in 2X, 4X and 8X oversampling and digital filters and on top of this 4 different true NOS (only analog 6dB filtering) modes. To completely configure the sound according to your taste.

 

ANALOGUE OUTPUT STAGES

The analog output stages are as important, they have a tremendous influence on the final sound quality. After d/a conversion by the R2R D/A modules the analogue signal is transported by fully discrete matched-transistor output stages; DC-coupled design with first class through-hole components. No SMD components are applied in the analogue section. The high speed unique ACSS ((Audio-gd Current Signal System) output stages are non-feedback and current driven. Unique performance because almost all other designs need to convert the signal multiple times from and to current and/or voltage, resulting in less detailed and less transparent sound-stage.
The output buffers are single ended FET; two stages in parallel to reach very low output impedance. All output stages are in pure class A without (negative) feedback to achieve purest and a real live sound reproduction.
The 4 OPA op-amp's are DC servos, this way no coupling-capacitors are needed and DC output is automatically biased. Resulting in a strikingly neutral sound.


R2R710.jpg

POWER SUPPLIES

The DAC consist of 3 tuned low noise, low flux leakage, R-cores transformers. In total 130W power to supply all digital parts and the left and right analog boards. The DC power is distributed over 19 separate power regulators. All are pure class A low noise shunts; fed by 3 groups linear power supplies. Resulting in ultra-high speed and clean power for all individual parts.


DIGITAL CONFIGURATION GUIDE
DSP configuration for R2R DAC's
 
 
Release Date July 2018
 
 
 
Firmware release: R7V2(X-X)
 
 
 
 
MODEL Jumper Setting Note
Oversampling Mode (OS) Bypass OFF Oversampling + digital passband filter
Non Oversampling mode (NOS) Bypass ON NON Oversampling + 6dB analogue filtering
       
Generic Settings
Jumper
Default
 Note
Input 4 clock regeneration
S0
OFF
Default is OFF. If the sound had issue, change the setting
Input 5 clock regeneration
S1
OFF
Default is OFF. If the sound had issue, change the setting
Input 6 clock regeneration
S2
OFF
Default is OFF. If the sound had issue, change the setting
PLL
PLLEN
OFF
 
Dithering
Dith
OFF
 
 
 
 
 
Oversampling (OS, digital passband filter)
Jumper
Jumper
BYPASS JUMPER OFF 
Oversampling
IPS0
IPS1
Default both OFF
8x
OFF
OFF
 
4x
ON
OFF
 
2x
OFF
ON
 
1x
ON
ON
 
 
 
 
 
NOS (Pure NOS, analogue 6dB Filter)
Jumper
Jumper
BYPASS JUMPER ON
NOS MODE
ATT0
ATT1
Default both OFF 
NOS 3
OFF
OFF
 
NOS 3
ON
OFF
 
NOS 2
OFF
ON
 
NOS 1
ON
ON
 
 
 
 
 

USB SUPPORT

Download USB Amanero drivers for Windows 10
Download USB Amanero drivers for Windows 7 & 8

No drivers required for Linux and/or Mac OS
OSX 10.6+ and Linux with UAC2 compliant kernel
Microsoft Windows: KS/Wasapi/WDM/ASIO


 

Hersteller-URL: http://www.audio-gd.com/R2R/R28/R28EN.htm
Gewicht: 7 kg
Breite: 360 MM
Länge: 360 MM
Höhe: 85 MM
Hersteller: Audio-GDAudio-GD

Spezifikationen

R-2R Discrete Ladder(s)
>110DB
2.5V (RCA) 5V (XLR) 2MA+2MA (ACSS)
0.5 Vp-p
19 dBm
USB / I2S 44.1kHz - 384kHz /32Bit & DSD64-DSD512.| Coaxial: 44.1kHz - 192kHz /24Bit Optical: 44.1kHz - 192kHz /24Bit
1.0, 1.1, 2.0 & 3.0
Windows, iOS, Linux
> 120dB
0.05dB
7
19W Version 1: 100-120V AC 50/60 Hz Version 2: 220-240V AC 50/60 Hz
360*360*85mm
Remote Control
USB Cable
IEC Power Cord

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