Audio-GD – R1 NOS – Balanced R2R DAC
USED UNIT, 100% OK, Mint Condition, 1 year warranty
The Audio-GD R1 NOS R2R DAC is a fully discrete, balanced DAC designed for pure, natural sound reproduction. Using a true R2R ladder architecture in NOS (Non-Oversampling) mode, it delivers an organic, analog-like presentation with exceptional timing and tonal accuracy. A robust linear power supply and fully balanced signal path ensure low noise, high dynamics, and outstanding musicality—ideal for listeners who value realism and refinement over digital processing.
The analogue outpus are RCA single ended; XLR balanced and propriatory ACSS balanced current outputs.
Remote Control included.
| Brand: Audio-GD |
| Product Type: Digital Analogue Converters (DAC) |
| Audio-GD Color: Black |
Audio-GD R1 R2R NOS DAC
Some people love the sound of the pure NOS mode , so we design the R-1 NOS that optimize the pure NOS mode , offer the pure musical sound .
The NOS design don’t need the main clock signal for working, that is the advantage of the NOS design to avoid the effect by the main clock’s jitter. In the R-1 NOS digital processor , we apply the zero delay technology that guarantee the data and clock exact synchronization for much reduce the jitter .
In the R-1 NOS design , we apply the galavanic isolator before the DA parts and analog parts , isolate the all digital inputs and the digital processor , that offer the better clean sound quality . 8 group built-in 24bit R-2R decoders and 4 native DSD decoders work with balanced mode, we apply the DA 7 modules that is an obvious upgrade than the last generation R-1 that apply the DA 8 modules. Using the latest designed discrete servo stabilized power supply to feed the digital circuits, the noise level is comparable to that of a battery, but without the dry and thin sound characteristics of it, and thus the product’s operating temperature is significantly lower than that of the previous model.
- Analog circuit are pure class-A regulated power supply to provide best sound quality
- In total8 groups PSU Class-A power supply in order to distribute the cleanest power to all components in the R1
- Sample Rate indication is displayed
- Remote Control
NOS (Non-Oversampling)
“NOS“ stands for “Non Oversampling“. In the 1970‘S, the first generation of the Compact Disc Player were released. By that time they all had Non Oversampling design.
Using NOS design, specs are ordinary because the limited signal bit depth affects THD and S/N. Despite the fact that quantization noise affects S/N, the R–1 NOS still achieves very low noise levels, much better than most tube amplifiers and turntables, and almost like a modern OS DAC.
To get better specs on paper, many designs use complex LC analog filter after the D/A conversion. But the LC filter usually does not have a flat response and the large phase shift it causes also affects sound quality considerably.
In 1980’s, oversampling and FIR filter were invented, and allowed improving sound quality compared to applying an LC filter. Good specs were obtained on paper, so this technology has been largely applied since that time.
However some people still like the sound of the “old” NOS design. They do not want the extra processing becuase without it does a better job preserving the original character of the sound. Do you trust your ears or do you need the best specifications?
If you are looking for great specifications, the NOS design is definitely not for you.
Multi-Functional Display
A new display type has been added to the R8 mk3. Both input and sample rate are now being displayed. (2 line multi-function display)
Firmware Update Port
On the back-panel of the unit an update port is available to quickly update the firmware using the USB Blaster (included).
FPGA Signal Processing
The internal hardware design is fully controlled by complex software. Software in the FPGA can easily be upgraded offering new capabilities or improve the performance of the device without replacing any hardware.
TECHNICAL SPECIFICATIONS
| Audio-GD R1 NOS | |
|---|---|
| DAC | R-2R NOS discrete ladder DAC |
| Inputs | USB HDMI (I2S) Coaxial RCA SPDIF |
| Outputs | Analogue RCA (Single Ended) Analogue XLR (Balanced) Analogue ACSS (Balanced) |
| Digital input sensitivity | 0.5V pp (75Ω Coaxial), 19dB on Toslink optics |
| Frequency Response | 20 to 20kHz |
| Output Level | 5V (XLR), 2.5V (RCA), 2 mA (ACSS) |
| Signal to noise ratio | 110dB |
| Output impedance | 10Ω (RCA) |
| USB and HDMI LVDS I2S | PCM 44.1kHz – 384kHz at 16-32bits |
| USB and HDMI DSD | DSD64 to DSD512, 32bit max, sample rates: 44.1kHz – 384kHz |
| Coaxial SPDIF input | 24bits max, sample rates: 44.1, 48, 88.2, 96,192kHz |
| USB | Windows (requires driver), MAC and Linux |
| Power Input | 230VAC / 115VAC |
| Power Consumption | 12Watt |
| Dimensions | 240 x 280 x 80mm |
| Weight | 5kg |
| Accessories | 1x USB cable 1x IEC power cable 1x Remote Control |
THE R-2R LADDER STORY
The R-2R DAC has become popular and was originally designed long time ago by MSB, and did not include the wonderful correction design of the modern MSB technology. In the High-End of the shelf (finished products) market, the R2R design is usually much more complex when outstanding performance is offered. Some manufacturers are using shift registers design to realize ladder compensation. A less complex, unfortunately also a less performing.
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.
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.
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. Versatile and future proof design.
- High performance SPDIF interface, replacing traditional less good performing SPDIF interface chips like DIR9001, WM8805 or AK411X,etc.
- 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.
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 compon ents 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. The listener will be presented a strikingly transparent and neutral sound.
ACSS – Current Amplification
Audio-GD has developed an advanced current-driven amplifier technique. Also known as ACSS, Audio-GD Current System Signal. This special technique ensures that the signal travels a much shorter path and that ensures a more transparent, faster and more neutral reproduction. A similar technique is used by, for example, KRELL. The Current Conveyor technology mostly components are the current mirror. The Current Conveyor technology isn’t a new technology, at 1966 , professor K.C. Smith and A.S.Sedra publish the concept “current mode analogue circuits “ .
