R2R-1 FPGA PCM/DSD DAC
Read the review at: https://headphone.guru/audio-gd-r2r-1-fpga-pcm-dsd-dac-done-right/
The R1 is an R2R full discrete DAC that uses 8 groups fully discrete R-2R DA modules to combine into a real balanced push/pull decoder. it also uses 4 group fully discrete real balanced DSD native decoders. It uses a fully discrete real balanced current transmition design. Jitter is kept ultra low by using dual ultra high frequency 90/98 MHz Accusilicon 318B femtosecond clocks to a provide synchronous clock for the whole unit without using a PLL up-frequency. The R1 works up to 32bit/384K with DSD512 asynchronous USB transfer thru the Amanero 384 FPGA synchronous clock. The entire whole digital circuit is built with single FPGA and 5 CPLD programmable chipsets to separate the different configured circuits to avoid interrupting the data stream process in parallel mode. The unit supports firmware updates future sound quality updates and all digital process mode settings are accessible by buttons on the front. In an R2R ladder DAC the unit switches resistors in parallel mode. An ultra-fast FPGA controls and corrects the R2R ladder. This parallel design mode controls every bit respectively and therefore achieves unprecedented performance. In parallel mode only 1 clock cycle is needed to output all the data so sonics are improved and the output is more analog like. After the D/A conversion by the R2R D/A modules the analog signal is transported by fully discrete matched-transistor output stages. The R1 DAC uses high quality low noise, low flux leakage, R-cores transformers to supply all digital parts and the left and right analog boards. There are in total 13 ultra-high speed and ultra-low noise power supplies built in and double stage PSU technologies are used to remove power supply voltage fluctuations.
Compare this DAC to anything we have heard under $2000.00-$2500.00.
R7HE MK2 State of the art Resistor Ladder DAC
FPGA controlled upgradable DAC w/regenerative power supply
The R7HE MK2 is a dual mono fully balanced Class A reference quality PCM/DSD DAC that is dramatically underpriced for its performance level. We have heard no DAC at near this price that presently competes with it. Most competitors are selling this level of quality for well over $10,000.00. Parts quality is world class.
Overview of this spectacular DAC
Fully discrete parts are used in a truly balanced current transmission design.
-4 sets of fully discrete and independent DSD hardware decoders.
-8 sets of fully discrete R-2R DA modules to form a two-channel balanced push-pull decoder.
-2 reference Accusilicon Femto clocks provide synchronization for the DAC. Tthey are applied to the playback of all data rates without PLL up-conversion.
-32bit / 384K asynchronous Amanero USB interface synchronized with the FPGA. USB and HDMI modules are equiped with galvanic isolators and fed by two groups of independent isolated power supplies, to avoid the mutual electrical contamination between USB and HDMI.
-The DAC uses the latest discrete servo stabilized power supply, whose performance is comparable to batteries after more than a year of calibration and optimization for each part of the circuit. The digital circuit uses new discrete servo stabilized power supplies, while the clock and the analog circuits are still powered by pure class-A power supplies to achieve the best sound, as determined during listening tests.
-The digital circuits of the whole DAC are comprised of 1 FPGA and 7 programmable chip sets which allow separating the different functional circuits and preventing interference.
-The FPGA operates in the parallel data processing mode even at the fastest data rate, and supports firmware upgrades to improve sound quality when new and better design ideas are eventually found and implemented.
-The input signal sampling rate is displayed.
-Support of an external 10MHz clock input (default is 50 ohms, can be customized to 75 ohms ).
-All digital mode settings can be changed on the front panel live.
-A firmware upgrade port is featured on the rear panel of the machine (no need to open to take off the cover to upgrade the firmware).
In order to completely eliminate the influence of jitter in the incoming signal, the R7 HE MK2 uses an asynchronous clocking process. First it reads and stores a considerable amount of signal data into a RAM buffer. It throws away the original clock of the signal source and directly uses the high-performance built-in Accusilicons Femto clock to clock the output from the RAM buffer. Since both data and clocksignals are handled by the FPGA the impact of transmission on jitter is neglectable. The jitter level is essentially the same as what is specified for the clocks. The DAC uses an asynchronous Amanero USB interface synchronized with the FPGA. It also has 4 sets of fully discrete and independent DSD hardware decoders.The power supply is servo controlled and virtually as quiet as a battery. The digital circuits are also servo controlled. It offers support for a 10MHz external digital clock.
Notice the upgrade port as well as the ability to add an outboard clock
R7 MK2 State of the art Resistor Ladder FPGA controlled upgradable DAC
Take the R7 HE MK2 top of the line DAC above and remove the internal HE power regenerator and you have the R7MK2.
The R7 MK2 is all discrete, dual mono, fully balanced and a Class A design. It is a reference quality R2R resistor Ladder FPGA controlled PCM/DSD DAC thatoffers close to state of the art performance and, we feel, the best DAC that you can buy for less than the $5k of the HE version. Technology and features are all the same as the HE above less the regenerator. Build and parts quality are superb. And, as the HE version, it is future upgradable with a software down load.
Inside shot of R7 MK2
R8 MK2 FPGA controlled R2R PCM/DSD DAC
Probably the best value of the Audio GD DAC's, the new 2021 R8 MK2 upgrades the original R8 from 2018 that received great press. A ladder DAC that is 90% as good as the best at a value price. It is even better when run thru an Audio GD preamp with ACSS buss
R-8 MK2 features:
Thanks to the fully programmable circuits of the R-8, the firmware is upgradable to improve the sonics.
Fully balanced XLR, RCA and ACSS (CAST) connectivity
The R-8 MK2 upgrade started at the beginning of 2020, which was followed by a year of continuous audition, software and hardware fine-tuning. Using the latest discrete servo stabilized power supply, whose performance is comparable to batteries after more than a year of calibration and optimization each part of the circuit was refined and optimized.
The new MK2 DAC uses a new discrete servo stabilized power supply while the analog circuits are still powered by pure class-A power supply to achieve the best sound, as determined during many long listening tests.
The improvement is quite obvious compared to the previous generation.
1. Fully discrete parts are used in a truly balanced current transmission design. Four sets of fully discrete and independent DSD hardware decoders. Eight sets of fully discrete R-2R DAC modules are used to form a two-channel balanced push-pull decoder.
The R8 MK2 uses the newly designed discrete servo stabilized power supply to feed the DAC circuits. In the new DAC the noise level is now 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. The analog circuit are still powered by a pure class-A regulated power supply for the best sonic results.
2. By listening to a turntable and studying its sound for a long time, Audio GD has successfully integrated an analog vinyl sound characteristic into the DAC. This tonal balance is optional and controlled through the front panel. This is a new feature.
3. Both the USB and HDMI inputs are equipped with opto isolators, and two sets of linear power supplies to separately supply power to the USB and HDMI modules before the isolators to prevent interference from signal sources. The USB input uses a two-way transmission isolator, which not only transmits IIS signals to the FPGA processor, but also receives the synchronous clock signal sent by the FPGA processor.
The USB interface itself is no longer equipped with clocks. The synchronous clock is applied to make the signal transmission more accurate and upgrade sound quality significantly over the older model. The HDMI module is now equipped with an independent isolator to improve the sound quality of the HDMI input.
4. The MK2 now has a display of the input signal sampling rate function.
5. The digital circuits of the whole DAC are comprised of 1 FPGA and 5 CPLDs (both programmable devices), which allow separating the different functional circuits and preventing interference. The FPGA operates using the parallel data processing mode. The parallel mode only needs one clock to transmit and process the 32-bit data of the left and right channels, which greatly improves the processing speed and is less affected by the stability of the clock.
6. Two superb Accusilicon Femto clocks provide synchronization for the whole unit, and they are applied to the playback of all data rates without PLL up-conversion. The clock management design of the new architecture makes the clock more stable, which brings a more transparent and detailed presentation.
7. DSD uses the built-in asynchronous clock to enhance timing, which obviously improves the clarity and dynamics of reproduction.
8. SPDIF supports DOP playback.
9. All digital mode settings can be changed on the front panel live.
10. A firmware upgrade port is on the rear panel so there is no need to open the cover to upgrade the firmware.
R28 (2022 version) Balanced preamp with resistor ladder DAC & 9.5wpc headphone amp
The R28 is a fully Fully Balanced solid state preamp with 9.5 watts per channel headphone amp and a resistor ladder DAC. We continue to be shocked at this level of sonic performance along with this feature set at this cost. Comparable products sell for $3000.00 from the competition.
The R28 features 8 fully discrete R-2R DAC modules to combine into a real balanced push/pull digital decoder as well as 4 fully discrete real balanced DSD native decoders. The DAC uses two 90/98 MHz Accusilicon 318B femto clocks to provide ultra low jitter.
The Amanero USB input supports 32bit / PCM384K PCM and up to DSD 512 asynchronous transfer. Clocking is done by a custom programmed FPGA.
The whole digital circuit is built around one custom programmed FPGA and 5 CPLD programmable chipsets to separate the different circuits for avoid any interferance in the data process in parallel mode.
The R28 headphone amp has two gain modes, 12DB in the low gain position to drive higher efficiency headphones at over 95dB sensitivity, and 22DB on high gain with the full 9.5 watts to drive any lower efficiency phones such as the HifiMan HE6 at 85dB efficiency.
The custom internal software that runs the unit is upgradable to improve sound quality in the future. All digital process mode settings are accessible by buttons on the front.
The ugraded metal remote control adds $60.00.
built like a tank
After the D/A conversion by the R2R D/A modules the analog signal is run by fully discrete matched-transistor output stages.
These high speed special ACSS output stages are zero-feedback and a current driven design as opposed to the voltage design of most other DAC's.
They are Special because almost all other designs need to convert the signal multiple times from and to current or voltage, resulting in less detail and a less defined soundstage.
The output stage in the R28 has 4 pairs of 15W transistors to offer tremendous output capability. This Diamond Differential design avoids switch distortion. It works in full Class A mode but doesn't draw large idle current. This balanced drive design lowers noise and distortion and improves the soundstage presentation and transparency. The 2022 version features 4 digital inputs and an XLR analog in.
Vacuum HE 1 XLR balanced preamplifier
The Vacuum HE1 XLR is a state of the art fully balanced remote controlled preamplifier with a built in regenerative power supply. Essentially, it makes perfect new power from the wall and then feeds the preamp. This is very similar to the PS Audio Power Plant.
The class A parallel connected power supply has very high input impedance to avoid distortion through the power supply from the newly pure regenerated power supply. It has a very low output impedance so as to be very fast and is highly linear. The preamp used a tube rectifier and no opamps inside. All caps are film caps from Solen. It is a pure vacuum tube design in the power supply and signal paths using only resistors, capacitors and vacuum tubes.
Audio-gd Vacuum HE1 XLR Tube Preamplifier Features:
- Fully balanced circuitry throughout
- Built-in regenerative power supply
- 10 tube complement
- Vacuum Tube Rectifier without silicon elements on signal and tube power circuitry
- All power capacitors sourced from Solen
- Remote control for volume and source switching
Typical preamps use a volume control run thru a potentiometer. Potentiometers are not accurate and have high levels of channel imbalance. An Alps Blue Velvet volume control is rated at +/- 2 dB which leads to poor stereo imaging due to channel imbalances. The Vacuum HE1 uses a current mode volume control. The signal only passes through a resistor and then is feed to the next stage, bypassing the volume control. The final result is less than .1dB channel balance for superb imaging.
In the Hometheater hifi review Glenn Young said:
"The Audio-gd Vacuum HE1 XLR tube preamplifier is the best sounding preamplifier that I’ve ever heard." "Considering its bargain price, I recommend it very strongly."
Read the entire review at: https://hometheaterhifi.com/reviews/amplifier/preamplifier/audio-gd-vacuum-he1-xlr-tube-preamplifier-review/
Current versions ship with a blue display but wew can special order red if that is preferrd. Allow 6-8 weeks for a special order. Remote function
17.9" w x 18.75" d x 5.2" h, with feet
Rear shot with 3 sets of balanced and 2 sets of RCA inputs/Blanced and RCA outs as well as ACSS outputs
HE-1 Regenerative power supply Real Balanced ACSS Pure Class A Solid State Preamp
The HE-1 is a fully balanced Class A preamplifierier with a built in regenerative power supply. It makes perfect new power and then supplies it to the preamp. It uses all discrete analog stages without any OP amps or coupling caps in the signal path. It has a zero feedback ACSS analog current output stage. The preamp uses three R-core transformers (In total 260W ) and more than 100,000uf audio grade NOVER capacitors are used to ensure ample and smooth power delivery. it has separate class A Power suplies for both the power regenerator and well as the fully discrete preamp that follows it. The HE-1 uses a four-channel 100 step digitally controlled relay-based volume control to yield superb channel balance. This greatly improves stereo imaging and and improves overall sound quality. It features 5 analog inputs. There are 2 RCA, 2 XLR and a single ACSS input. You even have ACSS output available to your amp as well as an ACSS, RCA or XLR inputs. The preamp can drive 3 power amps simultaneously.
Components used are all audiophile grade including DALE resistors, WIMA caps, custom order NOVER caps from England, all audiophile grade Neutrik input & output sockets and a gold plated IEC socket. In the HE-1 all parts of the four channels are perfectly match before install.
Rear shot of HE-1 preamplifier
600 watts at 2 ohms
$5,499.00 a pair
The Master 2A is a 100 watt pure Class A mono amplifier that will do 150 wats in Class A/B. It doubles into 4 and then again into 2 ohms to 600 watts. It produces 400 watts of pure Class A power at 2 ohms.
The Master 2A is a fully balanced design with both its gain stages and pre-driver stages working in class A. It is built with discrete analog stages without any OP Amps or coupling caps in the signal path.
The output transistor stages are super linear with 100W pure class A into 8 ohms moving to A/B up to 150 watts into 8 ohms.
There are 2 analog inputs: XLR and ACSS.
The amps use 80 ON Semiconductor transistors to support this huge output.
The capacitance of the whole machine is 260,000 uF, with two circle core and two R cores transformers and totally separate power supplies for the right channel and left channels.
There are a total of 4 high-quality class A parallel connection Power supplies to run the gain stages.
The amps use all audiophile grade components including DALE resistors, WIMA and custom order English NOVER power supply caps.
The amps use a Real Balanced ACSS Non Negative Feedback Power supply design with the patent pending Applied "Linear Fidelity" Technology unique to Audio-gd.
The amps weight 80 pounds each.
Signal to noise is greater than 110dB and gain is 26dB. Input sensitivity is 2.2v for full power thru the XLR inputs.
Sonics are even better when mated with an Audio-gd preamp thru their unique ACSS circuit.
They are a steal for under $5,000.00 for the pair.
Master 3A Class 50 watt Class A/ 90 watt AB power amplifier
The Master 3A is a 90 watts per channel stereo power amplifier that runs the first 50 watts in pure Class A. Both channels do 90 watts at 8 ohms, 180 watts at 4 ohms and 360 watts at 2 ohms.
The Master 3A uses a Real Balanced ACSS Non Negative Feedback design. It supports both XLR and ACSS inputs from an Audio-gd preamp. It features Applied "Linear Fidelity" Technology with a Soft Start Power Design. The amp uses 24 output transistors. The Master 3A is a fully balanced design with the the gain stages and pre-driver stages working in pure class A. The amp uses fully discretete analog stages without any opamps or coupling caps in the signal paths. There are 2 analog inputs, XLR and / ACSS.
The output stage uses a total of 24 ON Semiconductor transistors. The capacitance of the entire amp is 140,000 uF, with two circle core and two R cores transformers (Total 1600W) and totally separate power supplies for the right and left channels. There 4 groups of high-quality class A parallel connection power supplies to supply the gain stages. The amp uses all audiophile grade components, including DALE resistors, WIMA caps, custom order NOVER (UK brand) caps as well as audiophile grade input & output sockets and a gold IEC socket. The non negative feedback output drive stages uses applied "Linear Fidelity" technology that is a patent pending exclusive Audio-gd design.
Weight is 88 pounds
Size is 18.9"W x 17.3"(D) x 7.5" (H) (MM, Fully aluminium )
Master 10 remote controlled integrated amplifier
250 watts per channel / 500 watts at 4 ohms / 1000 watts @ 2 ohms
The Master 10 is a fully balanced 250 watt per channel remote controlled integrated amp. It is a monster weighing in at 75 pounds and putting out 1000 watts per channel into 2 ohms. It features 2 serts of XLR balanced and 2 sets of single ended RCA inputs along with a IEC power inlet. The Master 10 uses AGD's "Linear Fidelity" technology on the output drive stages. The output drive stages have no negative feedback but can keep the distortion low and steady with an excellent linear performance. It uses a Four channel 99 step digitally controlled relay-based volume control to avoid channel imbalance and improveed sound quality. The output stage uses 24 ON Semiconductor transistors. The amp does 250W X2 into 8 ohms, 500 watts into 4 ohms and 1000 watts at 2 ohms. Whereas most of the competiton in this price range has a signal to noise ratio in the 100-105dB range the Master 10 is 115dB. Compare this amp to the competition at $7,500.00-$10,000. We did, and were shocked.
- Fully balanced design, the gain stages and pre-driver stages working on class A built by discrete analog stages without any OP amps or coupling caps in the signal path.
- The output transistors stages work in high idle current state. The Diamond Cross output stage design avoids “switch distortion” as well as class A amps
- Non- feedback ACSS analog amps .
- The capacitance of the whole machine reaches as high as 140,000 uF, with two 750W circle core and two R cores transformers (Total 1500W) and separate power supplies for the right channel and left channels.
- A total of 4 groups of high-quality class A parallel connection PSU’s power the gain stages. To achieve a high S/N, the control circuit is powered with separate regulators.
- Four channel 99 steps digitally controlled relay-based volume control avoids channel imbalance and improves sound quality.
- Applies all audiophile grade components, including DALE resistors, WIMA caps, custom order NOVER (UK brand) caps, all audiophile grade input & output sockets and gold IEC socket.
- Inputs: 5 analog inputs: RCA x2, XLR x2, ACSS x1
NFB-1 Amp- Discontinued & No longer available