Audio-GD R-27 MKII - Fully Discrete R2R All-in-One DAC/Amp

Delivery time on request.
(All devices are handmade to customer order)

The ultimate all-in-one device!

• Fully balanced, fully discrete r2r ladder DAC
• Fully balanced, fully discrete headphone/preamp -
  
  

Design overview

• Fully discrete components are used in a truly balanced power transfer design.
• 4 sets of fully discrete and independent DSD hardware decoders.
• 8 sets of fully discrete R-2R DA modules to form a symmetrical two-channel push-pull decoder.
• 2 top-of-the-line Accusilicon TCXOs with frequencies of 90 and 98 MHz ensure synchronization of the entire device and are used for playback of all data rates without PLL upscaling.
• Both the USB and HDMI inputs are equipped with isolators and a linear power supply that separately powers the USB and HDMI modules before the isolators to avoid interference from signal sources.
• USB uses a two-way transmission isolator, which not only transmits IIS signals to the FPGA processor, but also receives the synchronous clock signal sent from the FPGA processor. The USB interface itself is no longer equipped with clock generators. The synchronous clock is used to make the signal transmission more accurate and raise the sound quality to an excellent level. This significantly improves the sound quality.
• The HDMI module is now equipped with an independent isolator to improve the sound quality of the HDMI input.
• A firmware update can convert the IN2 coaxial input to an external 10MHz clock input (75 ohms).
  
• All digital mode settings can be changed live on the front panel.
  
• On the back of the device there is a port for firmware upgrade (no need to open the cover to upgrade the firmware).
  
• Unique true ACSS non-reactive headphone amplifier with four channels and non-reactive output stages consisting of 8 transistors, each rated at 15A/150W. The capacitance of the whole machine reaches up to 25,000uF. Three R-core transformers with a total power of 150W are used.
  
• Large output power 15W into 25ohm, 1300mW into 300ohm, which can easily drive most headphones.
  
• Multiple information display, support user custom display information area.
  
  

Unique jitter elimination technology

Jitter has always been considered the main reason why digital systems sound quality is inferior to high-end analog systems.
In some traditional DAC designs, the clock processing method is to follow the clock of the signal source and to restore it, and some designs also offer the possibility to reduce jitter, but with limitations when the jitter level is large.

This common solution gives good measurements in laboratory tests. In practice, however, most signal sources have large jitter values, so that the resulting sound quality is not satisfactory.

Unique, true, feedback-free ACSS beater/preamp technology

R-27 MK2 built in a true balanced design. Application of the latest ACSS design. It seems complex but in fact they are the simplest design the world has ever had, it's a lot of components to handle the power supply.The amplifier built into the R-27 MK2 has only a single "voltage gain stage" for signal processing, but operates in ACSS mode, so it is actually a current gain stage instead of a voltage gain stage, while normal OPA chips already contain two or three voltage gain stages in the simplest and shortest signal path produces the most neutral and least colored sound.

The R-27 MK2 uses a single-stage, ultra-low distortion ACSS amplifier and is soldered directly to the motherboard. The amplification stages and the diamond cross output stage operate in pure Class A operation.

ACSS is a zero-feedback technology that uses fully discrete amplifiers. Most people know that the global feedback design can perform better in test measurements, and non-feedback does not perform well in test measurements but sounds better to human ears.

There is a conflict between the classic circuits here. However, the ACSS opens up a new field, it can offer a less colored, more neutral sound with very low distortion and high linearity. So it can keep the dynamics, detail and neutral sound but not sound bright or harsh.

All signal amplification is in the form of current, which is achieved by the unique excellent open-loop multi-output mirror. The result is incomparably precise and extremely low distortion of the amplification signal. The entire signal path is balanced and all transistors operate in Class A mode.

The R-27 MK2 uses four channels with open-loop output stages consisting of 8 transistors, each rated at 15A/150W. The capacitance of the whole device reaches up to 25,000uF. It uses four R-core transformers with a total power of 150W.


Unique I/V conversion volume control technology

The volume control is also different from traditional technology. Conventional volume control technology is to implement volume control in the analog amplifier input stage through a volume potentiometer to reduce the signal.

The quality of the volume control directly affects the sound quality. With low quality volume control, details are lost, and imbalance of channels leads to distortion of the soundstage. Even the high power volume potentiometer, in the attenuation then gain the signal mode, still cause the detail to be lost and cause the S / N worst.

On the R-27 MK2 we have the I/V conversion volume control, the volume control only has a variable passive I/V conversion place at the ACSS amplifier output, where the output is the current signal, not the voltage signal. The volume control is an I/V conversion, and the volume depends on the conversion of current (I) to voltage (V). (Like R-2R D/A chips that output passive I/V conversion) It can keep the signal frequency band flat and doesn't lose details. It cannot affect the sound quality at any volume level.

The quality of the volume control is very important in the real balance gear. It must guarantee that the four channels of signal control accurately, in order to achieve the performance of the real balance gear. If the cool and hot of the balance signal can not guarantee accurate, the balance output will have large distortion, causing the sound quality and performance even much worse than a single end gear, wasting the balance gear design and cost.

In R-27 MK2 is a four-channel digital control relay-based volume control, by changing the tolerance 0.05% resistors to avoid the volume level for the channels unbalanced, achieve the best Performance and sound quality of the device

R-27 MK2 have 100 steps volume control, applied supper exponential volume characteristic, easy to match the volume with different power amplifiers and speakers. while changing the volume, the various relays break or close, it can slightly changing sound had at the output and disappear while changing the volume stop.

Specifications