R-27 (Version 2021)

DAC+earphone+preamp all-in-one, can be used separately as DAC or pure earphone/preamp

Pure Class A power up to 9000mW @ 40 ohms,

Dual gain design sufficient to drive a wide range of high and low sensitivity headphones

Fully discrete and truly balanced current transfer design.

4 fully discrete individual DSD hardware decoders.

8 fully discrete R-2R DA modules to form a two-channel balanced push-pull decoder.

Two Accusilicon clocks up to 90 / 98MHz provide synchronous clocking of the whole unit without PLL upscaling.

32bit / 384K asynchronous transmission Amanero USB interface with FPGA synchronous clocking applied.

USB / HDMI with independent isolator and isolated power supply, DXD and DSD support.

The entire digital circuitry is composed of one FPGA and five CPLD programmable devices to isolate the different functional circuits from interference.

The fastest parallel data processing mode is used, and firmware upgrades are supported to enhance the sound quality.

All digital mode settings can be done on the panel (without opening the machine).

A firmware upgrade port is installed on the rear panel of the machine (no need to open the machine to upgrade the firmware).

The full upgrade version already includes the following upgrade options.

1, two clocks for Accusilicon femtosecond clocks.

2, USB isolator and separate power supply.

3, Metal remote control.

Accusilicon clocks:

Features of the R-27 (Model 2021)：

1, Both USB and HDMI inputs are equipped with separate isolators to eliminate interference from signal sources, and an isolated Class A regulated power supply is used in front of the isolator to supply power. (New upgrade)

2.The USB interface itself is no longer equipped with a data clock. The use of a synchronous clock makes the signal transmission more accurate and allows the sound quality to be significantly improved to that of the previous generation R-27 plus DI-20 (but not DI-20HE). (New upgrade)

3. HDMI is equipped with a separate isolator to improve the sound quality of the HDMI input. (New)

4, FPGA data processing mode is parallel processing mode.

The IIS signal is serial data mode, each data requires one clock cycle, one frame of left and right channel data requires 64 clock cycles, affected by the stability of 64 clock cycles.

The parallel mode requires only one clock to transmit and process the 32-bit data of the left and right channels, which greatly increases the operating speed and is less affected by the stability of the clock.

The IIS input data (USB and HDMI-IIS) is immediately reassembled into two sets of 32-bit parallel data as soon as it is input, and the SPDIF signal is demodulated and sent to the next level of processing in two sets of 24-bit parallel data, while the DSD data is also reassembled into two sets of 64-bit parallel data as soon as it is input.

The parallel processing mode results in a clearer and more neutral sound with better dynamics and a more analogue flavour when compared to listening.

5. The new architecture of the clock management design allows for more stable clock operation and greater transparency and detail.

6. The DSD is re-calibrated using the built-in asynchronous clock, which significantly improves the clarity and dynamics of the playback.

7. SPDIF supports DOP playback.

Advantages and disadvantages of the R-2R DAC:

Advantages:

1, The R-2R does not convert the clock signal to the output signal.

2, R-2R is not sensitive to jitter but Delta-Sigma is quite sensitive.

3, The R-2R output signal level is more accurate than Delta-Sigma.

Disadvantages :

1, The harmonic distortion of the R-2R can be quite low but not as low as the ES9038 PRO (Delta-Sigma).

2, The accuracy of the glitch and step resistor is not easy to solve.

The R-2R design is popular in the market:

The R-2R has become popular in both DIY kits and factory products.

In the low cost DIY kit market, it is common to see designs that take on the old MSB technology, but only retain the signal conversion part and leave out the subtlety of the factory design. This design is a serial data input to a shift register IC to convert data to analogue signals, and is simply not the answer to the technical challenges of the R-2R, the performance of which is entirely dependent on the accuracy of the step resistor.

Manufacturers in the Hi-End market use quite sophisticated techniques to solve the problems of the R-2R in order to achieve high performance and sound quality.

Some manufacturers use the serial control mode of the shift register IC. The design shown below uses an FPGA to control the ladder resistor switch in parallel. The parallel control mode, where each bit of the ladder resistor switch is controlled individually, provides a very high speed (parallel mode requires only 1 clock cycle to output all the data, while serial mode requires at least 8 to 24 clock cycles) to send or update the data, and can correct the data on-the-fly at any time, resulting in a low distortion output signal and solving problems caused by resistor tolerances and Glitch, etc.

The serial mode requires at least 8 to 24 clock cycles to send or update the data and allows the data to be corrected on-the-fly at any time so that the output signal has a low distortion characteristic, solving problems caused by resistance tolerances, Glitch etc.

Considerable importance of FPGAs/CPLDs:

FPGAs/CPLDs are programmable logic array devices.

Today, FPGAs are used in a number of Hi-End level DACs, such as the popular ROCKNA WAVEDREAM DAC.

We have been using FPGA designs in DAC products since 2008.

The machine consists of one FPGA and five CPLD chips to form the entire digital circuit.

The hardware layout inside the FPGA can be designed and arranged by software, and the hardware can be upgraded by software updates.

When the firmware is upgraded, the hardware is upgraded at the same time. This provides a high degree of flexibility, allowing software upgrades to improve sound quality, add newer features, and keep the product always up to date.

The FPGA/CPLD with great responsibility:

1. High performance SPDIF demodulator built into the FPGA instead of the low performance SPDIF demodulator chips such as DIR9001, WM8805 and AK411X which are cured in the market.

2, Restructured clock and FIFO technology, output data can be accurately synchronized to the clock, rejecting jitter.

3, Built-in 2X, 4X and 8X digital filters and different algorithmic NOS modes for users to choose the most suitable tone for their personal taste.

4. Unique design to emulate the sound of the TDA1541+SAA7220.

Responsible FPGA:

1, Built-in high performance SPDIF demodulator instead of using the market cured low performance SPDIF demodulator chips such as DIR9001, WM8805 and AK411X.

2, Reassembled clock and FIFO technology, output data can be accurately synchronized to the clock, no jitter.

3, Built-in 2X, 4X and 8X digital filters and 4 different algorithmic NOS modes for the user to choose the tone that best suits his or her taste.

The fully discrete, pure Class A, truly balanced headphone/preamp is the same design as the Master 9:

The built-in headphone/preamp has a decisive impact on the sound quality of the DAC. The best digital circuit design, without a great analogue output stage design, the sound quality becomes extremely ordinary.

This unit is amplified and processed by a high-speed CAST amplifier. The CAST amplifier is designed without negative feedback and works in current signal mode, without having to change the signal repeatedly between current and voltage as other designs do.

The unique design advantage of the CAST is that the DA output signal requires only one stage of gain amplification to be output to the headphone or preamp output, resulting in the lowest sound coloration and the most realistic and natural sound quality.

The output buffer stage is a diamond-shaped output circuit using eight output tubes of up to 150W each, and is set to a pure Class A state, eliminating switching distortion and enriching even harmonics for a more realistic sound.

The entire analogue circuitry operates with no local or loop feedback at all.

Powerful power supply design:

The DAC is equipped with 14 ultra-high speed, ultra-low noise power supplies, which are double regulated to eliminate power supply noise and to supply the various digital sections.

Four pure Class A parallel regulated power supplies are built in to supply the analogue amplifier circuits.

Three R-type transformers with a total of 135W are used to separately power the digital circuits and the left and right channel analogue circuits.

Please note:

The R-2R requires more time for ageing due to its fully discrete design.

Aging requires that the music is played with a signal source connected. Even if the unit has been aged for 100 hours before delivery, we recommend that it is aged for an additional 500 hours to achieve optimum sound quality and performance.

Even if the customer is not listening at home, the machine can be switched on to speed up the ageing process.

Input mode:

Press the "Input" button to select the input signal source.

Input 1: RCA - coaxial input.

Input 2: Optical input.

Input 3: HDMI-IIS input.

Input 4: USB input.

Input 5: XLR analogue input.

Input 6: RCA analogue input.

Gain mode:

This unit uses a wide range of volume controls and new gain control technology. There are no in-line switches, relays or amplifier parameters to change when switching between gains, so the sound quality is identical at different gains.

H is for high gain and L is for low gain.

Low gain is 12DB and is suitable for headphones with a sensitivity of 95DB or more.

High gain is 22DB, suitable for headphones with a sensitivity of 95DB or less, even low sensitivity headphones like the HE6 can be fully driven.

The graph below shows the gain vs volume control curve.

Output mode:

Press the "OUT" button and the display will show "P , H" in turn.

"XLR and RCA can be connected to two amplifiers at the same time. When the unit is set to DAC output, the display will change to "d" instead of "P" .

"H" means that the signal is output from the headphones on the front of the machine.

Introduction to setup functions :

The DAC can be set up from the panel with internal processing functions to change different tones, or to change different controls without opening the case.

How to enter setup mode:

When you are ready to update the function settings, we recommend turning the volume down and stopping the music from the source.

Function of the "SETTING" button.

By pressing the "SETTING" button, the first bit of the display will flash, indicating that the function can be changed.

When the "SETTING" button is pressed again while the display is flashing, the first bit of the display stops flashing and the right bit of the display flashes, which means that the setting can be changed. Pressing the "SETTING" button again when the rightmost bit of the display is flashing takes the display to the leftmost bit of the settings menu on the second page.

Function of the left "INPUT" button.

When the left "INPUT" button is pressed while the display is flashing, the display will stop flashing at the original flashing position and the left display will flash, which means that the function can be changed. Pressing the left "INPUT" button again when the leftmost bit of the display is flashing takes the display to the rightmost bit of the settings menu on the second page.

Function of the right "INPUT" button.

When the right "INPUT" button is pressed while the display is flashing, the character displayed in the flashing display will change, indicating that the function setting has been changed.

When no more buttons are pressed for approximately 5 seconds, the display stops flashing and the user can restart the source music and turn the volume back up to normal listening level.

The following is a chart showing the function settings for the two page display menu.

First page menu.

Display 1 : OS/NOS (OS oversampling technology and NOS no oversampling technology)

"O" selects Oversampling technology (OS), "N" selects No Oversampling technology (NOS).

Display 2: Mode (operating mode of OS and NOS)

When OS/NOS is set to "O" the DAC is operating in Oversampling mode, the lower number OS Mode makes the sound thicker and softer. Depending on your sound preference.

Mode "0" : NOS mode for conventional technology.

Mode "2" : 2X oversampling technology.

Mode "4" : 4X oversampling technology.

Mode "8" : 8X oversampling technology.

When OS/NOS is set to "N" the DAC is operating in NOS mode, the NOS mode is upgraded to the new architecture configuration, so the display shows 1-3 and the result is only one NOS mode.

Display 3: TDA (emulation SAA7220+TDA1541A) :

Activate (1) DAC to run the emulated TDA1541A function. When the OS is set to OS0 or OS2 or OS4, the emulation of the SAA7220+TDA1541A will run. This function can have an effect on the tone in any mode.

Display 4 : Gain (Gain Select) :

H is for high gain and L is for low gain.

Low gain is 12DB and is suitable for headphones with a sensitivity of 95DB or more.

High gain is 22DB, suitable for headphones with a sensitivity of 95DB or less, and can be fully driven even by headphones with a low sensitivity such as the HE6.

Second menu page.

Display 1 : DAC/PRE (DAC/Pre Output Selection) :

"D" means that the XLR/RCA/CAST output is set to DAC and the volume control does not work in this state (the headphone output also has volume control regardless of the setting). "P" means that the XLR/RCA/CAST outputs are set to Preamp and all outputs are controlled by volume.

Display 2 : Dark (display function):

Activates (1) the automatic display switch-off function. The display will automatically switch off approximately 10 seconds after stopping any key operation, leaving only a single LED to indicate that the machine is switched on.

Deactivate (0) the automatic display switch-off function, the display will remain lit.

Display 3: Standby function:

Display 4: Remote (remote control function)

The remote control function is set, mainly for the remote volume function.

When set to 0, the volume only changes by one stop when the remote volume is pressed once or long.

When set to 1, the volume will increase or decrease continuously when the remote control button is pressed continuously.

If the machine is susceptible to interference from other devices, please set this function to 0.

Setting demonstration.

1, set to the most neutral sounding mode (8x oversampling, not emulating the TDA1541)

Press the "SETTING" button, the first display bit on the first menu page flashes, set to "0" with the "RIGHT INPUT" button and press the "SETTING" button again. "The second display bit of the first menu page flashes and is set to "8" via the "RIGHT INPUT" button, then press the "SETTING" button again. SETTING" button, the third display bit of the first menu page flashes and is set to "0" via the "RIGHT INPUT" button.

2, set to emulation TDA1541 mode

Press the "SETTING" button, the first display bit of the first menu page flashes, set it to "0" by using the "RIGHT INPUT" button, then press the Press the "SETTING" button, the second display bit of the first menu page flashes and is set to "0" or "2" via the "RIGHT INPUT" button. " or "4" (the lower the number the thicker and softer the sound), press the "SETTING" button again, the third display of the first menu page flashes and is set to "1" by means of the "RIGHT INPUT" button. "button to "1".

3, set to NOS mode (new architecture NOS, emulation of TDA1541, one of the soft and warm sound modes)

Press the "SETTING" button, the first bit of the first menu page will flash, set to "N" with the "RIGHT INPUT" button, then press it twice. Press the "SETTING" button twice, the third display bit of the first menu page flashes and is set to "1" via the "RIGHT INPUT" button.

4, Setting to high gain mode

Press the "SETTING" button four times, the fourth display position on the first menu page flashes and can be set to "H" via the "RIGHT INPUT" button.

5, Set the output to DAC mode at the back of the machine

Press the "SETTING" button four times, the fourth display bit of the first menu page flashes, press the "SETTING" button again and go to the first display bit of the second menu page flashes, set to "H" via the "RIGHT INPUT" button. INPUT" button to set to "d".

6, set to remote control volume continuous control mode

Press the "SETTING" button, the first display of the first page of the menu flashes, then press the "LEFT INPUT" button, the display goes to the fourth position of the second page of the menu, set to "1" via the "RIGHT INPUT" button. "button to set to "1".

HDMI definition : (PS audio format compatible)

The MLCK signal is not required for the unit, but will not be affected even if the source has an MLCK output

UPDATE PORT 10-pin socket.

Connect the Altera Blaster downloader to upgrade the internal FPGA firmware via PC to upgrade functionality or performance