Audio-GD – R7 MK2 – Discrete Balanced R2R Ladder FPGA Accusilicon DAC – PCM / DxD / DSD

REVIEWS

R7 mk2 HIGHLIGHTS

The first R7 was launched 4 years ago and immediately received the BLUE Moon award from 6Moons! This was the first generation discrete R2R ladder DAC developed in-house by Audio-GD. Thanks to the use of the programmable chips (FPGAs), constant improvements could be made with a software update!

In addition to software improvements, the mk2 has also received a major hardware upgrade. The improvement is quite obvious compared to the previous generation.

DISCRETE 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 “ .

CLEAN POWER

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

FEATURES OF MK2

• Newly designed discrete servo stabilised power supply to power the digital circuitry, the noise level is comparable to that of a battery, but without the dry and thin noise characteristics.
• Newly developed analog vinyl configuration can be set via the menu. (New function)
• Both the USB and HDMI inputs are equipped with isolators and two sets of linear power supplies to power the USB and HDMI modules separately to avoid interference from signal sources.
• USB uses a two-way transmission isolator, which not only sends 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 adopted to make the signal transmission more accurate and upgrade the sound quality to an excellent level.
• Display sample rate of input source
• The 10MHz clock input allows the use of an external reference clock generator
• The FPGA works in parallel data processing mode.
• Listening comparisons taught us that parallel processing mode makes the sound clearer and more neutral, with better dynamics and a more analog taste.
• The clock management design of the new architecture makes the clock work more stable, bringing more transparency and more details.
• DSD uses the built-in asynchronous clock to improve the timing, which clearly improves the clarity and dynamics of reproduction.