SU-R1000 Development Approaches
Most high-end audio amplifiers are analogue. Analogue amps boast a long history, and their sound quality improvement technologies, such as circuit systems and parts development, are regarded as having been fully established. Digital amps, on the other hand, still have great potential for further development since rapid technical advancements in recent years have enabled high-accuracy signal processing not possible with analogue systems. Given that today’s mainstream music sources are digital, such as CD and streaming platforms, digital signals should ideally be processed in the original digital format. Furthermore, devices such as AD converters are also advancing, allowing high-precision digital signal processing of analogue music sources.
Under such circumstances, Technics has been devoted to the development of digital amp technology since 2014. In creating the SU-R1000 Reference Class product, Technics took the following technical approaches.
Advancement of Digital Amp Technology
Technics has newly developed ADCT (Active Distortion Cancelling Technology), in addition to the proprietary technologies that maximise digital amps’ advantages, such as LAPC and JENO. The ADCT realises further enrichment of sound quality by eliminating distortion generated in the power stage by speaker’s counter electromotive force and power supply voltage drop.
Advancement of Power Supply
The new switching power supply system, Advanced Speed Silent Power Supply, has successfully improved the S/N ratio. Furthermore, four independent power supply units provided for different circuit blocks realise superb separation and dynamic sound reproduction. What’s more, the power devices incorporate low-resistance GaN (gallium nitride).
Technics’ New Proposal: Phono Input
There are still many analogue record enthusiasts, and they form an important market segment for Technics. The SU-R1000 is equipped with an Intelligent Phono EQ, which utilises digital technology to achieve accurate equaliser curve and delivers high sound quality by improving the crosstalk of the cartridge and enhancing the frequency characteristic determined by the matching of the cartridge and phono equaliser.
High Sound Quality Technologies Incorporated in SU-R1000
JENO (Jitter Elimination and Noise-Shaping Optimisation)
Jitter is a major cause of distortion in digital systems, and is caused by mis-timing in the master clocks used in digital-to-analogue conversion. To eliminate the degradation of sound caused by jitter, Technics has developed an original jitter reduction circuit, comprising a clock generator in the noise-shaping system to reduce jitter in the low-frequency range and a high-precision sample rate converter for suppressing jitter in the high-frequency range. Thus it reduces jitter in an ideal way over the entire frequency range. This works with original high-precision PWM (Pulse Width Modulation) conversion circuit, optimising the noise-shaping speed, the degree and re-quantisation number, and the PWM gradation, in order to convert high-resolution signals to PWM without causing any damage to the dynamic range. These technologies enable Technics digital amplifier designs to reproduce the natural and delicate nuances of music.
LAPC (Load Adaptive Phase Calibration)
Speaker impedance changes with each frequency and a power amplifier is required to drive speakers without being affected by the speaker’s characteristics. However, conventional digital amplifiers are connected to speakers through a low-pass filter at the output stage, so they are even more strongly affected by the speaker impedance characteristics. Also, although the amplitude characteristics of conventional amplifiers due to negative feedback were improved, the phase characteristics could not be enhanced. We thus developed a speaker impedance adaptive optimisation algorithm that performs correction to the ideal impulse response through digital signal processing by measuring the frequency amplitude-phase characteristics of the amplifier with the speakers connected. This new technique enables flattening the frequency characteristics of amplitude and phase, which had previously not been achieved by amplifiers, as well as delivering a sound with rich spatial expression.
ADCT (Active Distortion Cancelling Technology)
The Active Distortion Cancelling Technology newly developed by Technics accurately extracts and removes distortion in the power output stage which is generated by the speaker’s counter electromotive force and voltage drops. In the Hi-Fi audio market where an unlimited number of audio systems can be configured by combining various products, high-end audio amplifiers need to drive a diversity of speakers to the fullest. The Active Distortion Cancelling Technology accurately extracts distortion by determining the difference between the speaker terminal output and JENO output and then applies correction to the output digital signal, thus correcting the conventional digital amp system. This provides powerful speaker driving force and acoustic energy while offering the superior features of the digital amp, such as low noise, sharp sound image and expansive sound ambience, regardless of the types of connected speakers.
Advanced Speed Silent Power Supply
The SU-R1000 uses a switching power supply system to ensure stable supply of voltage and current required by the digital amp. In a conventional switching power supply system, the ON time of the switching operation was controlled in order to stabilise the voltage, and this caused the switching frequency to fluctuate according to the load, resulting in a modulation noise to affect the sound quality. The Advanced Speed Silent Power Supply has eliminated this noise by fixing the switching frequency in the 400-kHz band. Furthermore, a Super Low Noise Regulator is provided in the later stage. This prevents the decrease of regulation resulting from the fixed switching frequency and impedes the mixing of noise component into high frequencies. The result is high-response power supply that brings out the best performance from the digital amplifier.
Four Independent Power Supply Units
In the SU-R1000, every element comprising the power supply has been revamped for higher sound quality. What’s more, four independent power supply units are provided for different circuit blocks for further enhancement of sound quality. Since the SU-R1000 is an integrated amplifier, the internal circuits consist of a pre-amp stage and power amp stage in a mix of analogue and digital circuits. The Phono-EQ section which processes minute analogue signals is particularly susceptible to the effect of noise transmitted through the power supply line. The SU-R1000 uses separate power supply units for the analogue circuits and digital circuits in the pre-amp stage. It also uses separate power supply units for the right and left channels in the power amp stage that requires large electrical power. With the four independent power supply units, the SU-R1000 prevents power-line-induced interference among the circuit blocks and realises a high S/N ratio and superb separation.
Battery Driven Clock Generator
For a digital amplifier, improving the precision of the clock, which provides the important operation timing information, is the key to high sound quality. However, power supply noise from the clock circuit is a major impeding factor. The SU-R1000 is equipped with a Battery Driven Clock Generator. The use of a battery as a power supply for the clock circuit eliminates the adverse effect of power supply noise on the clock signal, thus enabling superb sound image localisation and clear sound space expression.
GaN-FET Driver (High Speed and Low Impedance Power devices)
In the power output section of the amplifier, Technics has employed a high-speed GaN (gallium nitride) FET driver device with super-low resistance. This enables the construction of a high-power amp using a single push-pull configuration, allowing the length of the large current carrying signal path to be shortened, and resulting in outstanding linearity regardless of the sound level.
Intelligent Phono EQ
The Intelligent Phono EQ mounted in the SU-R1000 utilises the sound quality improvement technology for DSP, which Technics has accumulated through the development of LAPC, in order to realise high sound quality not possible with analogue Phono-EQ. This technology consists of three parts: 1. Accurate EQ Curve, 2. Crosstalk Canceller and 3. Response Optimiser. These functions can be turned ON/OFF to suit the user’s preference.
- Accurate EQ Curve
Accurate EQ curve is achieved by a hybrid analogue-digital system. The high-gain low-pass filter (LPF) performs analogue processing, and high frequencies are raised after the A/D conversion. The use of the 40-dB LPF in the analogue region suppresses the bit loss during digital filter processing, and high frequencies are raised with high accuracy in the digital region to achieve a high S/N ratio.
- Crosstalk Canceller
This function measures the crosstalk characteristic of the installed cartridge by using the crosstalk measuring signal recorded on the Calibration Record bundled with the SU-R1000 and then performs reverse-correction using the built-in DSP to achieve significant improvement of the crosstalk characteristic. This results in sharper sound image and more expansive sound ambience.
- Response Optimiser
This function measures the frequency characteristic of the installed cartridge by using a TSP (Time Stretched Pulse) signal recorded on the bundled Calibration Record, and corrects characteristic disturbance. It corrects the effect of impedance matching. between the cartridge and phono equaliser to bring out the true sound quality of the cartridge. This technology aims to improve sound quality by providing a selector such as a switch in the high-sensitivity phono input line for the removal of the possibility of noise mixing.