VELVET SOUND Sound Philosophy

Sound Philosophy
Real Live Sound

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An accurate, "reproduction of the original", is the VELVET SOUND philosophy.
AKM duplicates all sound elements contained in the, "original source".
AKM provides an active space just like a live performance.

The History of AKM's SRCs
Production Records Since 2002

Asahi Kasei Microdevices (AKM) has been brushing up the digital signal processing techniques such as digital filtering, over sampling and signal interpolation in ADC and DAC developments since 1987. In 2002, AKM developed their first 20-bit SRC product with these techniques. AKM’s SRCs, including 24-bit products released later on, have been adopted professional audio instruments that are manly used for sound source making.  
SRC products were left behind comparing with ADCs and DACs since the premium audio lineup released 32-bit product in 2010. Therefore, AKM had started developing further variation of SRC based on digital signal processing technologies that are developed with ADC and DAC, and managed to release the AK4137, a 32-bit SRC with the world class THD performance in 2015.

The History of AKM’s SRCs Production Records Since 2002

Sound Philosophy
Real Live Sound

AKM’s SRCs aim to reproduce the data as close as possible to the original analog sound by reducing noises and increasing the resolution. Therefore signal interpolation is executed on an ideal time axis without changing original recorded source.

Chang from T1 to T2 with keeping signal waveform

VELVET SOUND Architecture

Design concepts to pursue and achieve
the, "intensity", and the, "amount of information".

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the architecture of new generation audio devices.
Velvet Sound's philosophy is a combination of
measured performance and human listening tests,
because ears will always exceed any test measurement.

"Large Amount of Information and Sound Strength"
Design Concepts to Achieve

As the basic concept to represent all of the elements of sound, such as components of the fundamental wave and harmonics, sound pressure, changes in the time domain, the presence of small signal components, the difference between treble and bass of attenuation, etc., AKM has built a new VELVET SOUND architecture.

Amount of information:
Delicate Sound Reproduction thorough Noise Optimization

VELVET SOUND architecture has enabled the expression of elusive sounds by enabling a highly noise-tolerant design.  Verifying and identifying the noise mixing paths from every angle is particularly critical to reducing noise sources required for operation of digital and switching circuits.  Furthermore, not only the signal path line itself, but the internal reference signal and clock that determines the time information are separated through layout isolation to thoroughly eliminate influence by noise.  System noise beyond the audible range also reduces more than 40dB compared with the conventional products simplifying the external circuit design.

Pursuing the, "feeling of sound"
Sound beyond the audible range

Human's audible frequency range is believed from 20Hz to 20kHz, but AKM's next generation products cover up to a 200kHz signal range, enabling the expression of, "feeling sound", beyond the audible range.

VELVET SOUND Core Technology

Core Technology
Technologies representing the, “Spatially Expressing Sound”,
exceeds the numbers.

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the core technology of AKM's new generation audio devices.
This technology features “Over Sampling Digital Signal Processing Technology”
“Ideal Signal Interpolation Technology”
– Necessary for keeping the original sound colors.

Technologies representing the, “Spatially Expressing Sound”,
exceeds the numbers.

In addition to our 25 years of accumulation of experience and know-how of audio device development, an "evolved ΔΣ modulator", "evolved switched capacitor filter" and this development of new VELVET SOUND technology have achieved the "sound feeling" beyond the audible range.

Ultra-low distortion
“Over Sampling Digital Signal Processing Technology”

This is an essential technology for signal processing based on delta-sigma modulation that is AKM’s strong technology. AKM has been developing necessary technologies for over sampling digital signal processing in its development of ADC and DAC. The SRCs realize signal conversion to any rates with this over sampling technology + IRD (digital filter).


Ultra-low out-of-band noise
Ideal Signal Interpolation Technology

This technology extracts the sampling signal that corresponds to the output rate from a signal that is decompressed by over sampling digital signal processing. With the ideal signal interpolation technology, AKM’s 32-bit SRC achieves THD+N=-150dB and DR=186dB.

Ultra low out-of-band noise Ideal Signal Interpolation Technology


Key Features
Fully compatible with, "Hi-Res", sound sources
up to 768k PCM and 11.2M DSD. 

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a key feature of AKM’s next generation audio devices
which are equipped with specs and performance
for the, "Hi-Res", digital audio era.

Detailed and High Resolution Sound that Achieves
“More Original, Natural Sound”

AKM’s SRC adopts 32-bit resolution and supports digital signal conversion up to 768kHz PCM and 11.2MHz DSD format. 

Wide Range Support of PCM/DSD

The SRC realizes PCM/DSD mutual conversion and even supports DOP (DSD over PCM frame) format. It provides a suitable solution to diversifying data environments.

Controls the transient response of the signal
Sound Color Digital Filter (SCDF)

Focusing on the waveform in the time domain, the built-in 32-bit, 8x digital filter, controls the transient response of the signal. 4 types of digital filters allow music playback in a variety of sound settings by switching the filter type.

Sound Color Digital Filter

Premium Sampling Rate Converters

Product Portfolio

Product Portfolio -Premium SRCs -

* Bubble Size = "Sound Quality"

Premium SRCs

AKM released a flagship stereo SRC, the AK4137, that achieves the world highest level -150dB THD+N and168dB DR. Furthermore, the AK4136 that corresponds to wide range of use cases is line-upped. From high-end to middle range audio systems can be realized appropriately.

VELVET SOUND AKM Pursues Real Live Sound with both Roomy Sound & Sound Dynamics