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A Story of the EVGA Nu Audio Card engineered by Audio Note UK

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Publisher’s note: Audio Note UK has graciously provided the following article detailing the conceptualization and design of the EVGA Nu Audio Card in collaboration with EVGA.

The article is authored by Andy Grove of Audio Note UK.

(The EVGA Nu Audio Card is scheduled for launch on January 16, 2019. Price is $249. See the Audio News announcement.)

Audio Note (UK) released its first integrated amplifier, the OTO PP, in 1991 and it is a testimony both to the amplifier’s design and also to the company’s longevity that it is still possible to buy the same model today, still built completely in their factory in Sussex, England, over 25 years later. While other manufacturers come and go, as do their products, Audio Note (UK) has stood the test of time and is now Europe’s largest and most prestigious manufacturer of ultra performance valve based home audio systems. The company is one of the few to offer complete in-house designed and manufactured systems. From the tip of the cartridge on the turntable, through the cables and amplification, right through to the drive units in the loudspeakers, everything is designed and produced by Audio Note (UK) in their factories in the UK and Europe. A vast range of different options is available to suit every music lover’s requirements (there are over 150 separate and distinct products currently in the Audio Note (UK) catalogue), from cost effective solutions to full systems that truly redefine the limits of performance and ones expectations of sound quality. As the company’s motto says; ‘Music’s Finest Conductor’.

The connection between Audio Note (UK) and EVGA goes back a long way. Andrew, CEO of EVGA is a lifelong, dedicated audiophile and music lover, and when he was seeking the best system to explore his passion for the recorded arts, he of course chose Audio Note (UK). The driving forces behind the two companies have a lot in common; Andrew, Peter Qvortrup, the head of Audio Note (UK) and Andy Grove, the company’s designer in chief are all driven by the desire to make the best products possible, regardless of the development costs and challenges that may occur. Audio Note (UK) has taken this commitment to excellence to levels unseen in the audio industry for decades, not only building a vast range of ultra-performance audio products but also a wide selection of exclusive internal components, some of which can be found in the NU Audio soundcard. So it was only natural that the two companies should decide to collaborate on a ground-breaking project.

 

Power supply

The inside of a PC is not a friendly environment for audio signals, with potential interference coming from high power switching PSUs and the motherboard and GPU modulating the voltage lines, so a great deal of attention has been paid to the Nu Audio power supply design. The result:

3.3V and 12V inputs by SATA connector come direct from PSU, plus a local SMPS to convert from +12 to +/- 16.5v then to +/- 14.5V and +/- 5V.

Multi stage regulation is also used, including TI low noise ICs at +/- 14.5V and +/- 5V. We also implemented dual ground planes; one for analogue, one for digital, to reduce noise transfer.

Audio Note (UK) Standard, Nichicon solid and Panasonic FC capacitors are extensively used, together with high-performance MLCC types. All audio circuitry uses Audio Note (UK) Standard capacitors in the power rails, and the method of multiple bypass pinning is used, where many smaller capacitors are used to pin the + and – rails relative to the ground planes.

 

Digital and control

A USB based solution was chosen. USB Audio class 2.0 is a highly developed standard in HiFi and Pro Audio, therefore allowing ideal implementation of device drivers to provide superior audio quality and low latency using our ASIO drivers or WASAPI.

 

ASM1042A PCIe USB bridge

This provides a highly reliable and compatible solution for on-board PCIe-USB connectivity.

 

XMOS xCORE-200 USB solution

XMOS, a UK based semiconductor company, are widely regarded as the producers of the best USB audio solution available, which is used by high-end audio and Pro audio manufacturers around the world, in all price brackets. Low latency ASIO drivers were developed in-house at EVGA, in partnership with the German company Thesycon. Furthermore, graphic EQ DSP is carried out within the xCORE-200, minimising stolen CPU cycles.

XMOS Product Page:

https://www.xmos.com/developer/silicon/xcore200-usb

 

NDK NZ2520SD series low jitter clock oscillators

Independent oscillators are used; one for 44.1kHz sample rate multiples, one for 48kHz multiples. These provide precise, low-jitter local clocking for the ADC and DAC sections and, importantly, asynchronous/isochronous operation is supported.

It’s often stated that ‘bits are bits’. This may be true in a static reference frame but audio is a real-time, dynamic frame, therefore it’s not just the bits that are important, but also their timing. Small, fluctuating errors in timing are known as jitter and cause noise and distortion, and in ways that are not directly comparable to the analogue domain.

Local on-card clocking, using asynchronous/isochronous operation, minimises jitter.

NDK oscillator product page:

https://www.ndk.com/en/products/search/clock/1190904_1433.html

 

DAC

AKM AK4493 32 bit, 126dB DNR capable D/A converter solution. After extensive testing, evaluation and listening for over 20+ years, based primarily on sound quality, Audio Note (UK) chose to work with AKM.

All modern, high quality D/A converter ICs should have exemplary electrical performance, however all are not equal when it comes to sounding good. AKM’s proprietary technologies such as ‘Velvet Sound,’ and their use of advanced materials for the silicon, lead frame, and chip packaging, results in a superior sounding converter.

In addition, the Nu Audio card provides access to the AK4493’s selectable digital filters. This allows the user to select the filter best suited for gaming or music, and different sample rates to fine-tune the experience. For example, it is possible to optimise timing dispersion, which increases positioning accuracy and the sense of space.

All sample rates, from CD (16 bits / 44.1kHz) up to 32bits / 384kHz in PCM and DSD256, are supported natively. That means the Nu Audio card can play just about any audio or gaming format.

AKM AK4493 product page:

https://www.akm.com/akm/en/aboutus/news/20171208AK4493_001/

 

Line Out:

The AK4493 provides a fully balanced output for low noise, low distortion operation, and feeds a fully balanced, iteratively optimised, linear phase low pass filter formed by TI LME49724 fully differential amplifiers, Audio Note (UK) ¼W resistors and Wima precision capacitors. The balanced signal is fed to the line stage itself, formed from an ADI AD8056 ultra high-speed dual operational amplifier, selected for its superior sound quality. This chip is seated in an IC socket to facilitate interchangeability;a process known as “op-amp rolling”.

Again, although operational amplifiers, resistors and capacitors are not supposed to sound any different to each other, the fact of the matter is, they do. Why this is the case is complex, and poorly understood. At Audio Note (UK) we have the most sophisticated electronic test equipment at our disposal, such as Audio Precision’s APx555, and we spend a lot of time testing a host of components in our research lab.

Yet, there is one instrument we trust more than that fine piece of equipment – our own ears.

 

Extramission

It was once thought that our ability to see came from active rays which emanated from our eyes, a process known as Extramission. This theory of sight remained popular for a thousand years, and, in fact, a study has shown that many people today still believe this is so!

Of course, we now understand more about the biology and physics of vision. We know that the eye functions as a kind of camera, with a focusing lens, and we understand more about light, in both its wave and particle interpretations. All the while, however, we have been able to see. Even though a certain theory could not correctly describe the mechanics behind it, vision has been there all along, in us, and in animals.

The same is true of audio, and how we hear. Current measurement methods, although useful, are unable to satisfactorily model human aural perception, particularly of complex signals such as speech and music. Take the example of someone familiar calling out your name in a busy railway station. You turn and see your friend there because you recognise their voice and can locate it. We all know how we can recognise people by their cough, or laugh, or footsteps, or the sound of their car pulling up outside. All of this, and more, we take for granted every day, yet, the measurements used routinely in audio are hopeless at giving meaningful results in these circumstances. They are, after all, just plots of frequency, amplitude and time.

Those who dogmatically quote measurements as the final arbiter of sound quality will often hold the lack of measurable data supporting audible differences as evidence that such differences do not exist. But this ignores a fundamental point that is often misunderstood; the absence of proof is not proof of absence. Unfortunately, the fall-back position is the group-think of ‘common sense’, and let us not forget that it was that same ‘common sense’ which brought us Extramission.

 

Headphone Out

DSD is a one-bit format, and cannot be processed by standard DSP. All the better for sound quality one might think, but that does leave the problem of controlling volume. Windows volume control, as with all software digitally implemented volume controls, works by DSP. Therefore, it cannot be used on a DSD stream.

To make the headphone amplifier usable with DSD, (and of course, to overcome potential safety concerns when switching from PCM to DSD, with the resultant disabling of the existing volume control setting in Windows) we have provided a software controllable, analogue volume control for the headphone amplifier, implemented with the Maxim DS1882 IC. This chip is proven to sound good in a variety of audio equipment, and thoroughly tested in the Audio Note (UK) lab and listening room.

The integrated volume control also overcomes the issue with different headphone impedance and sensitivity, and in much finer steps. The headphone amp itself is formed from an ADI OP275 dual op-amp, chosen by extensive listening tests, and mounted in an IC socket for fine tuning, together with two TI LME49600 power buffer ICs.

Once again, Audio Note (UK) resistors and capacitors are used, including large 1000uF local capacitors to provide a reservoir of power, improving bass slam.

The 1996 IEC 61938 standard recommends headphone amplifiers have an output impedance of 120 ohms. In the real world, this is often less, but still more often than not, too much. The result is bloated one-note bass and uneven frequency response due to insufficient damping of the headphone diaphragm, and increased distortion, which manifests as a grey, sterile sound.

In the Nu Audio card, the headphone power-amp is direct coupled to the ¼ in jack, and a special circuit scheme is implemented to create high frequency stability. There is also current limiting to 250mA, which minimises the possibility of damage being caused by a momentary short-circuit during jack insertion.

The output impedance of the Nu Audio card is a small fraction of an ohm; your headphone cable will have more electrical resistance! This results in tight, defined bass and improved tone, especially when using headphones with rare-earth magnets, which have a tendency to sound tonally sterile.

 

Line In

The Nu Audio card provides a studio quality Line In interface, which is capable of recording at 384kHz, if your PC and DAW are capable of handing this data rate.

Input buffering is provided by a TI OPA1652 dual op-amp, followed by low-pass filtering. This balanced signal then drives the ADC via TI THS4551 fully differential amplifiers, using Audio Note (UK) Standard and Wima capacitors.

 

ADC

Once again, we chose to work with AKM for signal conversion. This time, the AK5572 – a 32 bit / 384kHz , 121dB capable A/D converter – was chosen, to faithfully transfer your content to the digital domain. As with the DAC, this IC is equipped with AKM’s ‘Velvet Sound’ technology and selectable high-pass and low-pass digital filters.

The Line Input is a very high quality interface, intended for use at Line level.  It can be used, for example, to record the output from a mixing desk, tape-recorder or external mic-preamp. Its specification actually exceeds that of much ‘pro’ equipment!

AK5572 product page:

https://www.akm.com/akm/en/product/datasheet1/?partno=AK5572EN

 

Mic In

The Nu Audio card sports another, fully independent input, which can be configured for both Line Level signals and Mic Level signals. It also has an inbuilt software-based level control to ensure compatibility with a wide range of sources, without the need for an external preamp.

Here we used a Cirrus Logic IC, the CS5436. This chip is 24bits / 192kHz capable, with a maximum dynamic range of 103dB.

CS5346 product page:

https://www.cirrus.com/products/cs5346/

 

Construction

Every detail of the Nu Audio card has been considered, right down to the PCB. A high quality silver and gold plated multilayer board was chosen, with isolated ground planes for analogue and digital circuitry.

Furthermore, the Nu Audio card is aesthetically appealing, with a stealth exterior and programmable RGB lighting, which can be disabled for strict audiophile performance.

Finally, it’s easy to create a kind of incoherent ‘dream-team’ of a product; there are many out there. What is important is the chemistry – or maybe alchemy – of the product, and how it performs and sounds as a whole, in a real world system.

Can it be something more than the mere sum of its parts?

Master painters are able to create their own completely individual and personal paints and colours, and at Audio Note (UK), we do something similar through our constant R&D work. We research and develop components and technologies, which then feed down into our products, and that’s where the real magic takes place, in the final work. Something transcendent is created, something which brings happiness and enjoyment to our lives.

 

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2 Responses to A Story of the EVGA Nu Audio Card engineered by Audio Note UK


  1. Handyman NYC says:

    I have been waiting for a long time for the release of this card. Can`t wait to try in business!

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