Apple’s New DAC Patent Promises Flawless Sound Quality on All Apple Devices by Eliminating One Thing

A close look at the current DAC chip found in Apple's lighning cables. (From: Tinhte.vn)
A close look at the current DAC chip found in Apple’s lighning cables. (From: Tinhte.vn)

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Apple might have just solved a decades-old DAC problem with this new technology.

Apple has secured a patent for a new digital-to-analog converter (DAC) technology that could make sound much better in future devices. Using “static alternating fill order” (AFO) logic, this tech aims to eliminate the gain gradient errors causing distortions in current DAC designs.

How the New DAC Technology Works

How a DAC converts digital signals to analog signals.
How a DAC converts digital signals to analog signals.

Apple’s new idea fixes a problem that’s been in DAC designs since their inception.

Traditional DACs rely on an array of unit cells to convert digital signals to analog. But, not all cells are created equal. Their physical layout means some cells do more work than others, which adds small distortions that make the audio less pure.

Apple’s solution? A DAC with a fractal layout and a clever bit of logic they’re calling “alternating fill order” (AFO).

This system works like a careful conductor, controlling how the unit cells turn on in a well-planned way. As the signal gets stronger, the AFO logic balances out the individual quirks of each cell, resulting in a cleaner sound.

Basically, Apple’s patent focuses on improving conversion accuracy by addressing the issue of gain gradient errors in DACs.

“By filling the unit cell array from different sides, spatially and/or temporally, the gain gradient associated with the unit cells may be balanced to reduce error and increase the linearity of the DAC,” states the patent.
How unit cells turn on at two different levels using static AFO logic (From: USPTO)
How unit cells turn on at two different levels using static AFO logic (From: USPTO)

This can be implemented in two forms:

  • Static AFO: A fixed sequence that consistently activates unit cells in the same order. It uses buffers that output different portions of the digital signal among different branches.
  • Dynamic AFO: A variable sequence that changes based on programmed patterns for additional flexibility in managing signal conversion.

Benefits and Potential Applications

Our main goal in audio reproduction has always been to make it sound as close to the original recording as possible. And, this new DAC technology brings us close by minimizing errors in the conversion process.

The result could be:

  • Headphones that reveal layers previously hidden in your favorite tracks
  • Smartphones that rival dedicated audio players
  • Home theater systems that make you feel like you’re at a concert or on a movie set

It can also improve the signal-to-noise ratio (SNR) and help reduce differential nonlinearity (DNL) and integral nonlinearity (INL), which are critical factors in DAC performance.

But Apple’s ambitions don’t stop at audio.

For one, the design could also save power by turning off signals to branches that aren’t needed at a certain time.

Comparison between how loud different frequencies are for both a regular DAC and one using dynamic AFO, focused on the main working frequency of the new fractal DAC. (From: USPTO)
Comparison between how loud different frequencies are for both a regular DAC and one using dynamic AFO, focused on the main working frequency of the new fractal DAC. (From: USPTO)

This DAC is also a speed demon, potentially operating at frequencies north of 10 GHz.

That’s overkill for audio. But, it opens up a world of possibilities in wireless communication. Because of this, we could be looking at the core of future devices that push the limits of 5G and beyond.

Comparison to Existing DAC Designs

Apple’s approach is refreshingly novel when compared to conventional DAC designs in several ways.

First, the fractal layout allows for more even signal paths, which could make it work faster and sync better. Second, the AFO logic adds another level of improvement, dealing with subtle variations that other designs often overlook.

“A fractal DAC may have a static (e.g., same or similar) path length for the incoming data to each of the unit cells,” explains the patent.

This uniformity fixes a common weakness in regular designs where signal path variations can introduce their own set of problems.

Compared to traditional column and line DACs, Apple’s fractal design also makes it easier to spread out incoming data. This not only makes it work better but might also make the whole DAC smaller by reducing the need for exterior control logic.

Plus, the versatility here is impressive. Whether it’s dealing with thermometric or binary coded unit cells, or handling multiple phases for complex signal processing, this DAC architecture has it covered.

What This Could Mean for Future Apple Products

Patents don’t always translate directly into products. But, this technology could have far-reaching implications for Apple’s future lineup.

With this, users might see improved performance in next-generation AirPods or HomePods.

The iPhone, already a capable audio device, could also evolve into a pocket-sized recording studio. And, as Apple moves into new areas like augmented reality and car tech, this DAC could be key in creating truly immersive sound experiences.

But this isn’t just about better-sounding gadgets; it’s about improving the whole field of signal processing.

This DAC technology could be particularly useful for radio frequency (RF) signal generation, potentially improving performance in devices using 5G, Wi-Fi, LTE-LAA, and other wireless communication standards.

This means we might see benefits across all of Apple’s products, from Macs and iPhones to iPads and Apple Watches.

As always with patent grants, the timeline for implementing this technology remains unclear, though.

đź’¬ Conversation: 2 comments

  1. The picture at the top, “How a DAC converts digital signals to analog signals”, is blatantly wrong. Please fix it, so it doesn’t further contribute to that misunderstanding.

    Digital-to-analog converters don’t output stairstep signals — as you can see yourself by hooking up an oscilloscope. The analog-to-digital converter performs a transformation called a “fast Fourier transform” to convert the analog signal to digital. The digital-to-analog converter does an “inverse Fourier transform”. The DAC-output is band-limited: frequencies higher than half the sampling rate are lost. But other than that, the output is identical to the original analog input, with the usual caveats of noise introduced by any system. But there are absolutely no stair steps, nor anything approximating that.

    I’m a little surprised Apple got a patent for this. It’s a fairly obvious incremental improvement commonly used in other electronic circuits, I think inspired in those application from its application to software. The novelty, I guess, is that now it’s applied to audio?

  2. Existing DAC, even in Smartphones, are better than our recording equipment.

    The MIAD01 for example has 2*CS43131 with an THD+N of -115db and an SNR of 131db

    I would not be surprised, if Apples brand and patented technology would provide worse results. There must be a reason, why they are not providing any number.

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