Whats makes the AppleTV X so much better ?
Serious analog engineering
Dejittering the CPU/SSD/RAM/ETHERNET/HDMI as a whole is what makes it magical
Radically removing noise on ALL busses/inputs/outputs/HDMI completes the alchemy
New perceptual models of visual science were required
Applying the best analog engineering and test equip from a better era was critical
Noise measurements internally inside the AppleTV on the power supply rail
There is a radical reduction of noise
The AppleTV itself makes the performance possible because of its design
I cannot get this level of performance from anything else
The built-in power supply is the same as a $5 wall wart supply. It generates massive RF noise and because it is located inside the case it permeates the AppleTV board with noise. This RF noise also gets onto the HDMI causing jitter. This switching supply generates noise backwards thru the power cord and into other gear in your system as well.
This power supply is located 1/8" away from the CPU/HDMI board and induces noise into it.
Any power line noise is also brought right into the AppleTV and couples with the HDMI and AppleTV PC Board and chips
Because of size constraints the supply is also terrible at regulation, transit response, is high impedance and has high amounts of high frequency ripple noise.
All of these factors radically increase jitter and noise in all the components including the CPU/Ram/SSD/Ethernet controller/HDMI chip
The power supply had to go.
Removing the supply left a small but usable space.
A months long engineering project ensued to characterize and fully understand the current spectra, impedance, noise and regulation needs of the AppleTV. A lot of specialized vintage test equipment was used in this process because digital sampling based test equipment does not provide the best results with these types of projects and some custom made power supply testing gear was created just for this project.
Hundreds of hours of R & D later
Eventually the work resulted in using a exact diameter high purity solid silver wire of exact length with very specific parts placed along it in a transmission line arrangement. The exact position of each part and the exact placement in the case along with the distances between parts was all fine tuned for the exact impedances required to remove all the various types of noise. Different types of parts, each one picked by testing in the real circuit, were required for each spectra band. Special lengths of 2 types of wire were used from the transmission line strip filter to the AppleTV PC Board and a different exact type and length of wire was used as the pigtail coming out of the AppleTV. Cardas silver solder is used on everything.
The transmission line based strip filter is HIGHLY tuned to the exact requirements of the AppleTV. Each part is matched and tested with the assembly tuned to each AppleTV by hand. The space is actually a tuned RF cavity. The use of point to point wiring was far better then a PCB solution.
The AppleTV itself was the next target. This required hundreds of hours more work. The issue was the total lack of space. There were very obvious issues and improvements that were addressed including lowing the phase noise on clocks, cleaning up supplies to chips, a power input termination of the right impedance and overall RF noise control. I am not detailing this here as this is proprietary and magical in its results.
The other mods
I also did a range of other alchemy to the unit I do not want to cover in a public space
The linear supply
Linear power supplies for lab use use remote sensing. This extends the regulation and noise cancellation out of the linear and into the AppleTV X directly. The linear power supply uses a R-Core transformer, a dual regulation design using a TL431 regulator I custom select that has near mystical status in the audio field and a high current audio amp output transistor. The output impedance is tailiored to the AppleTV X input impedance. The regulation/noise canceling is extended into the AppleTV X via a 4 pin cable which is impedance matched so the regulation is extended right inside the AppleTV X. The linear has some special sauce I add to it. It has 1mV of pseudo random noise added. This noise dithers the PWM regulators on the Apple TV X board and provides a smoothed spectra output on the secondary side of the buck/boost regulators. The linear has short term DC accuracy of +- 0.0001vdc over 2 hours providing a calibration lab grade stability to all systems inside the AppleTV X producing a VERY stable HDMI output over time and VERY stable ethernet decoding of incoming signals.
The supply itself has VERY low noise
The result of everything combined was a VAST reduction of noise on the HDMI signal and MUCH cleaner eye patterns along with a vast reduction of jitter. However there was a much bigger effect from the mods. EVERYTHING was effected. The CPU/Ram/SSD/Ethernet chip all had vastly lowered noise and magnitudes reduction in jitter on all digital data lines. This effect was made far more complete because of the near zero length distances of the chip interconnection traces because of the appleTV being crammed into such a small space. The incredibly short distances of all internal signals meant no loss or jitter picked up internally and very low impedances between chips. Apple used good ground plane design in the main board and this isolated each side of components and the whole PCB is contained in a metal shell.
So the entire AppleTV X has VAST reductions of internal jitter and noise of all of its components - not just the HDMI.
This results in far lower error correction and concealment by the HDMI sink device ( TV ) which then provides far more of the original bits without loss. The lower impedance and lower noise floor combine for a better impedance match on the HDMI and better physical layer measurements across the board which delivers more unerrored bits to the sink ( TV )
The overall result in picture and sound is startling. The picture has more detail, better color accuracy, better motion, better gamma and the improvements are not subtle. Bit rate no longer seems important. HDR is unneeded. 4K, 2K and even SD are all great. Everything is suddenly eye candy and its very addicting. The sound becomes far more detailed, more natural, more analog. Imaging improves in vast magnitudes. Depth, placement, size, space and delineation suddenly appear like a high end DAC was rendering them. Everything has texture, dimensionality and emotion.
EVERYTHING improves. Old TV shows from the 50's, 4k feature films, even commercials can become ear/eye candy.
It is hard to believe a streaming service can be as good as what you see and hear.
Quotes from customers: "Holy shit" "Incredible" "Pantone accurate" "Breathtaking" "Emotionally involving" "addictive" "OMFG" "W T F" "Reference quality" All of them had a AppleTV before they got a AppleTV X. BluRay and file servers come in a distant second.
The improvements are very visible on any system, TV or projector
The AppleTV platform also does so many other things - music, pictures, screen sharing, cable/DirecTV, roon, playback from file servers, games, professional uses like Frame.io for cinematographer/production use and just 1000's of apps. All of these uses are brought to a new level of performance and all available from a single box.
THE R&D development evaluation systems
The evaluation and R&D of the picture and sound is done on a number of systems and with a number of beta participants. The reference system consisted of the following components reduced to the items that are reverent to the AppleTV X eval. The system is covered in this article Video walk thru 5 years ago with construction details but with older equip
Other systems and gear used for Eval consisted of Sony OLED flat panels, A 1080 HD Panasonic Plasma, Various projectors, various flat panels and a large range of audio systems from TV speaker bar to 2 channel system to full Atmos like the reference system.
Engineering done by Chris Stephens