Tech Notes: USB is in our DNA

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Pez

Tech Notes: USB is in our DNA
« on: 3 May 2017, 07:29 pm »

     Tech Notes

USB is in our DNA

Over a decade of development

PART ONE

Our newest and one of our most ‘challenging’ USB products, the iGalvanic3.0 has stirred interest in the technology it possesses. The following article sheds light on how we arrived at the iGalvanic3.0. It was certainly not our first ‘USB’ rodeo.



2006. A long time ago in an audio sector far, far away…
Back in 2006 when AMR first launched the CD-77 Reference Class CD player, it was one of (if not the first) to feature a USB input. Just switch it to ‘DAC’ mode, connect a laptop and enter the world of computer audio.



At the heart of the CD-77 beats the king of the MultiBit chipsets - the Philips TDA1541A. We have stockpiled these, the most rare and sought-after of ALL DAC chipsets, and now hold several thousand pieces. We plan to hold them in reserve for something special, someday. Just like a vintage bottle of Dom Perignon, they are a great long-term investment.

Picture of some of our inventory of TDA1541As


In January 2007, at CES, the CD-77 at the heart of a Computer Audio System (CAS) was really far out back then and raised a few eyebrows as attendees didn’t think what we did was possible.

We had a laptop running Winamp feeding the CD-77 with a HTC Athena ‘e-Bible’ as remote control!


http://www.amr-audio.co.uk/html/24th_Jannuary_2007.html#q13

We were already demonstrating computer audio using a Smartphone as the remote source six months PRIOR to the launch of the iPhone!


Incidentally, this was the first time we had come across ‘IZ’.  His cover of ‘Somewhere Over the Rainbow’ was bewitching. We played the FLAC file throughout the rest of the show and everyone assumed it was a CD being spun on the CD-77!

Pez

Re: Tech Notes: USB is in our DNA
« Reply #1 on: 6 May 2017, 02:51 am »
PART TWO

2008. The PH-77 Phono Equalizer with hi-res 24/96 ADC.
At CES 2008, we showcased a prototype of the PH-77 Phono Equalizer with built-in 24/96 analogue-to-digital converter. Vinyl + Hi-Res Computer Audio Recording- heck yes!



Below is a picture of the Tower of Power – a full AMR system consisting of CD/77/PH-77/several AM-77s and/LS-77 all in bi-amp configuration. The sound had power and finesse in spades.


http://www.amr-audio.co.uk/html/26_jan2008.html

Not long after the show, during a review of the PH-77 Phono Equalizer, we were asked to investigate a ‘system hum’ in the ultra high-end system of a reviewer that may or may not have been down to the PH-77. We dashed to Heathrow and ‘hopped across the pond’ to troubleshoot the system. It was one of the first major setups where we came across a ground loop.

AMR Director – Technology, Thorsten Loesch hit a nearby Radioshack beforehand and armed with a bunch of wires and meters, we went to pour over the reviewer’s system. We stood back and, along with our USA colleague Darren Censullo, we were on tenterhooks as our Thorsten went troubleshooting the system…it was like Godzilla ripping up downtown Tokyo. We still remember it vividly today as the system totaled +$250,000. The Tara Labs interconnects were similar pricing to the PH-77! All we could imagine was a shop sign that said:


Fortunately, nothing of the sort happened and, after our Tonmeister spent an afternoon there, we managed to resolve the issues. This incident was etched in our memory banks as we came to realise how quite common place this was. This instance sowed the seeds for USB, grounding and galvanic isolation in future products.

2009/10. The 777 – Galvanic Isolation makes its first appearance.
The launch of the AMR 777 Premier Class saw the introduction of galvanic isolation after the USB to digital audio conversion stage in the CD-77.1 and CD-777.


This required designing in ground-up and dealing with jitter introduced by isolation stages.



In 2010, the AMR 77 series also saw the 77.1 revisions make their debut for the CD-77.1 with galvanic isolation and AM-77.1.

Pez

Re: Tech Notes: USB is in our DNA
« Reply #2 on: 10 May 2017, 05:20 pm »
PART THREE

2011. The DP-777 Digital Processor. Two DACs in one.
The DP-777 was the first DAC with TWO DACs to select from. With galvanic isolation, full high-resolution audio and Asynchronous USB – using the Global Master Timing clock system and Zero Jitter system for USB, S/PDIF-AES/EBU - its ability to neutralize jitter was second-to-none.

It remains a one-off DAC that could switch chipsets and is still exceptionally well regarded. Even today, some six years after its launch.



The DP-777 was our first product to feature the XMOS USB chipset. As early adopters, we worked and have continued to work closely with XMOS and have gained extensive behind-the-scenes knowledge, much beyond the datasheet. This is why we have different versions of XMOS firmware (customized in-house for our USB DACs) to perfectly suit different customer needs.

Further XMOS customization reading:
http://www.head-fi.org/t/711217/idsd-micro-black-label-tour-details-page-147-release-info-page-153/510#post_10545817

The Computer Audio Source (CAS) and Active USB cables.
To show-off the capabilities of the DP-777, and because computer audio servers were just a pipe dream back then, we developed our own Computer Audio Source using a HP Touchscreen computer. With its touchscreen navigation, stripped down hardware running an SSD and maxed out memory – was this one the first dedicated computer audiophile system?



Here is a video of the AMR Touchscreen Computer Audio Source + DP-777 on an SET with horn speaker system!


Click image for video.

When we used this device at shows and in customer homes, we quickly realised the need for a VERY long USB cable of up to 15 metres. Naturally, an active USB cable was needed to run from one side of the listening room to the DAC in the centre/front of the room.

We were quite aghast that the bog standard active USB cables comprehensively outperformed passive expensive audiophile cables. Not quite the outcome we had expected.

This made us investigate further. This was our very first experience of REclock/REgenerate/REbalance technologies.

However, the state of the computer audio industry at the time was not conducive to good sales of such a product. The active USB cable project was put on the back burner.  Little did we know how much we were going to revisit this technology in the future!

Pez

Re: Tech Notes: USB is in our DNA
« Reply #3 on: 10 May 2017, 05:27 pm »
PART FOUR

2012. The iUSB Power. A new sector is born.
With the launch of AMR’s baby-brand ‘iFi audio’ at the Rocky Mountain Audio Fest, the iUSB Power was in the first iFi wave. Audiostream was one of the first to review this new iFi product.



http://www.audiostream.com/content/i-fi

We realised back then that:

i.   Clean USB power and
ii.   Good ground isolation had a huge impact on the sound quality.

The iUSB Power was one of, if not the very first, USB audio improvement devices to offer sonic benefits to the growing market of US$1,000 USB DACs that were USB-powered (hence VERY sensitive to USB power quality). Including the iDAC, they all benefitted greatly from the iUSB Power.



One of our first reviews was organized with Stereophile.  We took the iDAC and iUSB to Art Dudley. While the visit went fine, we most fondly remember Art’s dog, Chatter (though many including us kept calling him ‘Jitter’) who was quite a hyper-active dog jumping around and about as mad as a box of frogs.



2013. The iPurifier. REBalance the USB signal.

The USB signal is balanced. Few consider it important to balance the signal that becomes unbalanced along the transmission process.

The REbalance technology was developed specifically to address this. This gave us the impetus to a new chassis around which to develop the active range in the next generation and to use different connectors for different applications.



Here is a picture of the iPurifier used in a setup by recording engineer Francesco Campbell in Italy.


https://www.facebook.com/pg/iFiAudio/photos/?tab=album&album_id=651774948191584

Pez

Re: Tech Notes: USB is in our DNA
« Reply #4 on: 25 May 2017, 03:57 am »
PART FIVE

2013. The Great USB 3.0 Crisis.
It was not all smooth sailing. In 2013 we started to receive reports that the iDSD nano was not working correctly with the latest Mac laptops. After much hair pulling, cussing and copious amounts of black coffee, working closely with XMOS, we were able to pin down the problem.




It turned out that that the latest Intel chipset's USB3.0 hardware was actually not 100% backwards compatible with the USB2.0 standard. How these chips ever passed validation and formal USB testing - well, one has to email Intel. Now in theory, Intel and Apple should have gone and fixed this mess. But they just shrugged and replied "You want us to recall millions of laptops and computers – don’t think so."

The bottom line was that there were millions of machines out there and more coming by the day, with USB systems that had USB2.0 broken on the (often only) USB3.0 ports and not only our products, but every product using XMOS Audio ended up not working. Ohhh my.

https://superuser.com/questions/482179/usb-3-0-ports-backwards-compatibility-problems-with-2-0-devices

There was a workaround in disabling the USB3.0 hardware in the BIOS for Windows and a by far more involved sequence of actions on Apple Macs. In practice, it proved difficult to convince our customers that the fault lay with Intel and that they needed to disable USB3.0 (even if they were not using any USB3.0 devices).

Thus, it was clear we had to fix the XMOS firmware, in such a way that would not only work well with the new Macs & PCs but remain fully USB standard compliant. It took many nights burning the midnight oil by both software teams (XMOS and our own) before suitable firmware updates could be made available.

If we learned anything from this episode (other than more about the inner workings of the XMOS USB Audio solution than we ever wanted to know, though it came in handy later), USB3.0 was here to stay and to ignore it would be pure folly.

We learned a great deal from this incident. The lesson was that Apple and other PC makers were moving to USB3.0. As the old adage goes, “the trend is your friend.”

To us, back then, we saw USB2.0 in the same light as the Nokia3310 (original) well, kinda old.