Pro iDSD - the official thread

Folks, RMAF!

Amazing show, amazing vibe, amazing visitors, amazing hardware! And we're there!



Many of our products are to be found at our place, including the full Pro stack (Pro iESL + Pro iCAN + Pro iDSD) and a number of fabulous headphones; Focal Utopia, Final D8000 etc.



And we have something very special in there too! The latest AMR DAC. For now we'll just put these pictures here, but in upcoming weeks we'll reveal more nfo about this machine!

 
Folks, we have something short and sweet for you today. Our Thorsten talks about Pro iDSD in the context of AMR's upcoming Diablo DAC. These two machines have A LOT in common and more nfo we'll reveal shortly. In the meantime, Thorsten himself, enjoy!

 
iFi audio – The 2018 Summary
It’s been quite the year…

Dear community,

2018 is coming to an end and we’ve decided to use this occasion to share with all of you good people a word or two. Many of our product ideas were developed from what you had to say, so we’re extremely grateful for your support. You’re the fuel to our fire, thank you!

The end of the year is also a good time to summarize what we were able to achieve in the last 12 months. Without further ado, here’s what we did:

Hardware

• March – xDSD



Before this product came to be, we knew that we had to develop something very different from what we’d done before. We thought about many things – toasters with built-in speakers, a wind-up DAC for use in the dessert…only kidding! We aimed for a portable device with wireless functionality as good as a wired connection, improved volume control and a new look. Suffice to say, we strongly believe that with xDSD we were able to deliver on all counts. The toaster has had to wait!

• May - Pro iDSD



The Pro iDSD is the most ambitious and complex product of ours to date. It started many years ago as a rather simple machine, but the more time passed, the more advanced it became. After years of suffering (and here we mean both ours AND yours, just take poor Curtis as an example), the Pro iDSD eventually came into being as a state-of-the-art desktop platform loaded with so many features that it's far easier to list things it doesn't do! Not only this, but the Pro iDSD also has A LOT in common with AMR's upcoming Diablo DAC. The former is actually a scaled down version of the latter and we're exceptionally proud of how it turned out.

• June - iFi OTG Cable



We released this item due to huge demand. It's reliable, affordable, looks sleek and there's no rocket science behind it. It does the job where it should. It's useful. Hey, if we're capable of delivering headphone amps and DACs, who said that we can't make a quality OTG cable? And nope, before anyone asks, we can’t make the equivalent Apple cable – if we could, we (and the rest of the world) surely would!!! Sadly, Apple don’t share the tech that we’d need to make one work. Would you, if you were Apple?

• June - DC iPurifier2



All our iPurifiers were developed to show that even a small and affordable item can really improve sound quality if backed by solid tech. The iPurifier2 is a step up over previous versions of this product, simply because our in-house developed circuitry got better over time. Practice makes perfect!

· July - iPurifier3.0



USB sorters have always been of utmost importance to us and the iPurifier3.0 shows our attitude towards these items. This product might look nothing like our nano or micro iUSB3.0 machines, but its roots are the very same. It was designed to audibly improve the USB interface and very positive feedback from you guys out there showed us that it does just that! Thank goodness!

• October – xCAN



Yet again X marked the spot in October! We really looked forward to releasing the xCAN. On the surface, it resembles our xDSD; they have similar set of features and they look very much alike, but the differences end there. Yes, each has finely implemented Bluetooth receiver, DAC and headphone amp in one neat enclosure BUT the xCAN is a portable and fully analogue amplifier above ALL else and its D/A conversion option is a cherry on top, whereas the xDSD - a DAC in the first place - is the exact opposite. Plus these two can work as a team and we have photographic evidence from you guys to prove it!

• November - Ear Plugs



This one you didn't expect, huh? Us neither. But then again, we like silence and it’s yet another way to give you guys a low noise floor! (Plus they can protect your ears from the squeaks of protest when your loved one finds out you’ve bought yet another piece of audio equipment!) We try to think of everything…

Software

• March - MQA firmware for all nano and micro products

This firmware was one of the most important things for us in 2018. We didn't want to include MQA functionality in just one or two products, we wanted to roll things out across all suitable iFi goods, even some discontinued models. Even though the 5.30 'Cookies & Cream' firmware has some limitations, this is the one to go after if you'd like to listen to MQA regardless of the iFi audio DAC you use.

• October - GTO filter firmware for all nano and micro products

The GTO filter was a tricky thing to develop, but in the end, it surely was worth the effort. To our ears it sounds amazing enough to surpass every other filter out there and we encourage everyone to give this one a try. Hey, it comes at nil cost, improves sound and if you don't like it, you can always use our previously released firmware. That's a win-win right there.

• November - Beta MQA firmware for the Pro iDSD

Fully operational MQA on our Pro iDSD took us a fair bit longer than expected for a reason. (Poor Curtis was turning in his grave!). The amount of work needed in order to have this signal fully decoded was nothing short of staggering. Everything had to be coded from scratch. Both our team and MQA's engineers were involved in this project and we're ecstatic that we were
able to finally have this functionality ready. Enjoy!



Additionally, one thing we’re very proud of is that we were able to push our head of sales out of the UK office for well-deserved holiday. Blindfolded, the man was in shock and had no idea where he was transported. Since no laptops or comms with his team were allowed, after the adventure he told us that withdrawal shivers kicked in hard. But once he got off the plane and acknowledged he was in Iceland… Long story’s short, after this trip he returned as a new man. Even though he’s a good lad, we didn’t miss him at all but shhh…
 
How the Pro iDSD actually works...
The XMOS Processor

The XMOS processor primarily handles the interfaces, including USB connections, SPDIF/AES-EBU connections and I2S input from the WiFi/Network audio module. All inputs are decoded, passed through a memory buffer, then DSD/DOP decoding is applied and then MQA decoding. Also, the entire user interface, display control etc. are handled by the XMOS processor – the 16-Core / 2,000 MIPS.
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From the XMOS the I2S PCM signal or DSD signal is passed to the FPGA for any filtering/conversion etc. and from there through a galvanic isolation barrier to the final re-clocking and DACs. This makes sure that all the noisy ‘digital’ processing and its noise is contained on the digital module and cannot affect the DACs and analogue side.
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The audio clock is placed next to the re-clocker and DACs and on the ‘Audio’ side of the isolation barrier. This clock is programmed extremely precisely with a < 0.04ppm precision (hence, beyond the ‘femto clock’ level) and is either fixed (USB input) or is adjusted to the long-term average of the incoming data (SPDIF/AES-EBU/I2S from Wifi) which together with the memory buffer makes sure any source jitter is ‘locked out’ completely. This system is the same as found originally in the AMR DP-777 where it was implemented in an FPGA. For the Pro iDSD we have ported it to the XMOS, which is more suited to this kind of task.
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After all that digital complexity (which is there for very good reason), the rest of the Pro iDSD is delightfully simple.
The DACs are used in voltage output mode. The signal from the DACs is direct-coupled to a RCLC passive low-pass filter at around 80kHz and from there either to the volume control and the input of line drive circuit or directly to the input of the line drive circuit.
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The line drive circuit is in essence a modern take on classic 1950's tube studio circuitry. It is conceptually based on late generation TAB/Mahaik Studio Console line-driver modules, which had two low-gain triode stages and a choke-loaded cathode follower driving an output transformer with a modest amount of looped feedback to lower distortion to what was considered ‘adequate’ by the stringent requirements of the German Public Radio/TV system.
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Our circuit is not capacitor / transformer coupled but instead Direct- Coupled and able to drive 200 Ohm (or lower) loads without the need for an output transformer. It is fully discrete and a single ‘non-op-amp’ structure modelled on the way tube circuity works, eliminating for example distortion between stages caused by the non-linear input impedance of solid-state devices compared to tubes.
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We use either triode (NOS GE 5670) or J-Fet input, with a special second stage in solid-state that offers extremely high input impedance and high linearity, similar to a triode circuit. The current drive comes not from a cathode follower, instead we use a Mosfet Follower loaded by a CCS with a ‘current booster’ using bipolar transistors as output buffer. Again, a modest amount of loop feedback is used to achieve ‘studio standard’ measured performance.

This looped feedback can be lowered to almost zero in the Tube+ setting, meaning the input tube operates without feedback and the solid-state second stage and output are enclosed in a shorter local feedback loop. This causes much higher measured distortion, subjective sound as always is a different story.
 
Pro iDSD & MQA
Some of the best things in life are worth waiting for...

The Pro iDSD firmware version 2.01 ‘Chilli con Carne’ is a ground-up complete re-write which totally replaced large chunks of XMOS code with all-new in-house developed new one, to reduce resource usage without losing functionality.

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We wanted the best features for the Pro iDSD, including the full MQA decoder.

To make room for the full MQA decoder, the entire audio subsystem was streamlined, optimised and pared down in resource use WITHOUT affecting functionality. The MQA team also worked to maximise the efficiency of their code with hand-written assembler optimisations.

That also meant redoing USB Audio, S/PDIF Audio and I2S Audio (for Wifi Module).
The full source code package for the iDSD Pro is around 75 million characters. The Encyclopedia Britannica is ‘only’ 43million so just over half as ‘thin.’

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In addition to the code re-work realized from earlier releases, there was also room for improved usability (hey, Pro iDSD is a very complex product after all), so we stepped up the testing which led to increased time between iterations. As you modify the firmware > you debug > you do limited testing (usually a few rounds in the loop) > you go to formal testing > you list the bugs and go back to the beginning. You get the gist.

It took us as long as it took because we want the product to be the best it can be. Nonetheless, we appreciate everyone’s patience!

The result? Version 2.01 (to our ears) sounds amazing.

Here's the link to the 2.01 FW for our Pro iDSD, enjoy!
(scroll down the page, files are just under the 'STEP 3:')

https://ifi-audio.com/products/pro-idsd/
 
Self-taught acoustic guitar singer-songwriter David Elias lives in Hawaii. He has played music all his life. He has written songs since earliest teen years.

He became an adventurous musician online in the earliest Internet days and began self-producing a seemingly endless menu of music and styles, settings, backing bands and artists on his own label Sketti Sandwich Productions.

In the early 2000's he helped pioneer some of the first hi-res technologies (DSD) to create the most realistic listening reproductions for listeners in both stereo and surround sound as if you are in the studio with the artists performing.

Read what David has to say about iFi's Pro iDSD: https://art-of-listening.com/…/the-ultimate-media-refactor…/
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