One way in which technology appears to be moving forward.

One of the facts which I only posted about a few years ago, was the existence of external sound devices, which effectively acted as an external, USB-connected sound card, and, whether they could be made to work with certain Android software. That particular sound device had as main feature, studio-quality sound (96kHz, 24-bit).

Well, there is a more recent way to accomplish approximately the same thing:

20200627_203457_c

I should mention in what context this later technology presents itself to the users of mobile devices:

Much as Apple rolled out smart-phones with no traditional, 3.5mm stereo headphone jacks, Samsung has rolled out similar tablets, where the universal connector-type of the latter, is a USB-C port. The ‘Tab S6′ is an example of that. Thus, because some users do want to connect ‘wired’ headphones to this tablet, it’s suggested that users buy a so-called “dongle”, that adapts the USB-C port on the tablet, to a female, 3.5mm stereo phone jack, even the microphone feature of which seems to work. This one cost me CAD 22, including 1-day delivery.

A simple question which some people might have, especially if they are deeply mired in the analog days, and in the technology which existed in the 1970s and 1980s, could be: ‘Does such a dongle just connect the analog pins of the headphone socket, directly to the pins of the USB socket? If not, what exactly does it do?’

The correct answer to that sort of question would be the fact that, as small as that end of the dongle is, on the USB-C side, there is a tiny chip. With that tiny chip, the manufacturers have added a completely unpredictable amount of complexity, to how the dongle might work. Chips exist that have 100,000 transistors. And chips also exist that have 1,000,000 transistors, although that last type of chip is less common, and exists in spectacular cases, such as CPUs, GPUs, etc..

What this means is that, in theory, the chip in this adapter could do everything that the ‘Focusrite 2i2′ external sound card was able to do. But, that’s in theory. There are two important ways, in which it will fail to do so, at least at the time I’m writing this:

  1. The accuracy of that chip is in doubt, And
  2. The protocol with which the adapter communicates with the USB-C port of the mobile device, which is actually referred to as its USB Profile, has not been made backwards-compatible with the older generation of external sound cards…

 

(Updated 6/28/2020, 12h45… )

(As of 6/27/2020, 21h20: )

This particular device has been advertised to offer sampling rates of up to 384kHz, and a sample-depth of up to 32 bits. But in reality, there is no way it could accomplish both, purely from the hardware perspective.

It just might be able to achieve 24-bit accuracy, at one of the slower sample rates. But at the highest sample rate, its samples cannot be so accurate. And this is, in spite of inherent monolithic – i.e., same-chip – matching of transistors. What will happen if 32-bit depth is chosen at high sample-rates, is, that 32 bits will be sent to the tablet, but that (n) least-significant bits out of those 32 will actually be inaccurate.

Problem (2) above is actually the bigger problem…

The way in which I would have connected the Focusrite would have been, through an OTG adapter. But, by its nature, this adapter is meant to be connected without an OTG adapter. Therefore it also follows, that the way in which it encodes the data it sends to and receives from the tablet, cannot be the same, as that of the older devices was.

I have just given this idea a test-ride, with 3 Google Play apps, that were all programmed by the company called “eXtream”:

  • “Evolution Audio Mobile Studio”,
  • “USB Audio Recorder PRO”,
  • “USB Audio Player PRO”.

Normally, all 3 Android apps would recognize generic, external USB sound devices. In this case, every time the adapter is to be used with the app, this recognition fails. Instead, with “Evolution Audio Mobile Studio”, when the user is prompted by the app, whether to use its eXtream drivers, or to connect to the device as an Android sound device, the user is required to choose the less-powerful option.

As a result, with this adapter, the user can choose a higher sample-rate, such as 96kHz, but can only choose 16-bit sample-depth. This kind of makes the exercise pointless, as studio-quality recording requires 24-bit depth, to go with the higher sample-rates.

‘USB Audio Player PRO’ works just fine, but again, only at a level of sound quality, that the Android sound system will allow. When playing back simpler sound files such as MP3s, the user will never notice the difference.

And so, while technology seems to be moving forward, by making the technology smaller, it is also taking something away.


 

(Update 6/28/2020, 12h45: )

I suppose that I should add an observation about this product, which many readers can also infer, but that would be better stated explicitly, just because misinterpretations of the information are always possible.

Whether this USB adapter is able to give studio-quality sound, is limited by the fact that a mere 3.5mm stereo headphone jack is to be plugged into it, and that, if that headphone jack also includes a microphone pin, that mike-input is only as good, as whatever the quality of the mike is, that may or may not be included in any one headphone-set’s cord.

That mike already cannot offer studio-quality recording, and so, the inability of this USB adapter to live up to that standard, can also be seen as irrelevant from any practical perspective.

What I can tell the reader is my observation that, in spite of this, “Evolution Audio Mobile Studio” offers to sample the mike input at 96kHz, as well as, at even higher sample-rates.

What can be seen as more of an issue of fault somewhere is, that the USB adapter shown above is stated to have a Signal-to-Noise Ratio of only ~90db. This corresponds to a sample-depth of approximately 16 bits. The dynamic range is reported as being in the vicinity of ~100db, which actually exceeds a sample-depth of 16 bits.

Given that this is already in the specs, the fact follows that, if a 24-bit or a 32-bit mode could be selected, only the most significant 16 of those bits will actually be accurate. So, for the manufacturer to state, that 32-bit sample-depth is supported, creates an inconsistency within the technical specifications already.


 

And, if the user really wanted studio-quality recording ability, there also exist manufacturers today, who can supply that – at the corresponding price-tag.

Dirk

 

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