## There do in fact exist detailed specs about the Scarlett Focusrite 2i2.

One fact which I have written about before, is that I own a Scarlett Focusrite 2i2 USB-sound-device, and that I have tested whether it can be made to work on several platforms not considered standard, such as under Linux, with the JACK sound daemon, and under Android.

One fact which has reassured me, is that The company Web-site does in fact publish full specifications for it by now.

One conclusion which I can reach from this, is that the idea of setting my Linux software to a sample-rate of 192kHz, was simply a false memory. According to my own, earlier blog entry, I only noticed a top sample-rate of 96kHz at the time. And, my Android software only offered me a top sample-rate of 48kHz with this device.

The official specs state that its analog input frequency-response is a very high-quality version of 20Hz-20kHz, while its conversion is stated at 96kHz. What this implies is that when set to output audio at 44.1 or 48kHz, it must apply its own internal down-sampling, i.e. a digital low-pass filter, while at 88.2 or 96kHz, it must be applying the same analog filter, but not down-sampling its digital stream.

And so, whether we should be using it to record at 96kHz or at 48kHz, may depend on whether we think that our audio software will perform down-sampling using higher-quality filters than its internal processing does. But there can be an opposite point of view on that.

Just as some uses of computers see work offloaded from the main CPU, to external acceleration hardware, we could just as easily decide that the processing power built-in to this external sound device, can ease the workload on our CPU. After all, just because I got no buffer underruns during a simple test, does not imply necessarily, that I would get no sound drop-outs, if I was running a complex audio project in real-time.

Dirk

(Edit 03/21/207 : )

## Testing the Focusrite Scarlett 2i2 external sound device, with my Samsung Tab S Tablet

I have tested, whether this external USB recording tool, works with my Samsung Galaxy Tab S Tablet, using a ‘StarTech.com’ OTG adapter. The results were resoundingly affirmative.

In This Earlier Posting, I had tested the same USB Sound Card, with my Samsung Galaxy S6 Smart-Phone. At that time, an attempt also to use it with my Tab S tablet had failed. In order to get the Scarlett 2i2 to work with the Tab S, the following two conditions need to be fulfilled:

1. The amount of current that the USB Slave Device may draw, needs to be reinforced, in principle, with a self-powered OTG adapter, or with a similar arrangement. The ‘StarTech.com’ is Not a self-powered OTG adapter, and with it, the Scarlett 2i2 is bound to draw too much current, for the likes of the Tab S. It was after all meant as an audio workstation workhorse, and not as a replacement for a simple USB Microphone.
2. The Master / Host Device, the Tab S, needs to have the correct drivers.

Condition (1) is something I was able to fulfill for now, in a roundabout way. I bought a ‘j5create USB 3.0 4-Ports Mini HUB’, with the part number ‘JUH340′. This is a self-powered hub by default, with its own power cord, and has Type A USB connectors up-stream and down-stream. Granted, it has a special up-stream cable, that connects to the hub with a special connector, just so that the user does not get this socket confused with the down-stream sockets. But then, the far side of that cable has a standard Type A USB jack.

This USB jack can be plugged, into the far side of the OTG adapter. Since the hub is self-powered, the current requirements of the Scarlett 2i2 are met by it, and not by the OTG adapter, and thus not by the micro-USB port on the Tab S, the latter of which now faces a minimum current load.

## Testing the Focusrite Scarlett 2i2 external sound device, with my Samsung S6 Smart-Phone

I have tested, whether this external USB recording tool, works with my Samsung Galaxy S6 Smart-Phone, using an ‘StarTech.com’ OTG adapter. The results were mixed. In An Earlier Posting, I had tested whether this external USB Sound Card, works under Linux. And the answer to that question was a resounding Yes.

When we plug an OTG adapter into a smart-phone or tablet, this puts the mobile device into Master / Host Mode, that would otherwise normally work in Slave Mode. Thus, we can then plug in a USB storage device, and hopefully have that recognized, while by default, we can only plug our mobile device into a computer, and have the computer recognize this mobile device, as the storage device.

But it is also plausible to connect other external devices to our mobile device, when using an OTG adapter. All this happens because the OTG adapter itself contains an additional chip, that gives it the ability to act as a USB Host. Whether such external devices will work or not, generally depends on two factors:

1. Whether the micro-USB port on the mobile device can output enough current, to supply the external / Slave device, and
2. Whether the mobile device possesses the drivers needed, for the USB device in question. Under Linux, this last question is more likely to be answered in the affirmative.

The OTG adapter I was using, uses its micro-USB side as the only power-supply. This means that if the connected device draws a full 500mA of supply current, we are pushing the limit, that is generally set for USB 2.0  PC ports.

## Testing of USB Sound Device Complete.

According to my previous posting, I needed to do a more thorough test of the USB Sound Card I have bought, which is a “Focusrite Scarlett 2i2“.

In particular, I needed to address the discrepancy according to which, the Linux JACK daemon reports capture at 32 bits, while the specifications of the sound card state a 24 bit sample format.

Also, I needed to be sure whether it would run as well at 96 kHz, as it already did at 48 kHz.

According to my more complete test, the 32-bit sample-format which ‘QJackCtl‘ shows me, which can be viewed in its Messages box, state the ALSA parameters and not the JACK internals. Therefore, JACK has after all chosen to capture and/or play back audio at a physical 32 bits, at the 96 kHz sample-rate. This is not, after all, a statement of the JACK internal behavior.

Since I am using Linux, and since the manufacturer chose to rate this capture device as only being capable of 24-bit capture, I must assume that for hardware reasons the device uses 32-bit registers, but that only the first, most-significant 24 of those bits are accurate. Therefore, when I open ‘QTractor‘ – the Digital Audio Workstation / Tracker application, it is best to truncate its capture format to 24 bits as well, which is most probably what the Windows or Mac drivers for this device do.

Aside from that, using QTractor next, to capture a 96 kHz, 24-bit, stereo FLAC file was easy and uneventful. Further, the stability of my software suggests that I can play with the GUIs as much as I need to, to figure them out, and I will not screw anything up.

After I closed JACK, I next imported this FLAC file, that plays for 14 seconds, into “Audacity“, which has been set up to use the default sound settings (‘PulseAudio‘), and which performs an on-demand re-sampling of the FLAC file.

The on-demand FLAC playback is not filtered well by Audacity, but since it is running at 96 kHz, compared with the 44.1 kHz that the internal sound of the laptop runs at, this observation is not surprising.

And then the captured sound clip simply contains, what I spoke into my microphone.

Dirk