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EPOS|Sennheiser GSX 300 External USB Sound Card (updated for confusing corporate reasons)
4.4Overall Score
Name: EPOS GSX 300 External USB Sound Card
Price (RRP): $129.90
Manufacturer: Sennheiser

The EPOS|Sennheiser GSX 300 External USB Sound Card is from the new EPOS gaming brand. It is a little device, intended to improve on your computer’s audio performance. And an improvement in sound quality is most certainly something most computers can benefit from.

Review: EPOS|Sennheiser GSX 300 External USB Sound Card

  • Australian Website here.
  • Manual and fact sheets towards bottom of pagehere.
  • Price: A$129.90 – seen for $119.95 online.
  • From: Legitimate retailers and a direct from EPOS.
  • Warranty: Two years
  • Country of Manufacture: China
  • About: EPOS is owned by Sennheiser, a German company famous in the field of both headphones and microphonessomething. It turns out that EPOS and Sennheiser are owned by another entity, Demant A/S, and operate independently. Some gaming product lines that were Sennheiser are now EPOS. Determined to keep things confusing, it seems that even though EPOS is an independent business, at least some products are to be referred to as EPOS|Sennheiser. Including the GSX 300. If you see EPOS GSX 300 at points in this review, please read it as EPOS|Sennheiser GSX 300.

About the GSX 300 External USB Sound Card

The GSX 300 External USB Sound Card is a neat little device, less than 100mm on its longest dimension. You plug it into a USB port on your computer and it will become a DAC and ADC – Digital to Analogue converter and Analogue to Digital converter. On the back are two 3.5mm sockets, one for a microphone and one for headphones. Or, of course, the two of them together for a gaming headset. Also on the back is a Micro-B USB socket. You plug this into a computer with the supplied cable, the other end of which has a standard USB Type-A plug.

On the front is a large level control with an illuminated ring around it and one single control button. Using the EPOS Gaming Suite software on your computer, you can adjust the EQ of the output and input both. You can switch between straight two-channel playback and simulated 7.1 channels. On the microphone side, you can control noise cancellation, set a noise gate and set the character of voice to standard, “warm” or “clear”.


The unit is powered via the USB connection, so there’s no wall wart. All in all, it’s a neat package.

The GSX 300 External USB Sound Card is fairly light on for formal specifications. All it says is that 24-bit, 96kHz sampling is supported, along with 16-bit, 48kHz in 7.1 channels “with EPOS Gaming Suite”. And that the recommended headphone impedance is 25 to 75 ohms.

In addition to the black unit, there’s a white “Snow Edition”.

Setting up the EPOS GSX 300 External USB Sound Card

It’s hard to see how it could be easier to set up a sound card. No drivers are required on Windows 10 or Macs. I don’t have a computer with an earlier version of Windows so I couldn’t check for USB Class 1.0 Audio compatibility. But it certainly installed easily on both Windows 10 and Mac with no particular settings changes.

When I first installed it on Windows 10, Windows reported that the EPOS |Sennheiser GSX 300 External USB Sound Card supported 16- and 24-bit audio at 48kHz and 24-bit audio at 96kHz sampling. Full stop. CD-standard 44.1kHz wasn’t listed. Later, after I’d upgraded the unit’s firmware to version 60, the Windows audio control panel was locked at 16 bits and 48kHz. But on a Mac the original options were still available. Go figure.

As we’ll see when I get all nerdy later on, the hardware actually supports a much wider range of sampling rates. EPOS is promising higher sampling rates in the future for 7.1 channel audio, so clearly the firmware is still a work in progress.

In addition to allowing the adjustments mentioned above, the EPOS Gaming Suite also manages the unit’s firmware.

An upgrade wrinkle

I used the GSX 300 for a couple of weeks without bothering with the Suite. Which was probably just as well, because when I did install the suite and let it have its head with the firmware update, it hung part was through. Since the installation panel insisted that I “not remove device or close Gaming Suite”, I was kind of stuck. The progress bar indicated that it was maybe fifteen percent of the way through, and nothing was happening. I let it be for a couple of hours, but eventually I just pulled the USB cable to see if perhaps it had completed. It hadn’t. The unit was semi-bricked.

Semi-bricked? The hardware was fine and it still worked as a DAC and an ADC, but it had amnesia. It no long had the manufacturer name of Sennheiser and product name of “EPOS GSX 300”. It was now Conexant and “Hi Res USB-C AUDIO”. The front ring no longer illuminated, and the volume control had no effect.


I contacted the EPOS people and it turns out they had a small app to re-install the firmware. This worked perfectly, installing version 59. The EPOS Gaming Suite wanted to upgrade it to version 60. I let it go and this time it worked perfectly, upgrading the thing in just a few seconds. Unplug and re-plug and it was now working perfectly on version 60.

Let’s go super nerdy

So? Why do I bother to relate all this? Because that Hi Res USB-C AUDIO interlude gave a rare window to peer more deeply into the hardware. While it was in that state, Windows reported that the EPOS GSX 300 now supported 16-and 24-bit audio all the way from 44.1kHz to 192kHz sampling. Not quite trusting this, I ran a frequency response test using 192kHz sampling. Yes, it was definitely sampling at that, with the output frequency response extending to 85kHz! It was weird, though. The shape of the high frequency adhered to three different curves for no particular reason I could discern. The best curve had the output down by just over 0.5dB at 85kHz, the worst at 2.5dB at 85kHz.

Clearly the EPOS GSX 300 External USB Sound Card is capable of far more performance than is currently enabled in the unit’s firmware. Perhaps we’ll see that realised at some point.