SOtM tX-USBexp Audiophile PCIe to USB Audio Card and mBPS-d2s Intelligent Battery Power Supply

SOtM tX-USBexp Audiophile PCI to USB Audio Card
Device Type: PCIe to USB Audio Card
Input: barrel power input jack, 4-pin IDE power connector
Output: 1x USB 2.0
Dimensions (H x W x D): comes with short and long PCI trim plate
Availability: Through Authorized Dealers
Price: $350.00

mBPS-d2s Intelligent Battery Power Supply
Device Type: Battery Power Supply
Input: barrel power connector
Output: barrel power connector
Dimensions (H x W x D): 53mm x 105mm x 150mm
Availability: Through Authorized Dealers
Price: $400.00

US Distributor's Website:

SOtM "Soul Of the Music" PCIe to USB 3.0 Audio Card
The final SOtM component to get our attention is their PCIe (Peripheral Component Interconnect Express) to USB 3.0 Audio Card. Who needs one? I'd say anyone with a PC who wants to get the best out of their USB audio. That's who.

The SOtM tX-USBexp Audiophile PCIe to USB Audio Card
The SOtM PCIe to USB 3.0 Card is compatible with Windows 7/8 and Linux. You can power the SOtM card in three ways; through the 4-pin IDE connector that uses your computer's dirty power, externally using a 9V power supply (like the one that came with your cell phone), or with a high quality linear battery-power supply like the SOtM mBPS-d2s Intelligent Battery Power Supply which I'll also be talking about in this review.

The SOtM card "...has a unique design incorporating a new and improved ULNR (ultra low noise regulator) for digital signalling, clock and USB power circuitry. It has power input noise filters, PCI Express slot noise filters, an extremely low jitter clock and an active noise canceller for clock power." You can see a number of Samyoung NHX electrolytic capacitors standing up on the SOtM's board next to a couple of Elna capacitors and some black aluminum heat sinks to keep everything cool. Basically all this means the SOtM card takes care in regulating and filtering the power powering it so it doesn't pass along any nasty noise to your DAC. There's also a switch on the card that turns the power to the attached USB cable on or off so if your DAC does not need power from the USB bus you can turn it off at the source.

In terms of physical installation, you just need to open your PC (with the power off and disconnected) and slide the SOtM Card into an empty PCI express slot (if you don't have a PCI express slot in your PC, SOtM also offers the tX-USB regular old PCI to USB card). The card comes with full-size and low-profile PCI back plates. On the software side, you need to install the SOtM tX-USBexp Windows driver which is included on disc with the card and is also available from the SOtM website's support page. I downloaded the latest driver (v1.16.3) and had no issues with setup using the SOtM card running JRiver Media Center with the SOtM Copper USB cable mainly connected to the Auralic Vega DAC. The Vega was in turn connected to my Pass INT-30A amp which was driving my DeVore Fidelity The Nines.

mBPS-d2s Intelligent Battery Power Supply
The mBPS-d2s houses two batteries. While one battery provides power, the other charges and the mBPS-d2s switches between these functions automatically. So all you ever have to do is plug it in and connect it to the device you want to power. There are a series of pairs of LEDs on the unit's front side showing output status, charge status, and "low bat" status. The unit is powered with an included external 9V supply that plugs into your wall outlet.

Listening to a PCIe to USB Card
Listening to a PCIe to USB card is easy. Or I should say comparing the SOtM PCIe to USB card to my PC's crappy integrated USB output was easy. A) listen, swap to B) listen some more. There was literally no contest between the two. The SOtM card was able to pull more musical information out of my PC as compared to the internal USB port. Music was at once more concise, more textured, more tonally colored, and more resolute with a bigger sound picture that was much easier to follow individual instruments within. In other words, the SOtM PCIe to USB card is all good.

I listened to a host of albums using the SOtM card including all five of last week's Download(s) of the Week (see review), a few DSD selections including Nat "King" Cole and Mahler, and various and sundry favorites and the music was all well served by the SOtM's cleaner, more precise, and more naturally colorful bigger sound. Switching back to my PC's USB output was a sonic let down having a good chunk of your music's goodness taken away and swallowed up by your PC's noisy insides.

Do I really need to say more? Well there is the price of the SOtM card and at $350 its certainly not cheap. So we have to ask ourselves, is the SOtM worth the dough? Since I don't have another PCIe to USB audio card here to compare to the SOtM, I'll have to extrapolate based on other factors. Namely, the degree to which the SOtM offers an improvement over my PC's internal USB port which is nothing short of dramatic. It is demonstrably and utterly obviously better. No ifs, ands, or buts about it. Its worth mentioning that if you have a DAC that accepts S/PDIF inputs, you could also get an external USB-S/PDIF converter for the same money or less than the SOtM USB card that can also effectively isolate your DAC from your computer's internal noise (see USB - S/PDIF Converter reviews).

I powered the SOtM card with an external power supply (from an old cell phone) plugged directly into my Wiremold outlet strip as well as with SOtM's mBPS-d2s Intelligent Battery Power Supply. The audible differences between these two powering methods were not as dramatic as those differences noted between the SOtM card and my PC's internal USB output but there was still a noticeable improvement mainly in low-level detail retrieval. Using the SOtM battery power supply, the apparent noise floor was reduced making things like dynamic contrasts more distinct and there was also a more relaxed presentation overall as if sounds were coming from a quieter place. I also heard improved bass performance in terms of a more solid and focused sound image. Bass was in a word bigger and tighter.

How Much Is Clearly Better Worth?
Assessing value is a tricky thing. I would say in general that your main system components should get the lion's share of your hi-fi budget with some left over for necessary things like cables, a decent rack, and room treatments where possible. If you've invested in the neighborhood of 4-figures in a USB DAC and you are running it from a PC, and the rest of your system is adequately sussed, i.e. you enjoy listening to it, I would say that when you come across a spare $350 you would be hard-pressed to find a better investment in your PC-based playback than the SOtM tX-USBexp PCIe to USB card. It provides a greater level of improvement than any USB cable I've heard, for just one example, and it costs less than a lot of them.

The mBPS-d2s Intelligent Battery Power Supply is a tougher sell seeing as its sonic benefits were not as dramatic. Again, how much you have invested in your system is typically a good gauge in determining the value of incremental improvements that are provided by accessories like the SOtM battery power supply so if you have a very resolving system already, I'm confident you'll not only hear but appreciate the benefits of battery power.

Associated Equipment

jky999's picture

How would this configuration compare to the SOtM SMS-1000 ignoring the price difference?  Actually, if my understanding is correct, the SMS-1000 might be the better deal since it eliminates the need for a dedicated music computer.

Michael Lavorgna's picture

...outperformed my PC with the SOtM card (as well as my MacBook Pro) so ignoring the price difference makes this an easy choice - the SOtM server wins. And you are right, with the SOtM server you do not need a computer to rip CDs or play music. You do need either a smartphone or tablet for use as a remote.

christopher3393's picture

""There's also a switch on the card that turns the power to the attached USB cable on or off so if your DAC does not need power from the USB bus you can turn it off at the source."

Thanks for this recommendation, Michael. Since the Vega does not need 5V power from the USB, did you turn the switch off? I'm also wondering if switching the power off decreases the need for the battery PSU. And, of course wondering to myself how this solution compares to the iFi iUSB solution, which I use with the Vega and a cable much like the iFi Gemini (Kingwin uArt). My pc definitely needs some help.Because of space limitations, I'm trying to avoid having to add a dedicated music server along with a full functioning pc, which I need to have in this space. Hoping that maybe the SOtM card along with a couple of SOtM SATA filters and maybe a SOtM fan filter might provide a nice compromise.

Michael Lavorgna's picture

...but did not notice a significant difference. I hadn't thought of the iFi iUSBPower device but that would make for an interesting comparison since they attack similar issues in different ways.

Larry007's picture

Would be interesting to get a shootout between the SOTM card and the cheaper PPA Studio USB card (120 $) together with the 5V Bakoon BPS-02 battery PSU. Also JPlay is close to make their own USB card, that will have a price around the same as the SoTM card. So 3 different cards to choose from next year, nice. Also sata cables should be important, we know you are fearless Michael, give us a sata cable test soon smiley.        

Priaptor's picture

is that Pang's card is better.  I am using Red Wine's Black Lightening battery power supply for 5v and 12 for the Zuma.

Pang's card is 1/2 the price and IMO better.  Look around on JPlay forum I think many feel the same.

As you, I await the JCAT product.

Michael Lavorgna's picture a very nice way of putting it ;-)

Steven Plaskin's picture

The 5V Bakoon BPS-02 battery has been a big disappointment. I have been unable to get it to work with a number of DACs including the Wavelength Crimson. To put it another way, the only DAC I have been able to use it with was the Calyx Audio Femto; a DAC that does not depend on a constant 5v supply from the computer. The folks at Bakoon have been unable to offer a solution or work around.

Larry007's picture

Sorry to hear that Steven. The Bakoon BPS-02 only gives 5V 1A, my Calyx 24/192 DAC needs 5V 2A, so maybe true that a number of DACs cant use it. But for the Paul Pang PPA USB card, 5V 1A is fine. I have not got a Bakoon myself, but it´s difficult to find an alternative battery PSU with a dual construction. SOTM mBPS-d2s output 6.5- 8.4V in 1.5A as far as I know, not sure which DACs it can work with either. But I would love to find one or two more 5V battery PSU, that doesn´t cost you an arm.          

Azteca X's picture

Thanks for reviewing this in particular, Michael.  I am building a C.A.P.S. soon ( and the main difference between Topanga and Lagoon is the SOtM USB card.  Glad to hear someone with good ears and good gear can definitely tell the difference.  I'll have to look into the return policy but it seems like a promising buy somewhere down the road.

bearcatsandor's picture

What makes this a soundcard as the aiticle title suggests?  Isn't it just a usb 3 port on a pcie card with the ability to provide your own power supply?

Michael Lavorgna's picture

...are typically the name of the product as defined by the manufacturer which is the case here. I would note that they do not call the SOtM a "soundcard", they call it an "Audio Card". The word "soundcard" does not appear anywhere in this review including the article's title.

DavidZ's picture

Mike -- I've been listening to the SOTM card in my Zuma for a couple of months now, and I agree with your observations. I haven't tried the Paul Pang card yet (one is actually sitting in my closet, awaiting my next urge to tweak). I will say, along with Priaptor's comments, the Black Lightning really ups the game of both the Zuma and the SOTM Card, which will take an external 9v lead from the Black Lightning -- a serious, profound upgrade,IMHO.

One final note: Windows 8 already has the correct driver for the SOTM -- it doesn't need one loaded. -- David

WhoDAC's picture

$350 is a hard pill to swallow for this in my opinion. One can add a linear power supply to the USB cable with a product from iFi ($200) or AQVOX ($150). I have also read on several boards of this card having driver issues.

Pocketempty's picture

Haven’t had any driver related issues with Windows 10.

jason spark's picture

Got a good deal from I must say it's one of the best interfaces I had. Latency won't be an issue as well.

Paul Davis's picture

The only possible justification for this device is if you insist on using USB to power your DAC, which is pretty stupid to do in the first place.

Rule #1 of digital data: if it starts out as a given pattern of bits, and ever ever changes even a single bit without you asking it to, then the device or cable or connector is faulty. Not "colored" or "full" or "detailed" or "noisy" but ... faulty.