“The formulation of the problem is often more essential than its solution, which may be merely a matter of mathematical or experimental skill.” – Albert Einstein
Designed to standardize connection with computer peripherals, USB interface enables both communication with peripherals and supply of electric power. Communication with external sound cards (DAC) via USB interface is not really a problem and 480 Mbit/s data transfer speed in USB 2.0 standard is more than sufficient for transport of even the most complex high resolution audio files.
Powered by incredibly noisy and for computer audio completely inappropriate 5V DC, USB interface is an excellent connection for various PC peripherals like printers, external hard drives, keyboards, mouses, digital cameras etc. However, an extremely power sensitive D/A converter shouldn’t be connected to, or even worse powered by 5V generated from motherboard’s switching power supplies. Tragically, some USB converters cannot even be recognized by computer, if 5V from motherboard failed to reach their USB receiver.
High quality USB D/A converters require high quality USB port
The problem of high end audio gear connection was not considered during development of USB industry standard and therefore optimal conditions for this type of peripherals cannot be expected. Furthermore, connecting of other USB devices to the computer used for audio transport, particularly USB disks or even a mouse can seriously affect the quality of audio playback. High quality USB D/A converters require high quality USB port, separated from other USB devices, dedicated to audio transport only and there is, unfortunately, no such a thing on computer motherboards.
While other audio companies were busy improving their USB D/A converters, South Korean company SOtM (Soul of the Music) asserted the problem on computer side and the solution practically jumped out.
SOtM tx-USBexp Audiophile PCIe to USB 3.0 card is basically a high end USB port, connected to computer’s motherboard via Peripheral Component Interconnect Express or simply PCIe slot on computer’s motherboard. The card has an ultra low-noise voltage regulator, ultra low jitter clock and can be powered externally with linear PSU or battery. There is also a switch for complete disruption of DC 5V from PC. Simple, elegant and absolutely necessary for high end computer audio transport, SOtM card serves exclusively for connection of USB D/A converters and every single USB DAC connected to PC via SOtM tx USB card will instantly sound better.
Consequently, laptops, Mac Mini, NUC, Raspberry Pi and similar constructions are definitely not able to serve as a State-of-the-Art
computer audio transport.
SotM tx-USBexp card is an ideal link between computer’s motherboard and USB DAC. Therefore, a desktop computer with motherboard that allows connection of at least one PCIe card should be considered as a minimum for a serious computer audio transport. Consequently, laptops, Mac Mini, NUC, Raspberry Pi and similar constructions are definitely not able to serve as a State-of-the-Art computer audio transport.
SOtM card can be swiftly connected to PCIe slot, no experts are required for a really simple installation procedure and only one screw on the back panel of your desktop computer should be tightened.
SOtM USB card can and should always be powered externally, with an appropriate linear PSU or a battery. SOtM recommends the use of a specially developed mBPS-d2s battery power supply for this purpose. We have tested SOtM card with several linear PS units and found out that a non regulated PSU DC 8V works perfect.
Providing clean, noise free power to SOtM USB card makes a real harmonic fireworks. The sound becomes even more involving and completely lifelike. Timbre of acoustic instruments, especially on excellent DSD recordings, is unimaginably sweet and has “organic” character. Actually, there is no going back once you become addicted to sound of externally powered SOtM tx-USBexp card.
Computer audio transport via USB interface is simply not possible without SOtM tx-USBexp card, if a true high fidelity is required.
To make a long story short, computer audio transport via USB interface is simply not possible without SOtM tx-USBexp card, if a true high fidelity is required. A desktop computer with SOtM card is an absolute must for everyone interested in computer audio transport of highest quality. If you enjoy recordings of classical music on period instruments, exceptional DSD recordings of large symphonic orchestra or amazingly recorded, subtle details of jazz trios, a fanless, desktop PC with externally powered SOtM tx USB card is a condicio sine qua non for your future computer audio transport. SOtM card link.
you had done great job! thank you for the good article!
I understand that it is probably made in small batches but – don’t get me wrong – the price is way over budget of normal man. I have built already one system based on previous version of APLinux and result wasn’t best despite planning it for a year and spending 1200 euros on hardware. Now would like to build new one with just 400 euros so only usb card for 350 is beyond my limit. I would rather invest in the double power supply – one solely for motherboard and other for usb/ssd etc. That makes more sense and is economically wise.
Anyway thanks for info. This was very educational after all.
Also would like to thanks for APL – great job guys!
Regards – Pawel
Which computer components do you have for 400 euros?
This 400 euros was the absolute minimum and I have exceed this over 100 euros so far. This is what I have bought until now (ebay and amazon):
Nox Media HTPC case – 50 euros
Asrock Q1900M motherboard with processor – 79 euros
Corsair CMX8GX3M2A 1333mhz C9 2x4Gb ram – 72 euros
ESI Juli@ sound card – 148 euros
Seasonic platinum 400FL psu – 138 euros
Kingston SSDNow V300 60Gb – 44 euros
Total 531 euros
There could be some savings particulary on the psu and ram but I am buying strictly one thing in the month so was abble to get something more expensive, Also this server is for my son and he needs something that could play other media (BD) so I decided to give him as much room for upgrade as possible.
Hope this explained my opinion and did not offend anybody.
Best regards – Pawel
Thank you for answer. I want to buy Asus Xonar Essence STX, but ESI Juli is also good.
I was thinking along similar lines, same mainboard (though the ASRock type without the M) and components.
The ESI Julia is really a very good choice (I have one in a different setup): even John Westlake of Audiolab M-DAC and other products fame, is impressed with it! If it would do native DSD, I wouldn’t need anything else.
I agree with your comments on pricing. Instead of using the SotM card you may want to consider the Audioquest Jitterbug. For 50eur, a no-brainer.
A further step may be to use a USB DAC that isolates the USB port galvanically from the DAC circuits, such as the Denon DA300USB; many other new DACs use the same trick (but in different ways). iFi Dacs use nifty tech to clean-up the USB signals and are still affordable.
But it is best to treat the problem at the source as with the SotM card. I’ll guess we will see more of these products in the market place but hopefully at more realistic pricing.
USB ports on standard mainboards are getting better than they used to be, anyway. With more stable power supplies, RF and EM shielding and even static charge protection. So there are choices!
Good luck, Pawel. Best, marco
I’d like to understand why the solution of an optical connection like spdif toslink is not the better one. I plan to buy a raspberry pi whith digipi card to send an optical signal to the dac and avoid the usb issues. Cost less than 100 €
Because of spdif limitations to 24/192kHz. You can’t listen to DSD for example.
I would argue with need to have all music in DSD. I have spent a lot on my collection of music from 70′ and 80′ and replacing all my cds for much more just to have the same music seems to be not wise (since it is recorded from the same source tape). Some would say that it was remastered but the effect of this is not always good. In my experience most of the time it is worst indeed.
Anyway aside my opinion on the existing music I agree that we need better sound quality and DSD looks very promising. The only trouble is that prices are sky high for equipment. At least beyond my budget. In this connection I have turn my attention to the DIY and found some interesting kits from http://www.twistedpearaudio.com/digital/buffalose.aspx
I could house it in the box of my choice or even put it shielded inside pc with internal usb connection (there is enough space for hamster family inside). Beside good price the possibility to build it my own way does tempt.
So now there is my question:
is there any chance to have it tested the same way as other equipment you did in the past?
I know you are busy and perhaps have better things to do but there is always worth to ask, right?
For my music server based on your APL 3.1 – it is already completed and works perfect. The temperature never exceeds 42 degrees and ESI Juli@ does not have any troubles playing my music. I have been even able to make my Jolla phone to perfectly manage MPD using SMPC.
Thank you for your great job and wish you all a very happy new year!
Best regards – Pawel
I would agree with you that some remastered DSD’s are worst than original PCM files.
You can find many poor DSD’s that can’t be called DSD’s at all. Some of manufacturers
just take PCM files and convert them to DSD format and they think it’s DSD. It’s not.
After listening many DSD’s, all PCM music to me feels artificial now. I don’t want to
listen it any more, so there is no point to test anything.
What non regulated PSU DC 8V was used in the review?
This is a urban legend imho.
A digital signal can’t be affected except :
– during transcoding (latency, EM artefacts, noise)
– during DA conversion
– during transport (over USB, etc) the only thing that can happen is loosing some bits because of a bad cable/connector (or big EM impulsion caused by a nearby nuclear explosion) : latency on the USB bus will be handled by buffering on the DAC side.
So as long as the DAC is external, and the USB cable is good : anything bad you notice on the signal happens whether during encoding or on the analog path.
Just my 2 cents
I’m thinking about getting one of these even though I’m not sure it’ll help anything, I’m confused about the external power supply. what is the polarity of this power input? It’s not listed anywhere I can find and I’d hate to destroy the the thing before I can determine if it works or not. What is the polarity of the 8V adapter you used? Thanks
For that price I’ll go with a good audio card that outputs analogue and digital. Sometimes simpler is better.