And now for something totally different. This review caused me some consternation with deciding into which category to place it. The USB Disruptor is a an example of USB clean-up tools that are increasing common as people learn of the issues that commonly plague USB audio and look for solutions to these problems. The market has seen an explosion of USB tools from the likes of the Audioquest jitterbug and Hifimediy USB isolator at the low end, the Schiit wyrd and ifi ipurifier in the middle ground, and the Jcat and Uptone Audio offerings at the upper reaches of the group. Some offer to clean up power only, others offer reclocking of the USB signal.
Before diving into the USB Disruptor itself, lets cover some background territory as this seems to be a topic of some confusion.
Why do we need USB cleanup? Doesn’t USB Support error control?
This is the first and most common misconception. USB Data that is not time dependent does support error checking and correction. USB Audio and time dependent data (streams) do not support error checking as the system does not support resequencing in the receive buffer. Time dependent USB transfer operates as a FIFO buffer and is thus considerably more susceptible to noise and other USB maladies than USB data transfers.
But USB is digital so it is not susceptible to noise like analog right?
Not quite true either. While digital is less susceptible to noise than analog, that does not mean it is impervious to it. In analog every number between 0 and 100 represents a different value so any small change caused by electrical interference results in a mis-interpretation of the data. In digital that same range of values exist but anything below an arbitrary cutoff is interpreted as zero and anything above that same cutoff is interpreted as a One. This gives digital its advantage. Noise has to be enough to cross that threshold to cause the data to be misinterpreted.
But how often does this really happen?
Common causes of electrical interference include cell phones and other wireless devices as well as Fluorescent lighting. Computer power supplies are usually built to minimal specs to save expense so power cleaning is done only to the degree it is absolutely required to make sure the computer works as expected. Since audio is not a priority for most computer manufacturers, this means that the 5 Volt line contained within USB is very often a source of noise to the data lines due to lack of line conditioning. I suggested to one user to place a fluorescent light next to their computer and run the USB cable over it between the computer and DAC and then see if they didn’t hear a difference. While this is a bit extreme, it will certainly demonstrate the lack of effective shielding in the average USB cable and possibility of passing electrical noise into the system.
How do you fix this issue?
- One way to deal with it is avoidance. Many prefer to use optical cables for data transport as optical is infinitely less susceptible to electrical noise and magnetic fields. This requires that your system have the ability to utilize optical cabling which usually is a more expensive option. Some computers come with optical support standard, many don’t.
- Another option is to clean up the power going into the system. This means UPS at the wall, a line conditioner ahead of the UPS, and a purpose built power supply with much cleaner output than standard. Again this is an option many choose, but it is not without additional costs.
- The third option is to pull the power off the USB circuit entirely so only the data is passed. This sounds easy enough but there is a catch. At first glance if the computer is powered and the USB device you are sending data to are both externally powered it seems like you should be able to only connect the pins for Data+ and data- in the USB cable and simply not pass the 5V DC over the cable. Most of the time this does not work as the PC will require the +V and -V lines be connected in order to detect the presence of a device at the remote end of the cable. So when we cut the wires for the +V and -V our device more than likely will quit working. Instead of just cutting the lines, devices like the USB Disruptor pass the signal back to the PC telling it that the device is present at the other end, but the power it passes to the device is provided by an external supply so none of the problems mentioned with typical USB power are passed into the DAC.
I tested the USB Disruptor in a number of different sets of gear and have previously owned or used the Dragonfly jitterbug, the HifimeDIY USB Isolator (both original and 2.0), ifi ipurifier3 and the Schiit Wyrd that all serve the same purpose.
My main system runs with an APC Symmetra UPS and a OneAC line conditioner between the Mains and my gear. All devices are plugged into a Marway 520-022 PDU with EMI filter. (I took the route of cleaning up the power at the wall as I ultimately found it of more benefit rather than having to find a treatment for each device separately). For purposes of the test, I bypassed my power conditioning equipment and tested all devices using nothing but an inexpensive Belkin power strip between wall and devices.
I found that the degree to which the USB Disruptor helps is inversely proportional to the degree to which the device already addresses the issues.
For Example, the USB Disruptor made a very audible difference in Schiit Audio gear that uses the Gen2 USB (modi 2 uber) but made much less of a difference when a Gen5 device was attached (Bifrost MB). Other devices varied similarly. A couple notable exceptions were devices with battery power like the ifi xDSD which seem to run off the battery even when plugged in. That nullified any difference the USB Disruptor’s change in power source might have made were the circuit fed directly from the USB line.
Perhaps most interestingly, I found that when using a separate power supply to power the Fulla2 and putting the USB Disruptor inline with the data cable, a notable improvement in the low range and better dynamics were the result. In this particular case, it seems that even when a 2nd power supply is introduced, the power provided by the primary USB line is still in play.
I found the difference to be more pronounced than those made by the Dragonfly or HifiMeDIY and about on par with the Schiit Wyrd. I find it somewhat unfair to compare the USB Disruptor to the iPurifier3 as the Disruptor makes no claim to reclock or regen the signal as the iPurifier does. I did think the iPurifier made a larger difference when paired with the Modi 2 Uber which may be partially due to power cleanup and partially due to reclocking.
The upside of the USB distruptor is that it works as advertised. The downside of the USB disruptor is the housing. The housing does not look like a professional piece of hardware and while it will likely be behind other components where it is out of sight, it could be done better. Its shape, at times, threatens to block other connectors at the back of the DAC and can be a problem on small devices. Also the stick design of the device means you need 6-7 inches of free space behind the component it is to be plugged into. For those with rack mounts or stereo cabinetry this may create a problem.
This is a tough one. The USB disruptor did exactly what it promised to do so in that regard I have to give it props. On the other hand, other models do the same thing and in some cases a bit more for the same money. I think the single biggest hurdle for the USB Disruptor is its form factor which can make it tough to fit in confined spaces and detracts from the product by simply not “looking the part”. We have grown to expect brushed aluminum shells not translucent plastic. As a side note, on a device designed to clean up noise, shouldn’t it be shielded? Bottom line, it works and it works well so if the aesthetics don’t concern you, its a good piece of kit.