USB allows us to power 5 volt devices with between 100mA and 500mA. The big question is, does my particular DAC (or USB Converter) need that 5 volt connection? It's a good question since some DACs do require it and some do not. We supply USB cables in two different formats:
1. Data Only: three wires, two data and one ground, no 5 volt power.
2. Standard: four wires, two data, one 5 volt and one ground wire.
The choice is simple if you already know that your DAC does not require a 5 volt wire to power it. You would get the 'Data Only' USB cable. If you don't know, then we'll describe below a rather convenient method of finding out.
If you know or determine that your DAC requires 5 volt power to function (or at least handshake), then you should get the 'Standard' USB cable and be done with it. It has a shielded 5 volt (Vbus) wire to power your DAC or USB Converter from your computer.
The first way to find out whether your DAC needs 5 volts might be to look on your DAC or device manufacturer's Web page, or email them with this question. Or perform a simple do-it-yourself test. Cut a slim piece of tape that is about 1mm wide and about 6mm long. We prefer masking tape, you know, the standard beige colored tape or the blue painter's tape. You want something that is rather strong but won't leave any sticky residue on your USB connector pins. Pick any USB cable for this experiment.
Stick one end of the tape sliver into the USB connector over the pin that carries the 5 volts. This is pin #1 (Vbus) in the following pinout diagram. You can easily apply the tape on the A side connector. Then fold the tape sliver over the bottom edge of the connector, and press firmly in place. This will allow you to insert the connector into your computer USB port and the tape should cover the 5 volt pin, thus disconnecting the power connection. This is harmless, and even if you get the pins mixed up at first, there isn't any harm done. To insure that you get a good test though, study the pinout diagram and carefully apply the thin slice of tape to the correct pin at position #1.
Once you have applied the tape and plugged the cable in, you can turn on your computer and DAC to see if the DAC is recognized by your computer. If the DAC and your computer establish a connection, then you should be able to go with the 'Data Only' cable. To be sure, play some of your favorite music.
If after a few recycles of power on the DAC, you do not get the DAC to be recognized by the computer, you can deduce that your DAC or USB Converter device requires a 5 volt power source.
A.) If your computer recognizes your DAC with the 5 Volt lead blocked, choose the Data Only cable.
B.) If your computer does not recognize the DAC with the 5 Volt lead blocked, you should choose the Standard cable.
These simple procedures will enable you to pick the right USB cable for your current computer audio setup. There is one other possible scenario, however. Some DACs only require 5 volts to be present for the devices to perform an initial handshake. This is the startup procedure that USB uses on the host to signal the endpoint and establish a few handshake packets. Once the DAC is recognized, power is no longer needed. Some USB cards and some music servers provide a switch to turn off the 5 volt power coming out of the computer once connection is established. If this is the case with your gear, your documentation or user manual should spell this out. The right cable for this would likely be the 'Standard' cable which has a 5 volt lead.