Sound Card Cables and Connectors

• Stereo Cables and Connectors
• USB Cable and Connector Pinouts

Stereo Cables and Connectors:

Standard sound cards have 3.5 mm stereo input and output jacks. Cables with 3.5 mm stereo plugs are readily available and quite inexpensive, as are adapter cables with RCA connectors on one end.

Avoid trying to add a 3.5 mm connector to a cable. These are very difficult to solder, and usually cost as much as a complete cable with connectors already attached at both ends.

If you need to connect to equipment with another type of connector, and no ready-made adapter cable can be found, your best bet is probably to buy a long cable with 3.5 mm plugs on both ends. Cut it in half, strip the cut ends as needed, and attach your chosen connectors.

However, many connectors may be difficult to attach to computer audio cables. In such cases, you can make a small adapter box or panel and install the panel-mount style of your chosen connector. Solder the cable ends directly to the back side of this connector, with the cable shield and/or ground soldered to a separate lug under the connector if needed.

Before you solder the cable, thread it through a hole in the adapter box. Make sure you use a grommet to avoid subsequent damage to the cable during use. Tie a loose knot in the cable to act as a strain relief and to prevent it from slipping back through the hole, leaving an adequate length inside the box to allow connections to be made.

The loose knot will prevent the cable from pulling out of the box, but will not protect it against twisting that could pull on the solder joints. Use a tie-wrap to anchor the cable securely to something else inside the box, or use a blob of hot-glue or silicone sealer to anchor the knot securely at the hole.

USB Cable and Connector Pinouts:

USB cables and connectors come in two different types: Type A is for connection to the computer (or smartphone, etc). Type B is for connection to a peripheral device such as a printer or USB sound card, or an Arduino or Numato board.

You may want to know the pinouts and cable colors if you are replacing the loose-fitting mini-USB socket on the 5.1 Channel CM6206 USB card, as discussed in USB Socket Replacement under Sound Card DC Input / Output Modification, as well as the "CAUTION" section of the 5.1 Channel CM6206 USB discussion under Sound Card Performance Tests. (See also the CAUTION below.)

Alternatively, you can use the +5 volt and ground pins of a standard USB port to supply modest amounts of power (100 mA max current draw). This may be used to power small external circuits such as DC Pulse Output Converters.

The simplest approach is to cut up an old USB cable. If you are just using the DC power connections, this can be an old USB 1.0 cable, such as from an old printer or other unused device. Cut off the device connector, and keep the USB connector plus as much cable as you want to connect power to your circuit. Strip the cut end of the cable, then check that the red and black wires do in fact carry +5 and ground, respectively.

CAUTION: Do not rely on the cable colors being correct! The author has personally encountered a USB cable that came with a CM6206 sound card, and had red and black reversed. It had functioned correctly because both ends were reversed; only when cut and tested was it found that +5 was black and ground was red.

Be sure to strap the cable securely to your circuit, or otherwise provide strain relief.