SoundCheck Technical Support Note

Balanced Sound Card Calibration Connections 1

450 Harrison Ave, Suite 307 - Boston, MA 02118 - PH 617-556-4104 - Fax 617-556-4145 - www.listeninc.com

Balanced Sound Card Calibration Connections

When calibrating a sound card with Balanced inputs and outputs it is important to follow the wiring procedure noted in Figure: 1-1 Balanced Sound Card Calibration Connection.

Figure: 1-1 Balanced Sound Card Calibration Connection

For the purpose of calibration, do not connect the ground of the XLR connectors. Leave them “Floating”. (NC = Not Connected)

Do not short the Low (-) of a balanced output to ground. With some Active Output devices this will result in distortion on the High (+) signal.

(The low (-) of the balanced input can be tied to ground. Shorting the low input insures that it is not a source of noise and usually causes no problem.)

Note: When a sound card is calibrated for Balanced mode but used in Single-ended mode, there will be a 6 dB drop in the output level. Only one line of the balanced output is being used. See Figure: 1-4 Balanced Output to Single-ended Input.

When calibrating and/or using a Balanced Sound Card in Single-ended mode it is important to follow the guidelines outlined in the following section.

+-

NC

Sound Card Balanced Output(to Meter)

DMMset to

Volts AC

+ -

+-

NC

Sound Card Balanced Input(from Meter)

SoundCheck Technical Support Note

Balanced Sound Card Calibration Connections 2

450 Harrison Ave, Suite 307 - Boston, MA 02118 - PH 617-556-4104 - Fax 617-556-4145 - www.listeninc.com

Balanced vs Single-ended ConnectionsSingle-ended or Unbalanced outputs can typically be connected to Balanced inputs in either of the two methods shown in Figure: 1-2 Single-ended Output to Balanced Input 1 and Figure: 1-3 Single-ended Output to Balanced Input 2.

Figure: 1-2 Single-ended Output to Balanced Input 1

Figure: 1-3 Single-ended Output to Balanced Input 2

Balanced output to Single-ended input wiring is a different matter. It is important to not short the Low (-) of a balanced output to ground. With some devices with Active Balanced Outputs this will result in distortion on the High (+) signal. (Transformer balanced outputs can have the low connected to ground.)

Figure: 1-4 Balanced Output to Single-ended Input shows the suggested wiring for connecting a Balanced output to a Single-ended input. The measured level at the single-ended input is down by 6 dB since only one line of the Balanced output it used.

Figure: 1-4 Balanced Output to Single-ended Input

Note: (NC = Not Connected)

0 dB is measured at the Balanced Input

With the output level of the Single-ended Output device set to 0 dB,

RCA or¼" Phone XLR+

-+

Single-Ended output to Balanced input

cable

0 dB is measured at the Balanced Input

With the output level of the Single-ended Output device set to 0 dB,

RCA or¼" Phone XLRcable+

-+

Single-Ended output to Balanced input

NC

-6 dB is measured at the single-ended input

With the output level of the Balanced Output device set to 0 dB,

RCA or¼" Phone

XLR cable

NC

Balanced output to Single-Ended input

++-