Recording Audio in Windows
To test whether the USBPre is properly recording, perform the following test:
- Connect the USBPre to the computer.
- Select the USBPre as the preferred device (see Selecting the USBPre in Windows)
- Connect an audio source to an input of USBPre and select its input type via the front panel input selection buttons.
- Verify that the front panel level meters are responding to the audio.
- Launch the Windows Sound Recorder application from
Start >Programs >Accessories >Entertainment >Sound Recorder.
- Select File>Convert Now, and select 44.1/16 bit attributes.
- Record audio.
- Play back the audio to verify that it has recorded.
Input Selection
USBPre has two input channels. Depending on the recording software used, the inputs can be defined as a single, stereo input or as two separate mono inputs. Each input on the USBPre can be set to a different input types if desired.
Input Pad
Depending on the combination of microphone sensitivity and sound pressure levels, the microphone input of the USBPre can be overloaded. The bottom-side input pad inserts a 15 dB pad to scale the input gain range for high microphone input levels.
Sample Rates
Software applications control the sample rate and bit depth of the USBPre. Valid sample rates for recording with the USBPre are 32 kHz, 44.1 kHz, and 48 kHz. Valid bit depths recording with the USBPre are 8, 16, and 24 and 32 bits (32 bits is really the same as 24 bits to the operating system). Many recording applications will show many other "valid" sample rates for the USBPre. These should not be used, as the operating system performs a "sample rate conversion" while recording. The sample rate conversion is very CPU-intensive and can cause choppy audio and/or crashes.
Any sample rate from 5 to 55 kHz can be played back on the USBPre at 8 or 16 bits.
Metering
The input meter on the USBPre is calibrated in peak responding dB FS. When recording software does not have its own metering, metering the USBPre is necessary. When the red peak LED illuminates, the signal is very near clipping. Reduce the input gain control to avoid overloading the inputs.
Phantom Power
USBPre can provide phantom power for condenser microphones. When selected, 48-volt phantom power is applied to both inputs. Condenser microphones that can operate on phantom voltages from 11-52 volts will function properly with 48-volt phantom.
Dynamic microphones typically do not require phantom power. A properly connected balanced, dynamic microphone is not affected by the presence of phantom power nor will it draw any current. However, it is good practice to turn phantom power off when not needed. Poor or incorrectly wired microphone cable can cause audible artifacts in microphone signals. Some wireless receivers outputs are adversely affected by the presence of phantom power, therefore, consult the wireless receiver documentation.
Headphone Monitoring
USBPre has a high current headphone amplifier that can monitor input audio, computer audio, or a mix of both. When monitoring input audio, the audio playing in the headphones is the direct analog signal before any digital conversion has occurred and before it is sent to the computer. When monitoring PC audio the computer controls the digital audio. Note: The Windows Volume Control (controlled with the "speaker"- icon in the system tray) adjusts the level of the PC audio in the headphones and at the PC Audio output.
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