Data AcQuisition And Real-Time AnalysisScope - Spectrum - Spectrogram - Signal Generator
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Distorted Input/Output Waveform or Spectrum
This topic discusses distorted input signals, including those obtained using an external cable to loop the Daqarta Generator output back to the input. Ideally, the input waveform or spectrum (yellow and red traces) should look like the raw output (green and violet), with only a possible size difference.
There are two general types of problems:
Set the Generator to produce a sine wave for testing, using an external loopback cable. If the input is overdriven, the peaks of the waveform will be flattened. However, you will also see this if the output is overdriven, so the first thing to check is the above Distorted Sound Output topic to make sure that's not the problem.
Then check the Line Levels and/or Master Levels (depending on your card and system). Try reducing these. (The most-sensitive range is 0, with more-negative settings being less sensitive.) If the input waveform changes shape (not just getting smaller), keep reducing (and/or reduce the output volume) until the input looks like the raw output... or at least shows no obvious clipping.
Note that the Spectrum display is much more sensitive at detecting clipping than the waveform display, at least when using a sine wave for testing. It's quite possible to eliminate visible waveform clipping, but still see a forest of low-level harmonics in the spectrum. If so, try reducing the input sensitivity or output volume a bit more to see if the harmonics go away, or at least are greatly reduced. (Some sound cards may exhibit residual distortion that you won't be able to eliminate.)
In this case, the output may not sound bad, but you are not getting the proper output from the Generator.
Sound cards typically offer various options for enhancing music, such as reverberation ("environment") and equalization. Reverberation effects, in particular, can work wonders on the Microsoft GS Wavetable synthesizer that is the default for MIDI output such as Pitch-to-MIDI and DaqMusiq. But such enhancements may seriously compromise measurements or other technical applications that depend on a specific Generator output signal. Unfortunately, different cards may have different options, using custom interfaces that Daqarta can't control, so you have to track them down and disable them manually.
Windows XP: If your sound card has an icon in the Windows system tray, you should start by clicking on that. If not, then go to Windows Control Panel and look for the name of your sound card, such as "Realtek HD Sound Effect Manager", or "USB Multi-Channel Audio Device". (The needed controls will probably not be under the generic Windows "Sounds and Audio Devices".) Click on the icon and Look for a tab marked "Effect" or "Sound Effect", which should open a dialog with "Environment" and "Equalizer" controls. Make sure everything is off.
Vista or Windows 7, 8, or 10:, right-click the speaker icon in the system tray, and click on "Playback Devices". In the dialog that opens, double-click the Speakers icon. (If more than one Speakers icon is present, click on the one with the green check mark.) Under the "Speaker Properties" dialog which opens, click on the "Enhancements" tab and make sure that "Disable all sound effects" is checked. Your device may also have a "Dolby" tab, or something similar. Under that, disable "Sound Space Expander", "Natural Bass", etc. Note that different options may appear when you plug a cable into the output jack (such as a loopback cable to the input jack), so make sure you have the same setup you will actually use with Daqarta. In the Dolby case, disable "Dolby Headphone".
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