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X-Y (Vector) Display
(XY Display) The X-Y Vector Display plots the phase relationship between two waveforms. It is useful for identifying the nature of two-channel signals. Readily identified are monophonic vs stereo signals using this function. The instantaneous vector is displayed with a green trace while the averaged angle is displayed in red (provided that the averaging mode is enabled). **The Averaging feature is enabled by using the Averaging Selector and choosing between “None”, “Short”, or “Long”. “None” turns off the averaging display leaving only the instantaneous trace active on the X-Y display. “Short” displays the moving averaged vector displacement angle between the two signals over a 4095 samples interval. “Long” displays the average vector displacement angle over the interval commencing at the time when the play button is started until the time when the stop button is depressed or over the interval of the time highlighted in the play source time display. The averaging interval for the “Long” mode is therefore a variable determined by the user depending on the length of the played file or the highlighted area of the waveform selected to be played and therefore measured. The “Averaging” mode is very useful when trying to measure the phase angle of signals having significant amounts of phase jitter. (Low cost tape recorders often display high levels of phase jitter especially at the upper frequencies in the audio band making the instantaneous graph difficult to use while making azimuth adjustments to the units playback head.) This feature is primarily used to align the azimuth of analog tape deck recording and playback heads. To do so, a known pre-recorded azimuth alignment tape is required containing a fixed frequency tone. The X-Y Vector display in conjunction with your azimuth tape and the Time Offset feature can be used to fine-tune a recorders time alignment without the necessity of having to take a screwdriver to your tape deck's head alignment adjustment screws*. The goal here is to correct the azimuth of the .wav file using the File Conversions Filter with the Time Offset slider control. Preview the .wav file with the X-Y Vector Display showing, and adjust the Time Offset slider control until a 45 degree positive sloped (up and to the right) straight line is seen on the display. That will be the optimum value of azimuth correction.
An important “cousin” view of the X-Y display is the “View Channel Phase vs Time” function found under the Forensics Menu (found in the Forensics version of the software only). This routine plots the average phase angle between the two channels vs time which can be useful in Forensics authentication applications. Please refer to the Forensics Menu section of this users guide for more details regarding this feature.
*Note: The optimum method for adjusting analog tape head azimuth is via the X-Y display in conjunction with an analog azimuth reference tape and by directly adjusting the playback head azimuth screw on the tape player.
The X-Y Vector Display Showing Proper Azimuth Alignment
The following features will be found on the X-Y Vector display:
Here is a listing of some common vector displacements, which can be observed on the X-Y Vector Display. They have the following meaning and are sometimes referred to as Lissajous figures :
The X-Y Vector Display Showing a Stereophonic Signal
The X-Y Vector Display Showing 90 degree phase shifted signals (green)
(45 degree average phase shift as shown in red)
*Note 1: In these examples, the Right channel would be twice the frequency of the Left input. If the figure 8 were lying on its side, then the Left channel would be twice the frequency of the Right input.
**Note 2: The Vector Angle Averaging feature is only available on the DC Forensics10 version of the software.
(XY Display) The X-Y Vector Display plots the phase relationship between two waveforms. It is useful for identifying the nature of two-channel signals. Readily identified are monophonic vs stereo signals using this function. The instantaneous vector is displayed with a green trace while the averaged angle is displayed in red (provided that the averaging mode is enabled). **The Averaging feature is enabled by using the Averaging Selector and choosing between “None”, “Short”, or “Long”. “None” turns off the averaging display leaving only the instantaneous trace active on the X-Y display. “Short” displays the moving averaged vector displacement angle between the two signals over a 4095 samples interval. “Long” displays the average vector displacement angle over the interval commencing at the time when the play button is started until the time when the stop button is depressed or over the interval of the time highlighted in the play source time display. The averaging interval for the “Long” mode is therefore a variable determined by the user depending on the length of the played file or the highlighted area of the waveform selected to be played and therefore measured. The “Averaging” mode is very useful when trying to measure the phase angle of signals having significant amounts of phase jitter. (Low cost tape recorders often display high levels of phase jitter especially at the upper frequencies in the audio band making the instantaneous graph difficult to use while making azimuth adjustments to the units playback head.) This feature is primarily used to align the azimuth of analog tape deck recording and playback heads. To do so, a known pre-recorded azimuth alignment tape is required containing a fixed frequency tone. The X-Y Vector display in conjunction with your azimuth tape and the Time Offset feature can be used to fine-tune a recorders time alignment without the necessity of having to take a screwdriver to your tape deck's head alignment adjustment screws*. The goal here is to correct the azimuth of the .wav file using the File Conversions Filter with the Time Offset slider control. Preview the .wav file with the X-Y Vector Display showing, and adjust the Time Offset slider control until a 45 degree positive sloped (up and to the right) straight line is seen on the display. That will be the optimum value of azimuth correction.
An important “cousin” view of the X-Y display is the “View Channel Phase vs Time” function found under the Forensics Menu (found in the Forensics version of the software only). This routine plots the average phase angle between the two channels vs time which can be useful in Forensics authentication applications. Please refer to the Forensics Menu section of this users guide for more details regarding this feature.
*Note: The optimum method for adjusting analog tape head azimuth is via the X-Y display in conjunction with an analog azimuth reference tape and by directly adjusting the playback head azimuth screw on the tape player.
The X-Y Vector Display Showing Proper Azimuth Alignment
The following features will be found on the X-Y Vector display:
- X-Axis displacement (Horizontal), which corresponds to the Right Channel Input
- Y-Axis displacement (Vertical), which corresponds to the Left Channel Input
- X-Axis gain control slider (Horizontal & bottom in position)
- Y-Axis gain control slider (Vertical & left in position)
- Averaging Selector**
- None: Averaging function Turned Off
- Short: Averaging Interval = 4095 Samples
- Long: Averaging Interval is Variable depending on length of “played” file
- Average Angle Display Window**: Displays the Average Phase Angle value with up to 6 digits of resolution.
Here is a listing of some common vector displacements, which can be observed on the X-Y Vector Display. They have the following meaning and are sometimes referred to as Lissajous figures :
- Straight line at 45 degrees with a positive (up and to the right) slope = Signals are in phase and are Monophonic.
- Straight line at 45 degrees with a negative (down and to the left) slope = Signals are out of phase and are Monophonic. An example of a situation that could cause this would be a miss-wired Stereo Phono cartridge or a miss-wired balanced input to the soundcard.
- Straight horizontal line only = Monophonic, Right channel only signal.
- Straight vertical line only = Monophonic, Left channel only.
- Straight line at 45 degrees with a negative (down and to the left) slope = Signals are 180 degrees out-of- phase.
- Circle = Signals are 90 degrees phase shifted.
- Elliptical tilted up and to the right = Signals are between 0 to 90 degrees phase shifted.
- Elliptical tilted up and to the left = Signals are between 90 and 180 degrees phase shifted.
- Frozen vertical figure "8" = Signals are frequency phased locked to one another but 2:1 in frequency ratio.*
- Moving vertical figure "8" = Signals are not frequency locked, but are about 2:1 in frequency ratio.*
- Random pattern of squiggly lines on the screen and average (red) signal up and to the right = Stereophonic audio signal in proper phase.
- Random pattern of squiggly lines on the screen and average (red) signal up and to the left = Stereophonic audio signal with improper phase.
The X-Y Vector Display Showing a Stereophonic Signal
The X-Y Vector Display Showing 90 degree phase shifted signals (green)
(45 degree average phase shift as shown in red)
*Note 1: In these examples, the Right channel would be twice the frequency of the Left input. If the figure 8 were lying on its side, then the Left channel would be twice the frequency of the Right input.
**Note 2: The Vector Angle Averaging feature is only available on the DC Forensics10 version of the software.