How do I do a channel ID test on an APx585? Using the Test Channel button in Signal Path Setup seems to be a manual operation only. That is, I have to click the channels one at a time and observe the result. I’m looking for an automatable test—one that I can put in a sequence and get a pass/fail result on.
If you are testing a device like an AV receiver with a Dolby or dts decoder in it, the Audio Precision Blu-ray disc (APx-BD1) contains encoded waveform files that were constructed specifically for this purpose. These encoded files can be downloaded from our web site.
If your signal path does not include a device that does Dolby or dts decoding, the process is less direct. Linear PCM files are 2-channel (stereo). You can create four stereo .wav files, each containing a pair of different tones, and then map them to appropriate channels. When using the linear mode the system can only test two channels at a time, but you can still automate this by having four instances of the frequency measurement in your sequence.
For example, see the APx project file named APx585 Channel ID.approj. This project contains one signal path with 4 instances of the frequency measurement named Ch 1 & 2, Ch 3 & 4, etc. For each measurement, a .wav file has been created with unique tones that help to identify the channel. Each waveform has tones at two distinct frequencies, labeled Tone 1 and Tone 2, as listed in Table 1. Tone 1 is the main tone, with a level 20 dB higher than Tone 2. Tone 2 is at a much lower frequency than Tone 1, and it is included in case the channel being tested in the DUT contains a low pass filter (e.g., a subwoofer or LFE channel in an AV receiver). This way, if the low pass filter eliminates the main tone, the second tone is still available for identification purposes. This same scheme is used for the Channel ID files on the AP Blu-ray disc noted above.
|
.wav file |
Left Channel |
Right Channel |
||
|
Tone 1 |
Tone 2 |
Tone 1 |
Tone 2 |
|
|
Channel_ID_1-2_48_24.wav |
51 Hz |
1 kHz |
52 Hz |
2 kHz |
|
Channel_ID_3-4_48_24.wav |
53 Hz |
3 kHz |
54 Hz |
4 kHz |
|
Channel_ID_5-6_48_24.wav |
55 Hz |
5 kHz |
56 Hz |
6 kHz |
|
Channel_ID_7-8_48_24.wav |
57 Hz |
7 kHz |
58 Hz |
8 kHz |
In the project file (APx585 Channel ID.approj), in each of the four frequency measurements in Signal Path 1, the appropriate generator channels have been enabled and measurement limits equivalent to the Tone 1 frequency ± 5 Hz have been set. Hence, if you run the sequence, the report will indicate a Pass result if the channel outputs are connected to the correct inputs. In the project file, the signal path has been set to Analog Balanced Output and Analog Balanced Input, so that the 8-channel loopback cable can be used for convenience. This is just for illustration purposes, and you should change this to suit the DUT.
This approach can be used with any instrument in the APx family, and customized appropriately. The individual waveform files are also included for the convenience of users who want to make their own project file.
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Ref:SLX3969 / Joe Begin
Channel ID Test on APx585 Sample project for KB Article 103
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