10th January 2019 at 10:07 #44157
I recently bought a uTrack24 to evaluate as a recorder for a 24-channel hydrophone array we are using for underwater noise measurements. Not, I admit, the standard application, but on paper the uTrack24 seems ideally suited to the purpose. I’ve been doing a bunch of tests on it and all except one indicate it will work extremely well. The one issue is that the signals recorded on channels 7, 8, 15, 16, 23 and 24 appear to be delayed with respect to the other channels by 119 microseconds (at 48 kS/s) or 129 microseconds (at 44.1 kS/s), both of which correspond to a delay of 5.7 samples. All other channels align precisely, and the six ‘slewed’ channels align precisely with one another. (The tests were done using the Utrack 24’s internal clock.) We will be doing beamforming with the array which requires precise timing between the channels so I’m wondering why this channel slew is occurring. If we can rely on it always being the same then we can compensate for it in our post-processing software. The worst case scenario would be if it isn’t consistent between recordings. Any light you can shed on this would therefore be appreciated. Alec10th January 2019 at 11:25 #44161
Thank you for your detailed feedback.
Yes I can confirm that delay on the last two channels on the 8 channels groups, it happens due to the A/D converters. (CH 7-8; 15-16; 23-24)
If your application is sample accuracy, there’s two solutions for you.
1. As you can count on constant delay on those channels, you can compensate that with post processing.
2. Use digital input instead of analog. There are 3 option cards available for the device: ADAT
AudioLan (AES67)10th January 2019 at 11:53 #44165
Many thanks for your prompt response. Unfortunately the signals are analog out of the hydrophone preamps, so the whole point of the uTrack24 is to do the A/D conversion and Option 2 isn’t a possibility. However as the delay is constant we should be fine.
I am, however curious: are you using 8-channel A/D converter chips that have this particular characteristic or multiple smaller channel count chips?
Alec10th January 2019 at 15:53 #44178
To able to get this price range and still decent quality in uTrack24 has 6in/8out converters and in the recording path we had to use an 2 channel AD on the last channels.11th January 2019 at 01:11 #44192
I see, that explains it. I’m very impressed with the uTrack24 overall and now that I know about the different channel delays it will be fine for our application as we can easily compensate. Many thanks for your assistance.
Alec11th January 2019 at 09:01 #44197
You are welcome!
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