we designed a USB Audio Class 2 interface for recordings on PC (there is no playback function provided in this interface.) This works correctly with several other recording programs (Cubase, TwistedWave, WavePad) but with Audacity we encounter severe problems on two completely different MACs. BTW, except ours, I don’t have any other USB Audio Class 2 signal source.
Up to 96 kHz everything is ok. From 176.4 kHz on, the first signs of the problem appear. At 192 kHz a signal is heavily disturbed as can be seen on this screen shot:
The signal is recorded correctly for a couple of ms, then a gap follows where either the signal is replaced by zeros or zeros are inserted, afterwards the recording continues and so on. The upper recorded track shows a 10 Hz (left) and a 100 Hz (right) sine wave and the lower track a 10 Hz (left) and a 10 Hz (right) sine wave. (The “hick up” at approx. 10 ms is not too interesting here, but it does not appear with other recording programs either. I can’t even exclude that it is created by our interface and just “cut off” by the other programs.) The position of the gaps is always identical, i.e., it is not a coincidence that the gaps in these tracks are aligned underneath each other.
To the best of my belief, for several reasons this can only be explained by a bug in Audacity:
- All other programs I was able to test did not show any error, even when one signal is recorded synchronously by Audacity and another recording software.
- When I switch to a project rate of e.g. 48 kHz the recording is perfect, too. (I assume that Audacity does the down sampling.)
- The behavior is identical on two different PCs. Only the sizes of the gaps vary slightly and become sometimes irregular.
I use the newest Audacity 2.1.0. It was installed by the .dmg. One of the PCs I have for tests is a MacBook with OS X 10.7.5 (Lion) and the other is a Lenovo Think Pad with Mavericks (10.9?).
I would be grateful for any help and should we be able to help to correct the (assumed) error, please let us know, we would be glad. Particularly because I was forced to try out several other programs and had to experience why I definitely would want to stay with Audacity.