Time/sampling problem recording from DAT at 48k

Audacity 2.0.3 on Win 8.1. Input device is a Soundblaster X-Fi HD USB, latest drivers for Win 8.1. The tapes are 48k and when I record them the time is off. The Creative panel shows that input is 48k, Audacity is set to 48k. Yet as the tape records, the window shows 19:10 when the playback is actually 17:36. A 35 minute section records as 38 minutes. Playback does sound a bit slow although that isn’t easy to tell. It appears to be the difference between 48k and 44k but I didn’t work out the math.

Is there some setting in Audacity that I’ve missed or any other suggestions to figure out what is going on?

If it a 44100/48000 Hz issue, you can correct the problem after recording using Effect > Change Speed with Percent Change of 8.844.

It is probably a sample rate mismatch somewhere in Windows. Try the following if you have not already done so which should let Audacity request the sample rate direct from the sound card without resampling.

  1. Right-click over the speaker icon by the system clock, then choose “Recording Devices”. Right-click over the X-Fi then choose “Properties”. Click the “Advanced” tab, then put a checkmark (tick) in both Exclusive Mode boxes.
  2. Choose the main “Playback” tab then right-click over your chosen playback device, choose “Properties,” click the “Advanced” tab and similarly enable both Exclusive Mode boxes.
  3. Restart Audacity or use Transport > Rescan Audio Devices then choose “Windows DirectSound” host in Device Toolbar . Choose the correct playback and recording device.
  4. Ensure Audacity Project Rate is 48000 Hz.

Are you using optical out from the DAT player and optical in on SoundBlaster? You won’t get unchanged audio without that.


Yes, optical out from a Panasonic SV3800 into the SB. On the Advanced tab in the Playback properties both boxes were already checked, but the dropdown for the Default (shared?) sampling rate was 44. I changed that to 48 and the next tape came in perfectly. I’ll re-record the other two that I had already done rather than change the speed. Thanks for the assist.

I’m having trouble with some tapes that I recorded off the radio at 32k, but I can’t even get the SV3800 to play back a 32k tape. It shudders a bit and then has to be turned off and back on. I have a Sony D7 that can probably handle that but I don’t think I even want to guess how to get Windows to pass that through.

Yes the “Default Format” sample rate and bit depth only apply in Shared Mode, and not in Exclusive Mode. However I assume you had the Audacity host set to “MME”? Under MME, Shared Mode will still apply, and Windows would have resampled from 48000 Hz to 44100 Hz, which is probably where the audio got slowed down. Then Audacity would resample back to the project rate (48000 Hz in your case).

“Windows DirectSound” should be the better choice. Under MME, Windows will (as I understand it) always resample to 44100 Hz, even if Default Format is some other rate. However, setting Default Format to the input rate probably prevents the Windows resampling causing a speed change.

The number of channels set in Default Format always applies, even in Exclusive Mode.