Too fast playback when changing soundcard


I’m not sure if this a ardour related problem but I will ask it anyway.

I’m using a line6 podxt too record guitar parts for my project. For playback I want to use my audigy 2 soundcard because the latency on the pod is very high.

However if I record something from the pod within ardour and play it back through my audigy (I do this by stopping JACK and restarting it with the other soundcard) it plays back the guitar parts very fast (like 2 times the normal speed).

Does someone know how to solve this?


Are you using different sample rates on each card? That would definitely cause that kind of behaviour.

Thanks for your reply

In the JACK audio connection kit I’ve set the sample rate for both soundcards to 48000.
Most of the jack settings are similar for both cards. This are the differences:

  • Audigy2:
    Frames/period: 128
    Port maximum: 256
    Timeout (msec): 1000

  • Podxt
    Frames/period: 512
    Port maximum: 256
    Timeout (msec): 2000

I don’t have much knowledge about these things, I found the settings for both cards on the internet.


how do you proceed ? do you disconnect ardour from jack but leave the session opened while you switch sound cards in jack, and then reconnect ardour to jack ? or do you close ardour, stop jack, switch cards in the jack setup, restart jack, restart ardour ?

What does ardour say about your sample rate (top right of the main editor window) when you record and when you play your audio ? It must be what jack tells ardour it is.

By the way, you can also try to play it from another app while ardour is still opened : go to the ardour session directory, then cd into interchange/(session_name)/audiofiles

There you have what you recorded. Play it with e.g. mplayer (jack enabled) or alsaplayer (jack output) or whatever other app that is jack enabled and not ardour. And to be really complete : play it first with your podxt, then the audigy.

Thanks for your reply :slight_smile:

I click ‘disconnect’ in the JACK menu. I then stop the JACK server, change soundcard restart the jack server and then I reconnect from ardour in the JACK menu.

If I play a recorded wav file from the session directory with another player it plays in normal speed. It’s even better…if I create a new project in ardour and import these wav files from the old project (with session -> add existing audio) they play at normal speed in the new project. So i guess that’s a workaround. But it’s not very practical to do this for every guitar part I want to record.

I checked the sample rate in ardour and these indeed differ between the soundcards (but in JACK i’ve set up both cards for 48Khz).
For the audigy 2 it’s 48khz but for the podxtl it is 39.1khz.

I did a check on the podxt and found some very interesting stuff in the manual of the open source driver: (check page 10)

Apperently the pod uses a very uncommon sample rate and it can not be changed :frowning: Off course I can use the work around I mentioned earlier. But what if I want to record while the earlier recorded tracks play. If these were recorded with the audigy they play to slow on the podxt.

So I guess the best solution is to buy a cable and connect the pod to the line-in of my audigy. But any better suggestions are off course welcome :slight_smile:

Sorry for the long post, I was actually discovering all this while typing this post.