I&#39;m very new to Linux audio recording, so I apologize in advance if I&#39;m missing something obvious.<br><br>I have a brand new computer with an M-Audio Delta 44 audio card running the latest version of Ubuntu Studio 8.04. I&#39;ve been experimenting with software synthesizers using a USB MIDI keyboard, and I&#39;ve managed to get QSynth working very well and have had some success recording that. I thought I&#39;d try ZynAddSubFX since it sounds amazing. The problem I&#39;m having is that the sound crackles (that&#39;s the best word I can think of to describe it) when I play it. The very odd thing I&#39;ve discovered though is that if I record ZynAddSubFX in Ardour, I don&#39;t hear any crackling during playback of the recording. It&#39;s only as I&#39;m listening to ZynAdd in real-time as I play it. I&#39;ve tried using different speakers and headphones, but it makes no difference.<br>
<br>I suppose I could just record it and try to ignore the crackling as I play, but it would obviously be ideal to have no crackling at all.<br><br>I&#39;ve tried tweaking both the ZynAdd settings and JACK settings (although my guess is that JACK settings are fine, since I haven&#39;t had any issues with recording live instruments or recording QSynth) but to no avail. I have the sample rate in ZynAdd matching the one in JACK (48000Hz) and have tried different buffer sizes in ZynAdd but haven&#39;t noticed a difference. I&#39;ve also noticed that it usually doesn&#39;t crackle when I&#39;m using the default instrument in ZynAdd, only once I switch to a different one -- then it seems pretty continuous no matter which instrument I switch to after that.<br>
<br>Does anyone have any ideas as to what could be causing this?<br>