[LAU] Popping sound at the start of every note on Bristol synths.

Hello. I've been trying Bristol as a replacement to another jack synth that I use. Mainly because it doesn't have MIDI control messages support and Bristol does. However, I've found that there is a popping sound at the start of every note. This is more apparent in some models/presets than others. I'm pretty sure my jack configuration is fine (has been working fine with other synths, ardour, puredata, qtractor, etc.) and I've also tried ALSA and two different sound cards (laptop internal and firewire). I also tried outputting Bristol straight to system output, passing through Ardour, different frame rates and buffer sizes (big ones) and it's always the same... Here is a recording of what it sounds like: http://public.elsoftwarehamuerto.org/Bristol.flacIs this a known issue with Bristol? can someone advice how to get rid of it? Cheers! RV