Hi, ive tried the process of elimination, and the pop and crackle is definately only happening playing bass through my boss digital 16track, out digital out/SPDIF and into digital in/SPDIF on my presonus audiobox 1818 sound card......im running through the boss 16 track cause i like the ef and the sound of the preamps.......and as i said ive tested everything else out, no its not the cables, no i dont have an issue if i plug directly into the presonus sound card, and no i have no crackle and pop if i listen to the bass on the actual boss 16 track

When you use SPDIF one device needs to be the clock source. Try switching to which ever your not using at this point. 

Sorry i dont quite understand, im using both the 16track and the sound card, im running through the 16 track into the sound card,so and am i assuming you mean one to clock and whats the other one set to?.....ive never used clock setting

actually thanx, righteo, i found the spdif option in audiobox section, switched it from internal clock, to spdif clock, and yes that worked, thanx

Hey,so recorded using spdif clock, my click track was recorded onto my audio bass track?can i eliminate this problem?

Your problem is not related to your projects tempo. It's to do with the sample rate clocks which make sure that samples line up between the 2 machines. If one can't be set to master and the other to slave then you will get sample rate mismatches. The sound you hear is a symptom of that.

You either need to fix the synchronising problem or just use one device.

Right...sorry imstill not on top of it........my sound card is set to spdif clock

Are you monitoring the click track on the mixer? Sounds like you looped the click track back into Sonar via your monitoring system. I don't think Mike understood your problem. 

ha ha,yeah,how fast can i sort this problem out.......im just plugged into my presonus 1818 audiobox interface this time,  input 1 is turned up and headphones also
 

and im selling the ufx1604 because it haas ****house preamps.....probably going to go backto the presonus studiolive