(Sorry for the delay… So, I’m not sure I understand your question, so forgive me if I’m way off in my answer!)
1st of all, I treat the BeatBuddy like a separate instrument…not a pedal in my pedalboard chain, so it’s not connected at all to my guitar, and the BeatBuddy is not routed into or out of my looper. The BB gets it’s own channel on my mixer, or if I’m just using my amp at home, I plug the BB in through the Aux channel on the back of my amp. The Aux channel has it’s own volume control. That might be the whole answer to your question.
If you were asking about the HOW I get my BB and RC-300 on the same tempo, keep in mind I had absolutely no experience with midi when I first tried connecting just the RC-300 and BB with the midi cable, and if I remember correctly, it was a disaster. (I’ve since purchased Onsong and a Midi Solutions Quadra Thru midi splitter, and had much help in multiple forums to get my songs programed with the patches for the BB, my VoiceLive 3 Extreme, and my RC-300 AND IT WORKS AMAZINGLY!). But before the midi connections, I did however have a a bit of success with pre-programming the RC-300 to match the BB tempo as I mentioned above. This DID require some work in the BB first!
I used the BB Manager program on my computer to export and then import (BBM version of copy and paste) each song that I wanted to customize–mainly to save it in my own folder on the BB and re-title the beat from Blues 2 to Gimme One Reason and change tempo from default 120 to actual 102 (for example–I can’t remember the exact tempo).
BB is all setup, so we’re back at the looper. I’m sure there are better ways to do this, but in order to get the RC-300 at the same tempo as the BB, I would create a short 1 or 2 bar loop with simple quarter note strums while the selected BB song is playing in the background (my looper mic is off or the mic input is turned all the way down, so it’s not picking up the BB sounds).
Once recorded, I would open the track edit button to check what tempo the looper thinks I recorded the loop at (hopefully close to the BB tempo, but if I use a different strum pattern, sometimes it shows up completely different!!!–the RC-300 is a wild animal sometimes, but I love it). If the tempo is close (ie: BB says 102, looper says 102.3), I just adjust the looper time down to 102.0). I’ll play through the loop a bit to make sure it sounds good and works with the BB without any “drift”. If you want to save that loop and tempo on the RC-300 you hit {write} {write}. If you only want the tempo saved but want a clean open loop to do live looping next time, I believe you have to bounce this to a new blank preset, then delete the loop from the track, re-save it and the tempo should still be there. I’m not sure why, but if you do this on your original loop, the track will be empty with your custom tempo lost.
If you want to save your loop for whatever reason (some loop building gets a little long for an audience to sit through), you can just play your loop, check the tempo, tweak it to match the BB if it’s close, and save it. Now all you have to do is start your BB and start looping on the beat (that’s the tricky part!). (It has been a while since I’ve done this, but I think your RC-300 preset might need to be set up to use the given tempo.)
This set up lets me (or my sound guy) adjust the BB and loop level separately so it doesn’t overpower the loop (or can be heard with the loop). We eventually took this further and separated the guitar sound to it’s own channel on the mixer and then routed it back into the looper through a Morley ABC switch (I also have a dedicated bass pedal routed into this, and now my vocals from my Voicelive 3, AND a keyboard-sharing the switch with my guitar since I would never play those two together), so the sound guy can control the guitar and loop levels separately as well. I love the higher quality sound of my live loops recorded this way, so I’ve had to learn how to use the “scary” mixer for myself when the sound guy can’t make it to a show.
Anyway, I believe I’m now off topic–sorry! I hope I got close to answering your question and wasn’t telling you what you already knew. (insert sheepish grin and shrug here). If not, keep asking…I will dig out my notes and look up the YouTube videos, forum answers, etc. that helped me.