Interesting note on the Barton website concerning this module:
"1.It's out of tune!Check your +5V supply. If you're running on less than 5V your quantizer's notes will seem flat, if it's higher they will seem sharp. If you're using an adjustable +5V supply, then adjust it until you're in tune. If you're using a 7805 on board regulator, swap it out for a different one. I buy the cheapest 7805s I can find and I've never gotten one so out of spec that it bothered my ears, you're probably going to get a good one. You can also use the 7805 to LM317 adaptor PCB to make a tiny adjustable +5V supply."