Kevin,
Yes, putting a buffer before the Quaverato is something that we’ve discovered does often help. This is because of it’s lower input impedance. One option, if you didn’t want to keep a buffer before it, would be to replace R2 and R3 with larger value resistors such as 220K or so. I’m sorry about the trouble this caused you…but i’m glad you figured out how to correct it with the buffer pedal. I have started telling other customers about this, but usually customers who have this issue have low frequency loss instead of high frequency loss, so it didn’t register with me that this could be your issue too. But anyway, i’m glad it’s sorted out.
C16 is actually a .1uF cap (not 1uf), but a 1uF will work just as well for it’s application as a filter to keep the power rails clean.
I hope your Quaverato gives you years of good service. Let me know if you have any more questions/issues.
-Brach