I see on the Broughton website that the LP/HP has a 1M input impedance and suggests that it is high enough to accommodate acoustic pickups, but would it be beneficial to buffer the piezos in my stick bass (there are 2) before running them to the frequency interchange? I am planning to replace the existing pre/headphone amp circuitry. Any concerns running 2 piezos (buffered or not) in parallel into the FI?