It's been a few years since I've turned this amp on having moved on to better amps. This is what I preferred at the time...
Edited by Tribbs - Today at 8:15 am
It might be possible to get op amps directly from the manufacturer as free samples. For example, check out the link below for instructions on getting free samples from TI
My favorite op amp for the LD1+ is the MUSES02. Unfortunately it is more expensive than most. I have found the eBay vendor janeh2100 to be reliable with competitive prices.