I have rolled op amps in this unit in the past. It has been opened up and riser dip switches have been added to the board. I ended up putting the original op amps back in, but kept the risers installed just in case the new owners wanted to change out the op-amps. The unit works and sounds great with the original op-amps. Units works great and I have a 14 day return policy. I have been on eBay for 24 years and 100% positive rating. You can buy in confidence !Shipping is free on this transaction to the lower 48 states. If in Alaska, Hawaii or Canada give me a heads up and I will give you a discounted shipping price.