Pretty sure you'd want to attenuate the output, not the input. You want the amp to have as much to work with as possible, without overloading. Since overloading the B22 input is pretty unlikely, you'd want to do the attenuation later.
This one is mine. What's not immediately obvious is the lot is all hill, and steep enough that there are times I feel like I'm going to die mowing it every single time.