Tanks for the tips. Racamuti, the amps I want to use are different. Both are restored Bedini amps. The 25/25 DE has better mids and high range, the 100/100 DE has better bass control. Arian, this is being used for speaker design development. I’m making the crossovers too so no issues that need a custom designed active crossover. This is being used to get the best performance from the two amps I’m using for development. But the Marchand custom unit might be the next step once I’m comfortable with this path. I already have access to a dsp processor. Maybe it’s not a good one because I don’t like what it does to the midrange at any setting. Or possibly because I primarily use analog sources. That means starting with analog, digitizing, manipulating, then conversion back to analog before amplification. A better Dsp may also be on the list as next steps. I will be hunting for something used I can work with. The pass sounds worth searching for.