I decided to post this as a new thread because I didn't want it buried at the end of the old one: (http://www.talkbass.com/forum/showthread.php?t=210002) A quick recap: I use a RS Solo pickup and noticed wild speaker-cone excursions with my new iAmp200. This resulted from the amp's response to infrasonic frequenncies. Mike Dimin put me in touch with Gary Gibilisco, the amp's designer. The bottom line: I couldn't be happier! First of all, Gary was enormously appreciative of my detailed analysis of the problem, exhibited a great sense of trust, and an absolute devotion to solving the problem. He was very candid in telling me that EA had heard mention of the problem but had never before had a customer with sufficient expertise to provide them with detailed feedback. The iAmp200 does have a "roll-off" (high-pass) circuit to attenuate extremely low frequencies. In the case of a double bass with a piezo pickup, it just was not severe enough. Gary immediately issued a call-tag for my iAmp200 and it was shipped back at EA's expense. Within about ONE DAY, Gary sent me a loaner amp which he had modified such that the roll-off began at a slightly higher frequency and using a capacitor with smaller tolerance around its nominal value. It worked! The wild cone excursions were tamed and the desired low-end response (40 Hz and above) was not reduced to any substantial extent. Given the success, Gary modified my amp in the same way and I received it yesterday. I'm all set. Gary also encouraged me to keep his loaner for a few days so that I could fully compare the two. Well, it only took a short time last night to discover that I could hear no difference. Kudos to the guys at EA. They stood FIRMLY behind their product and went beyond the call as far as I'm concerned. Customer service just doesn't get better than what I experienced. We in the bass community are, indeed, fortunate to have companies like EA serving us. Techy note: How does a double-bass with a piezo element produce extremely low frequencies given that the fundamental of the vibrating E-string is around 40 Hz? When you tap a string (as when a finger lands on the string during normal playing), you create an impulse that contains a broad range of frequencies. Normally, the very low frequencies contained in the impulse are never transmitted-- certainly not acoustically through the bass. The piezo element, on the other hand, is a broadband device and it will pass these frequencies. One does not expect them to be passed by the amplifier and speaker either. In my case, the iAmp200 and Wizzy cabinet were quite willing to pass them! Providing the iAmp with a bit more roll-off below 30 Hz cured the problem.