One of those simple little products for which many of us wish is finally available. A little over a year ago, our own fdeck and I had a dialogue about the design of a useful pre-amp/adjustable high-pass filter (pre/HPF). I bench-tested a pre-production version and after a tweak here and there by fdeck, I must say that this is one sweet little circuit from the standpoint of both laboratory measurements and months of use with my DB and rig (RS-2 pickup, EA iamp200, Wizzy 12). The pre/HPF incorporates a 10M-ohm input and a 12-dB/oct high-pass filter with the corner frequency adjustable (via a knob on the outside) from about 40 Hz to 110 Hz. Only discrete components (transistors) are employed. There are no op-amps in the circuit. The latest production versions also include a phase-reversal switch. All of this is encased in a palm-sized box and the circuit is powered by a 9-volt battery that is connected only when a plug is inserted into the output jack. The battery should provide well over 100 hours of use. My own measurements showed the frequency response of the pre/HPF to be essentially ruler-flat above the high-pass cutoff at least out to any frequency that could imaginably be relevant to a DB player. That is, the device is not "voiced" in any way. Distortion and noise are acceptably low even when the pre/HPF output is over 1 volt. I'll leave the geek-talk there. Measurements aside, from my months of actual use of the pre/HPF, I can say that it sounds great. More to the point, it has no "sound." It just does its job. I have never once had an issue with clipping, distortion, or noise of any kind. It effectively solves the "infrasonics problem" about which I so often speak here. I would not want to be without it. If you're interested, I suggest you send fdeck a PM. In the spirit of full disclosure, I want to explicitly state that I have no financial interest in this device at all. In return for my assistance in testing and measurement, fdeck let me keep the prototype he sent to me. P.S.-- My understanding is that the price is $50 plus shipping.