My colleagues and I are building a phase adjuster for LFN (Low Frequency Noise) audio signals. Since we would like to be able to adjust a range of signals that encompasses a range of around 50-400 Hz, an op amp-driven, analog solution would not be economical, nor efficient. Since we need to be able to adjust a range of frequencies, we are looking at a digitally converted solution utilizing potentiometers. If a digital device is not feasible, can anyone describe how to construct an analog solution for real-time phase adjustment? Has anyone had any experience in this area? Does anyone know of any resources one can use to construct the aforementioned device? Thanks in advance.