Rumble filter

Although sales of gramophone record may have slumped, there are millions of peopte who still treasu re their record collection. Many record players unfortunately exhibit two undesired side effects: rumble (noise caused by the motor and the tu rntable) and other low-frequency spurious stgnals. The active high-pass Chebyshev filter presented here was designed to suppress those noises. The filter has a 0.1 dB ripple characteristic and a cut-oft point of 18 Hz. A note for designers: a passive filter with the same characteristics was tried: a si xth order Sessel filter; which was soon rejected when it was found that inductors of 600 H were needed!