[en] Filters for spectrometric amplifiers are considered. Noise and counting rate performances of a common time-dependent filter consisting of a delay line shaper and a contral RC-integrator are analyzed. By the weight function method the general expressions for dispersion of parallel and series noises are derived. The filter normalized noise coefficient is 1.125, the pulse duration is 1.35sub(tau₀)+0.5 mks, where tau₀ is the noise corner time constant of the CR-RC-filter. The experimental dependence of energy resolution on the counting rate is given