An apparatus (90, 190) comprising: a clock source to generate a clock signal in which a noise signal is added to the clock signal as the clock signal is generated and/or routed; an oversampled continuous-time digital-to-analog converter configured to convert an input signal into an output signal having a format that is different from the input signal, the input signal is an input digital signal, the output signal is an analog signal, the oversampled continuous-time digital-to-analog converter comprising: a sigma-delta modulator to perform noise shaping on the input digital signal and provide an intermediate digital signal; a filter (108, 218, 298, 302, 250, 254) arranged to filter the intermediate digital signal and generate a filtered digital signal, the filter (108, 218, 298, 302, 250, 254) having a transfer function having a stop band at a frequency range that includes a frequency of the noise signal or a component of the noise signal; and a continuous-time digital-to-analog converter (110, 216, 296, 300, 248, 252) arranged to convert the filtered digital signal to the analog signal; wherein the clock signal or a signal derived from the clock signal is used by one or more components of the oversampled continuous-time digital-to-analog converter. a clock source to generate a clock signal in which a noise signal is added to the clock signal as the clock signal is generated and/or routed; an oversampled continuous-time digital-to-analog converter configured to convert an input signal into an output signal having a format that is different from the input signal, the input signal is an input digital signal, the output signal is an analog signal, the oversampled continuous-time digital-to-analog converter comprising: a sigma-delta modulator to perform noise shaping on the input digital signal and provide an intermediate digital signal; a filter (108, 218, 298, 302, 250, 254) arranged to filter the intermediate digital signal and generate a filtered digital signal, the filter (108, 218, 298, 302, 250, 254) having a transfer function having a stop band at a frequency range that includes a frequency of the noise signal or a component of the noise signal; and a continuous-time digital-to-analog converter (110, 216, 296, 300, 248, 252) arranged to convert the filtered digital signal to the analog signal; wherein the clock signal or a signal derived from the clock signal is used by one or more components of the oversampled continuous-time digital-to-analog converter. a sigma-delta modulator to perform noise shaping on the input digital signal and provide an intermediate digital signal; a filter (108, 218, 298, 302, 250, 254) arranged to filter the intermediate digital signal and generate a filtered digital signal, the filter (108, 218, 298, 302, 250, 254) having a transfer function having a stop band at a frequency range that includes a frequency of the noise signal or a component of the noise signal; and a continuous-time digital-to-analog converter (110, 216, 296, 300, 248, 252) arranged to convert the filtered digital signal to the analog signal; wherein the clock signal or a signal derived from the clock signal is used by one or more components of the oversampled continuous-time digital-to-analog converter.