Audio encoder, comprising an apparatus implemented in a fixed-point processor for calculating spectral group energies of an audio signal, comprising transformation means for decomposing the audio signal into frames in a time domain and for transforming the audio signal in each frame from the time domain to a spectral domain in order to obtain a group of spectral values for each frame, each comprising an amplitude value in an x-bit representation with the logarithm not taken, such that series of amplitude values result that are divided into different spectral groups; group energy calculation means (24; 80) for calculating spectral group energy for each spectral group in the respective frame as a sum of squares of the amplitude values (22 1 -22 N; 84 1 -84 N), the group energy calculation means (24; 80) comprising: control means (36; 64) for adjusting a respective scaling factor for each spectral group in dependence on the number of the amplitude values of the respective spectral group and the smallest number of unused bit positions in the x-bit representations of the amplitude values of the respective spectral group, scaling means for scaling the x-bit representation with the logarithm not taken (84 1 -84 N) of each amplitude value for each spectral group with the respective scaling factor in order to obtain scaled amplitude values in an x-bit representation; squaring means for squaring the scaled amplitude values in the x-bit representation in order to obtain scaled squared amplitude values in a 2x-bit representation, summation means for summing up the scaled squared amplitude values for each spectral group in order to obtain a respective sum of squares in a representation with the logarithm not taken, means for taking the logarithm (28; 82) for applying a logarithmic function to y bits of the representation with the logarithm not taken of each sum of squares for each spectral group in order to obtain a respective scaled representation with the logarithm taken, wherein y is less than 2x; and rescaling means (32; 76) for adding or subtracting a respective correction value, which results by applying the logarithmic function to the square of the respective scaling factor, to or from respectively the scaled representation with the logarithm taken for each representation with the logarithm taken, in order to obtain a representation with the logarithm taken of each spectral group energy, wherein the spectral group energies of all spectral groups have the same scaling level, an MPEG code stream generator for, based on the spectral group energies of the spectral groups in a representation with the logarithm taken having the same scaling level, generating an encoded MPEG data stream representing an encoded version of the audio signal. control means (36; 64) for adjusting a respective scaling factor for each spectral group in dependence on the number of the amplitude values of the respective spectral group and the smallest number of unused bit positions in the x-bit representations of the amplitude values of the respective spectral group, scaling means for scaling the x-bit representation with the logarithm not taken (84 1 -84 N) of each amplitude value for each spectral group with the respective scaling factor in order to obtain scaled amplitude values in an x-bit representation; squaring means for squaring the scaled amplitude values in the x-bit representation in order to obtain scaled squared amplitude values in a 2x-bit representation, summation means for summing up the scaled squared amplitude values for each spectral group in order to obtain a respective sum of squares in a representation with the logarithm not taken, means for taking the logarithm (28; 82) for applying a logarithmic function to y bits of the representation with the logarithm not taken of each sum of squares for each spectral group in order to obtain a respective scaled representation with the logarithm taken, wherein y is less than 2x; and rescaling means (32; 76) for adding or subtracting a respective correction value, which results by applying the logarithmic function to the square of the respective scaling factor, to or from respectively the scaled representation with the logarithm taken for each representation with the logarithm taken, in order to obtain a representation with the logarithm taken of each spectral group energy, wherein the spectral group energies of all spectral groups have the same scaling level, an MPEG code stream generator for, based on the spectral group energies of the spectral groups in a representation with the logarithm taken having the same scaling level, generating an encoded MPEG data stream representing an encoded version of the audio signal.