Encoder for encoding an input audio signal comprising signal frames into quantized bits (108, 208), the encoder comprising: - at least one matrix generation module configured to generate, for each frame of the input audio signal, a signal matrix (103, 203, CovM#1,..., CovM#N) comprising matrix coefficients obtained from that frame, wherein the signal matrix comprises amplitudes of a frame of the audio signal or is computed based on the amplitudes of the frame of the audio signal; - at least one quantizer module comprising: - a partition module (105, 205, M2V#1,..., M2V#N) configured to group the matrix coefficients of each signal matrix into a plurality of partition vectors (106, 206, v 1 1,..., v L 1), and - a vector quantization module (107, 207) comprising a plurality of vector quantization schemes ( VQ 1 1,..., VQ L 1) and configured to, for each partition vector (106, 206, v 1 1,..., v L 1), select one of the vector quantization schemes ( VQ 1 1,..., VQ L 1) and quantize that partition vector according to the selected vector quantization scheme to obtain the quantized bits (108, 208), wherein, in an adaptive mode, the partition module is able to group differently the matrix coefficients obtained from different frames, and/or the vector quantization module is able to select different vector quantization schemes for partition vectors obtained from different frames. - at least one matrix generation module configured to generate, for each frame of the input audio signal, a signal matrix (103, 203, CovM#1,..., CovM#N) comprising matrix coefficients obtained from that frame, wherein the signal matrix comprises amplitudes of a frame of the audio signal or is computed based on the amplitudes of the frame of the audio signal; - at least one quantizer module comprising: - a partition module (105, 205, M2V#1,..., M2V#N) configured to group the matrix coefficients of each signal matrix into a plurality of partition vectors (106, 206, v 1 1,..., v L 1), and - a vector quantization module (107, 207) comprising a plurality of vector quantization schemes ( VQ 1 1,..., VQ L 1) and configured to, for each partition vector (106, 206, v 1 1,..., v L 1), select one of the vector quantization schemes ( VQ 1 1,..., VQ L 1) and quantize that partition vector according to the selected vector quantization scheme to obtain the quantized bits (108, 208), wherein, in an adaptive mode, the partition module is able to group differently the matrix coefficients obtained from different frames, and/or the vector quantization module is able to select different vector quantization schemes for partition vectors obtained from different frames. - a partition module (105, 205, M2V#1,..., M2V#N) configured to group the matrix coefficients of each signal matrix into a plurality of partition vectors (106, 206, v 1 1,..., v L 1), and - a vector quantization module (107, 207) comprising a plurality of vector quantization schemes ( VQ 1 1,..., VQ L 1) and configured to, for each partition vector (106, 206, v 1 1,..., v L 1), select one of the vector quantization schemes ( VQ 1 1,..., VQ L 1) and quantize that partition vector according to the selected vector quantization scheme to obtain the quantized bits (108, 208),