A method for producing a polycondensate melt from a primary material and a secondary material from materials of substantially the same type and of the same basic chemical composition, comprising following steps: - providing a first partial melt stream (I) of the primary material, which primary material has been synthesized from at least one monomer, - determining a first measured value of the intrinsic viscosity of the first partial melt stream (I) of the primary material, - providing a second partial melt stream (II) of the secondary material, which secondary material is formed of a polycondensate material that has already been processed at least once, - determining a second measured value of the intrinsic viscosity of the second partial melt stream (II) of the secondary material, - forming a difference value from the first measured value of the intrinsic viscosity of the primary material and the second measured value of the intrinsic viscosity of the secondary material, - increasing or reducing the intrinsic viscosity of the second partial melt stream (II) of the secondary material to the determined first measured value of the intrinsic viscosity of the first partial melt stream (I) of the primary material by means of a first melt treatment device , based on of the determined difference value, or unchangedly maintaining the intrinsic viscosity of the second partial melt stream (II) of the secondary material based on the determined difference value, - subsequent formation of a common melt stream of the polycondensate melt from the second partial melt stream (II) of the secondary material, in which the quality defined by the intrinsic viscosity has been aligned with or already has the quality of the first partial melt stream (I), by means of combining and uniting with the first partial melt stream (I) of the primary material. - providing a first partial melt stream (I) of the primary material, which primary material has been synthesized from at least one monomer, - determining a first measured value of the intrinsic viscosity of the first partial melt stream (I) of the primary material, - providing a second partial melt stream (II) of the secondary material, which secondary material is formed of a polycondensate material that has already been processed at least once, - determining a second measured value of the intrinsic viscosity of the second partial melt stream (II) of the secondary material, - forming a difference value from the first measured value of the intrinsic viscosity of the primary material and the second measured value of the intrinsic viscosity of the secondary material, - increasing or reducing the intrinsic viscosity of the second partial melt stream (II) of the secondary material to the determined first measured value of the intrinsic viscosity of the first partial melt stream (I) of the primary material by means of a first melt treatment device , based on of the determined difference value, or unchangedly maintaining the intrinsic viscosity of the second partial melt stream (II) of the secondary material based on the determined difference value, - subsequent formation of a common melt stream of the polycondensate melt from the second partial melt stream (II) of the secondary material, in which the quality defined by the intrinsic viscosity has been aligned with or already has the quality of the first partial melt stream (I), by means of combining and uniting with the first partial melt stream (I) of the primary material. <EOS>