Although I've said that the Corona C15 has a class-D output stage, MBL's chief engineer, Jürgen Reis, refers to the design as a "Linear Analog Switching Amplifier Design" (LASA). As he explained in an e-mail, "the only thing our LASA concept has in common with typical class-D is the low heat radiation. Nothing else. LASA stands for the complete concept, not only for the switching core module." The C15 uses a version of the well-respected Hypex class-D module, designed by Bruno Putzeys, but Jeremy Bryan, clarified via e-mail that "the boards that contain the UCD modules are made for MBL to our proprietary specification. They are not standard boards available to any consumer or other OEM customer." Reis confirmed that MBL's OEM modules "differ from the regular one in parts, measurements and sound . . . This work with Hypex modules started about 7 years ago. Those [first modules] were good, but it needed time [for me] to understand what parameters influence the sound . . . and to change the good basic concept [to the point where it matches] our 'house sound.' . . . [W]e changed the modulator behavior in order to get our requested THD performance and changed the input parts to get the tonal balance required."