As with all amplifiers that use a switching output stage, examining the Halcro Logic MC20's performance on the test bench was complicated by the presence of RF energy in its output. Unless this energy is filtered, you can never be sure that you're not actually measuring the interaction between the RF content and the test gear instead of the absolute performance of the amplifier under test. (For a discussion of this subject, see my "Measurements" sidebar accompanying Robert Deutsch's review of the PS Audio GCC-100 amplifier in January.)
Fig.1, for example,…