| abstract |
(57) Abstract: In a magnetic recording / reproducing apparatus, optimization of an equalizing circuit, optimization of various conditions at the time of recording and reproduction, and the like are performed in a short time. And a signal processing circuit for realizing the same. A variable gain amplifying circuit (VGA), a gain control circuit (GCC), and a DAC for a current output type AGC connected to an output of an equalization circuit for sequentially detecting the amplitude of an output signal of the equalization circuit. (VDAC) 30, an identification circuit 44 that receives an output signal of the equalization circuit 20 as an input signal and identifies an output signal, and an identification circuit 44 that identifies the input signal and the output signal of the identification circuit 44. An error calculation circuit 41 for calculating an error relating to the amplitude of the signal, A determination circuit 56 that sets a threshold value and outputs a count signal with an error signal equal to or greater than the threshold value, and a counter 49 that counts the count signal. |