| 摘要 |
PURPOSE:To reduce the contents of an ROM and at the same time eliminate the unnaturalness during a switching mode, by carrying out a logarithmic interpolation from the coefficient before switching to the coefficient after switching when the characteristics is switched for a filter is used to an electronic musical intrument or the like. CONSTITUTION:The characteristics of a digital filter is switched by selecting the eoefficient e.g. KB which is stored in an ROM and by renewing the coefficient KA applied to a multiplier via an interpolating circuit 15. The clock phi1 is supplied to the circuit 15. The KA is held in a register 18 when the characteristics is switched, and the KB is supplied to a register 16 in the form of KI. The output KB-KA= DELTAK of a substractor 17 is turned into DELTAK/2 through a shifting circuit 19 and then latched to the register 18 in the form of KA+(DELTAK/2) through an adder 20 and in the timing of the next clock phi1. The outputs DELTAK/4, DELTAK/8- are delivered through the circuit 19 and with every clock phi1. Thus the output KO to the multiplier receives a logarithmic interpolation from KA to KB. |
