| 摘要 |
In a tape recorder with an AC bias generator 6, a dynamic bias optimisation is achieved in that the combined bias and audio signal at the sound head 2 is taken to a high- pass filter 10, whose output signal across a comparator 12 is used to control the current strength of the bias impressed from the generator 6, whereupon this is controllable in a well-controlled manner by means of its own regulating circuit 10, 12, 6. The invention is built on the fact that the audio signal content of high audio frequencies functions as an effective bias for the lower audio frequencies, and in just this fashion one can achieve a dynamic optimisation by controlling the supplied bias as a function of the total active bias making use of a feedback control loop. In this way, it is especially possible to hold the total active bias constant, which is advantageous for full utilisation of the recording capability of conventional audio tape. Furthermore, the strength of the total active bias can easily be adjusted and optimised for different types of tape in that one can establish during the adjustment process a larger or smaller level for the variable bias furnished by the generator 6 at the feedback control loop. <IMAGE>
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