there will be described below a preferred embodiment of the present invention with reference to the diagrams . the present invention is applied to a cd drive apparatus for a car in the following present embodiment . the cd drive apparatus has a function for , when a spindle motor is in rough servo , eliminating a high - frequency component from a ternary - controlled error signal , for example , by means of a low - pass filter and reducing resonance of the spindle motor . fig1 shows a structure of the cd drive apparatus according to the present embodiment . in fig1 the cd drive apparatus according to the present embodiment has : a disk 1 as an optical recording medium onto which a signal was recorded ; a pick - up 2 for reading the recorded signal from an information track of the disk 1 through a lens ( not shown ); a spindle motor 3 for rotating the disk 1 ; an rf signal generator 4 for amplifying the signal read by the pick - up 2 so as to efm - modulate the rf signal ; a signal extraction circuit 5 for extracting a frame synchronizing signal as a synchronizing signal from the efm - modulated rf signal ; a pll circuit 6 having an oscillator ( vco ) for synchronizing an output of the oscillator with the efm - modulated rf signal so as to extract a reproducing clock signal ; a divider 7 for dividing the reproducing clock signal outputted from the pll circuit 6 ; a first error signal generator 8 for comparing the divided reproducing clock signals with a reference clock signal so as to generate a phase error and speed error signals ; a first reference clock signal generator 9 for dividing a master clock , not shown , so as to generate a first reference clock ; a second error signal generator 10 for comparing the output from the signal extraction circuit 5 with the reference clock signal so as to generate a speed error signal ; a second reference clock signal generator 11 for dividing a master clock , not shown , so as to generate a second reference clock ; an equalizer 12 for shaping the error signal outputted from the first error signal generator 8 or the second error signal generator 10 so as to bring out the performance of servo ; and a driver 13 for outputting the output from the equalizer 12 as a signal which is capable of driving the motor . here , in fig1 the description about a flow of an audio signal modulation is omitted . however , an rf signal , which was efm - modulated by the rf generator 4 and error - correction coded by circ , is generated as a 16 - bit digital signal which was efm - modulated by a signal processor , not shown , and was error - correction decoded , and the 16 - bit digital signal is converted into an analog signal by a d / a converter , not shown . thereafter , the analog signal is allowed to pass an audible frequency zone by the low - pass filter , and a noise portion is eliminated so that an audio signal can be obtained . in the cd drive apparatus shown in fig1 a fine servo loop for executing fine servo is composed of the disk 1 , the pick - up 2 , the rf generator 4 , the pll circuit 6 , the divider 7 , the first error signal generator 8 , the equalizer 12 , the driver 13 and the spindle motor 3 . a rough servo loop for executing rough servo is composed of the disk 1 , the pick - up 2 , the rf generator 4 , the signal extraction circuit 5 , the second error signal generator 10 , the equalizer 12 , the driver 13 and the spindle motor 3 . further , the cd driver apparatus has switches sw 1 , sw 2 and sw 3 as switching means among the first error signal generator 8 , the second error signal generator 10 and the equalizer 12 . the switches sw 1 and sw 2 are in closed state when a lock signal outputted from the pll circuit 6 is high level . as a result , the fine servo loop is formed . at this time , the fine servo is executed . the switch sw 3 is in the opened state when the lock signal outputted from the pll circuit 6 is low level so that the rough servo loop is formed . at this time , the rough servo loop is formed . in addition , the signal ( information ) to be reproduced is recorded on the disk 1 as a bit sequence . when the reproduction of the information is carried out , the bit sequence is read as the reading signal by the pick - up 2 . in the bit sequence , the bit intervals are uniform and are predetermined . on the basis of these uniform bit intervals , the frequency of the reproduction clock is determined . furthermore , the bit sequence is divided into plural frames on the recording medium . each frame has the same length and a short bit sequence indicating a synchronization pattern is placed at the lead part of each frame . because each frame has the same length , the short bit sequences are located at equal intervals . on the basis of the short bit sequences , the frame synchronizing signal is generated . there will be described below operations of the fine servo and rough servo in the cd drive apparatus according to the present embodiment . at first , when a normal reproducing operation is performed on cd , the fine servo is executed . the oscillator ( vco ) which is capable of controlling an oscillation frequency by means of a voltage is provided in the pll circuit 6 , and the pll circuit 6 controls the oscillator so as to synchronize the efm - modulated rf signal outputted from the rf generator 4 with an output signal of the internal oscillator and obtain a predetermined reproducing clock signal . when the synchronization is realized , a high - level clock signal is outputted from the pll circuit 6 , and the switches sw 1 and sw 2 are closed . on the other hand , the reproducing clock signal outputted from the pll circuit 6 is divided into 1 / n by the divider 7 , and supplied to the first error signal generator 8 so as to be compared with a reference clock signal outputted from the reference clock signal generator 9 in the first error signal generator 8 . delay in phase of the reproducing clock signal from the reference clock signal is supplied as a phase error signal to the equalizer 12 via the switch sw 1 , and delay in frequency of the reproducing clock signal from the reference clock signal is supplied as a speed error signal to the equalizer 12 via the switch sw 2 . examples of the phase error signal and the speed error signal outputted from the first error signal generator are shown in fig2 . as shown in fig2 the phase error signal and the speed error signal become signals which are outputted in proportion to a difference in phase ( rad ) or a difference in speed ( v ). the equalizer 12 has amplifiers 20 and 21 , an adder 22 , a first low - pass filter 23 and an amplifier 24 . the phase error signal and the speed error signal supplied via the switches sw 1 and sw 2 are added to each other by the adder 22 via the amplifiers 20 and 21 so as to be supplied to the first low - pass filter 23 . here , an input of the adder 22 is connected with one of the amplifiers 21 and an amplifier 26 by a switch sw 4 . when the lock signal is high level , the adder 22 is connected with the amplifier 21 , and thus the speed error signal is supplied to the adder 22 via the amplifier 21 . the first low - pass filter 23 whose cut - off frequency is set to a several hundreds hz ( for example , 500 to 1000 hz , preferably , 500 to 700 hz ) extracts a frequency component suitable for the spindle servo . the signal extracted in such a manner is outputted to the driver 13 via the amplifier 24 . the driver 13 outputs the output signal from the equalizer 12 as a signal which is capable of driving the spindle motor 3 . as a result , the rotation of the spindle motor 3 is controlled so that the delay in phase and delay in speed are corrected . the velocity of the cd is controlled constantly and accurately within a range of 200 to 500 rpm by the fine servo in the fine servo loop , and the satisfactory reproducing operation is performed . there will be described below the rough servo . as mentioned above , the rough servo is executed when the lock signal outputted from the pll circuit 6 becomes low level . for example , at the time of starting the apparatus , during a search operation , during a track jump operation , or during a leading - in process to the normal spindle servo just before the reproducing operation , the lock signal is switched into low level , and the switches sw 1 and sw 2 are opened and the switch sw 3 is closed . as a result , the output of the second error signal generator 10 is supplied to the equalizer 12 via the switch sw 3 . the signal supplied to the second error signal generator 10 is a frame synchronizing signal which was extracted by the signal extraction circuit 5 . a synchronizing signal is included in each frame of the efm - modulated rf signal outputted from the rf generator 4 , and the signal extraction circuit 5 extracts only the synchronizing signal from the efm - modulated rf signal , and extracts a frame synchronizing signal having a square shaped waveform by comparison with a predetermined threshold value . in the second error signal generator 10 , the frame synchronizing signal is compared with the reference clock signal outputted from the reference clock signal generator 11 , and delay in frequency of the frame synchronizing signal from the reference clock signal is supplied as a speed error signal to the equalizer 12 via the switch sw 3 . at this time , the speed error signal outputted from the second error signal generator 10 , as shown in fig3 ( b ), becomes a ternary controlled signal . for example , as shown in fig3 ( a ), in the case where a pulse width t 1 of the frame synchronizing signal is longer than a pulse width of the reference clock , as shown in fig3 ( b ), an accelerating pulse signal of pulse width t 2 is outputted . moreover , when a period t 3 is a pulse width which is equal with the pulse width of the reference clock , the output becomes zero . further , since a pulse width t 5 is shorter than the pulse width of the reference clock signal , a reduced speed pulse of pulse width t 6 is outputted . the equalizer 12 has the amplifiers 20 and 21 , the adder 22 , the first low - pass filter 23 and the amplifier 24 as well as a second low - pass filter 25 and an amplifier 26 shown in fig1 . the ternary controlled speed error signal supplied via the switch sw 3 is supplied to the second low - pass filter 25 . a cut - off frequency of the second low - pass filter 25 is set to several dozens to several hundreds hz ( for example , 20 to 500 hz , preferably , 20 to 200 hz ). the second low - pass filter 25 cuts a high - frequency component of the ternary controlled speed error signal shown in fig4 ( a ), and outputs a speed error signal shown in fig4 ( b ) which changes comparatively gradually . the speed error signal is supplied to the adder 22 via the switch sw 4 which is switched to the amplifier 26 side by the lock signal switched to low level . at this time , since the switch sw 1 is opened , the signal is supplied to the first low - pass filter 23 without performing the signal adding operation . since the cut - off frequency is set to several hundreds hz in the first low - pass filter 23 as mentioned above , the signal which passed through the second low - pass filter 25 directly passes through the first low - pass filter 23 so as to be supplied to the driver 13 via the amplifier 24 . therefore , the ternary controlled speed error signal , whose high - frequency component is eliminated and which changes comparatively gradually , is supplied to the driver 13 as shown in fig4 ( b ). for this reason , the resonance of the spindle motor 3 can be reduced more greatly than the conventional apparatus , and thus oscillation of the disk 1 can be reduced greatly . therefore , generation of a resonance waveform in the tracking error signal can be reduced greatly , and thus accurate tracking jump control or tracking servo control is made . the present embodiment described the example that the switch sw 4 is provided between the amplifier 21 and the adder 22 , but since the second low - pass filter 25 has a cut - off frequency lower than that of the first low - pass filter 23 , the switch sw 4 may be provided between the first low - pass filter 23 and the amplifier 24 . the above - mentioned effect of the present invention can be clarified further by comparison with the conventional apparatus . fig5 is a block diagram showing a structure of the conventional drive apparatus . here , the same reference numerals are given to the parts identical to those in the drive apparatus of the present invention shown in fig1 and the description thereof is omitted . as shown in fig5 since in the conventional drive apparatus , the equalizer 12 is not provided with the second low - pass filter 25 , the amplifier 26 and the switch sw 4 , the ternary controlled speed error signal shown in fig4 ( a ) outputted from the second error signal generator 10 is supplied directly to the driver 13 via the amplifier 21 , the low - pass filter 23 and the amplifier 24 at the time of the rough servo . as a result , the high - frequency component included in the ternary controlled speed error signal causes unnecessary oscillation of the spindle motor 3 , and the shaft of the spindle motor 3 is resonated , and thus the resonance peculiar to the spindle motor 3 is caused . since the resonance oscillates the disk 1 mainly in the horizontal direction , its signal becomes disturbance and it appears as a resonance waveform in the waveform of the tracking error signal . as a result , there is a problem that a bad influence is exerted on the track jump control or tracking servo control . also in the conventional drive apparatus , the equalizer 12 is provided with the low - pass filter 23 , but the low - pass filter 23 is set so as to have a cut - off frequency of several hundreds hz in order to obtain general property required for constant speed control of the spindle motor 3 . as a result , the high - frequency component included in the signal shown in fig4 ( a ) cannot be eliminated , and thus the above - mentioned resonance of the spindle motor 3 cannot be prevented . in addition , in order to prevent the resonance of the spindle motor 3 , a low - pass filter , which sets the cut - off frequency of the ternary controlled speed error signal within the range of several dozens hz to several hundred hz , is required , but if such a low - pass filter is provided in the position of the first low - pass filter 23 , satisfactory servo property cannot be obtained . on the contrary , in the drive apparatus of the present embodiment , as mentioned above , the equalizer 12 has the first low - pass filter 23 having a cut - off frequency of several hundreds hz and the second low - pass filter 25 having a cut - off frequency of several dozens to several hundreds hz . at the time of the fine servo , the first low - pass filter 23 having the cut - off frequency of several hundreds hz is used to make the servo control so that the satisfactory servo property can be obtained . moreover , at the time of rough servo , the second low - pass filter 25 having the cut - off frequency of several dozens to several hundreds hz is used so as to make the servo control , and the occurrence of the resonance of the spindle motor 3 can be reduced greatly . herein , the present invention is effective in the case that a motor with a brush is used as the spindle motor and also in the case that a motor without a brush is used . in addition , the present embodiment described the example that the ternary controlled signal is used as the error signal outputted from the second error signal generator 10 at the time of rough servo , but the present invention is not limited to such a structure , and thus it is effective in another multi - value controlled signal . in addition , the drive apparatus of the present embodiment is the example that the present invention is applied to a single - speed drive apparatus , but the present invention is not limited to such a structure . for example , in a n - speed drive apparatus , a frequency of the speed error signal outputted from the second error signal generator becomes high , and thus the cut - off frequency of the second low - pass filter 25 may be set to the same value as the frequency in the above - mentioned embodiment , or to a suitably higher frequency according to the frequency of the speed error signal . in addition , the drive apparatus of the present embodiment is the example that the present invention is applied to a cd drive apparatus , but the present invention is not limited to this , and thus can be applied to drive apparatuses for cd - rom , cd - r , cd - r / w , dvd , dvd - ram and dvd - rom . the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof . the present embodiments are therefore to be considered in all respects as illustrative and not restrictive , the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein . the entire disclosure of japanese patent application no . 10 - 330021 filed on nov . 19 , 1998 including the specification , claims , drawings and summary is incorporated herein by reference in its entirety .