Fostex X-24 User Manual download pdf (Page 12)

X-24

3-13. Overall Frequency Response Adjustment

Set the controls under the same condition as 3.12 except the DOLBY switch. (The switch should be turned on.)

Apply a 400 Hz, -35 dBV (18 mV) signal to the INPUT 1 and 2 phone jacks.

Record the signal, rewind and playback the recorded section of the tape and memorize the output level at TAPE

OUT 1 ~ 4.

Next, apply 6 kHz & 12 kHz, -35 dBV (18 mV) signals to the INPUT 1 and 2 phone jacks.

Record the signal, rewind and playback the recorded section of the tape.

Check if the 6 kHz / 12 kHz output level at TAPE OUT 1 ~ 4 is within ± 2 dB comparing to the 400 Hz output level.

If the AC volt meter reading is not within the above specification, adjust the pot R133 ~ 433 (220 kΩ) on the R/P

AMP PCB assy so that the recording level at 6 kHz will be within the specification.

3-14. T.H.D. Measurement

Connect a distortion meter, 400 Hz HPF and 30 kHz LPF to TAPE OUT 1 ~ 4 and set the controls under the same

condition as 3-12.

Record a 1 kHz, -10 dBV (0.3 V) sine wave signal.

Playback the recorded part and check if the distortion level is less than 2 %.

3-15. Erasure Measurement

Connect a 1 kHz bandpass filter and AC volt meter to TAPE OUT 1 ~ 4 and set the controls under the same

condition as 3-12.

Record a 1 kHz, 0 dBV (1 V) sine wave signal which is 10 dB higher than the reference recording level on a blank

tape.

Rewind the tape to the start point of recording and advance it by a short length. Then, record again without

applying the signal on the remaining part.

Rewind the tape to the start point again and play it back. Check if the level ratio between the playback level and no-

signal section (erased part) is 67 dB or more.

3-16. Cross Erasure Measurement

Set the controls as follow.

Trim knob: At minimum

Input fader: Standard position (At 8 ± 1)

Dolby B noise reduction on/off switch: OFF

Input a 100 kHz, -10 dBV signal to the INPUT 1 and 2 phone jacks and record the signal on all tracks.

Rewind the tape to the start point of recording. Then, erase the 10 kHz signal on the track and check if the level

difference at the corresponding track indicated below is within 1 dB.

Tracks to be measured Track (s) to be erased

2 1 and 3

3 2 and 4

If the level goes down by more than 1 dB, check the tape running path again.

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 ... 25 26

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Fostex X-24 User Manual Page 12