75µS to 50uS Pre-Emp

[folkeu08]

Hi,
What change to adapt this pre-emp 75µS to 50µS :



Thanks

[reverend]

cir_rfv007.jpg

In theory (though I haven't tested this), changing the 330pF capacitors circled in red with 220pF ones should do the job.

Rev

[Albert H]

The Rev is exactly right. Use accurate 220pF capacitors (not cheap ceramic ones), and be careful in setting up the HF clipper - it's easy to overdo it! It's also worth using slightly lower frequency filters (16 kHz is getting a bit too close to the 19 kHz stereo pilot). My filters use "gyrator" networks (to emulate inductors), and go over like a cliff at 15.15 kHz. By 19 kHz, they're around 74 dB down.