Noisy hum from Sony DCR-TRV230 from AV jack?
 

I am trying to backup VHS tapes, by using my JVC S7800U to play them, then transferring the video feed using a RCA (yellow/white/red) to 3.5 mm cable. I set my Sony camcorder to pass through, but the moment I plug in the 3.5mm cable into the yellow ID-2 A/V "in" jack on the camcorder, a notable "hiss" or "hum" can be heard. I am wondering how I can get rid of this. Is this a copyright protection signal?

Is the A/V cable the original Sony? If not, check the pin-out of the one you're using to see if it is correct. Sony & Canon used one standard but others (Samsung?) used a different one so not just any 3.5 mm cable will work.

Post a small sample video with the sound. Hiss and hum are very different noises! A little bit of hiss is normal for VHS linear audio. Is it possible that the audio is being recorded at a very low level and you're maxing the volume on your computer?

If it's a hum then maybe it's a ground loop issue. Make sure the VCR, camcorder and computer are all plugged into the same power strip in the same outlet.

It's not any form of copy protection.