IIRC he needed to add the ES15 because he was getting weird artifacts when using the camcorder's line TBC + AVT-8710. He found that disabling the camcorder's line TBC resolved it, so he picked up an ES15 for line TBC duty.
But latreche34 makes a good point. Since you're changing your source to an S-VHS deck (assuming you get one with a built-in line TBC) you should first try eliminating the ES15 and go directly from the VCR to the AVT-8710. Only add the ES15 back in if the same issue appears, or if you aren't using a VCR with a built-in line TBC.
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I have captured lots of Hi8 tapes. All SP camcorder masters. Some have tearing/flagging, but not all. I only use the ES10 when necessary (while viewing a few minutes of footage to set light/dark levels I watch for tearing). Otherwise, I skip it and just use the camcorder line TBC. Use the exact same method for VHS.
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