Well, 78/33 is 2.36 so 10kHz on the LP will become 23.6kHz when played at 78 rpm, and 15kHz becomes 35.5 kHz.  Are you sure your cartridge is good at those frequencies?  Also, the turnover and rolloff frequencies on your preamp will be working on the wrong frequencies when the LP is played at 78.  This would require special turnover and rolloff playback compensation for the slowed down playback.
What are you transferring it to and how will you slow it down?

Ron Roscoe

-----Original Message-----
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of 6295LARGE .
Sent: Wednesday, August 09, 2017 1:15 PM
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Subject: [ARSCLIST] Transferring LPs at 78 RPM

Hello everyone

If I transfer a vinyl LP at 78 RPM then slow it down to proper speed do I lose anything?

Regards,
Ben Roth