Mellotronists

Hi guys - excuse the newbieness of this post, but I've just read
something that I'd like to know more on:

http://www.kleonard.com/mellotron/vt0304/pindertron3.htm

About 2/3 the way down this page, there's a comment made:  "Jerry
explained that the other Mellotrons have a built in equalization curve
to brighten up the higher end, but the Mike Pinder preamp does not."

Can you guys enlighten me as to what frequency the EQ curve starts? 
Am assuming it'll be a hi-shelf of some sort but am curious to know.

Thanks in advance,
dl