Filter category from rss but not from individual category rss

Hi

I found this little trick

function filter_feed($query) {
if ($query->is_feed) {
$query->set(‘cat’,’-688′);
}
return $query;
}

add_filter(‘pre_get_posts’,’filter_feed’);

for functions.php

So a category (in this case 688) it’s filtered from rss

My question it’s if it’s possible to filter from

domain.com/rss

but on

domain.com/category/rss

continue working

Any idas?

Thanks in advance