I speedballed my Crack a week ago.
I installed a new pot (TKD 2CP-601) a week before that.
After installing the Speedball there has been a slight scratching noise when adjusting the volume on the Crack.
It's barely noticeable on my HD6XX Senns (but much more prominent on my 80 Ohm Beyer DT770s)
Some observations:
The scratching is not constant; only slight stabs of scratching when I twist the pot,
the quicker I twist the louder the scratch,
it goes away after a while.
Is this expected behaviour or indicative of some malady?
Just to go off topic right off the bat:
After speedballing, my 80 Ohm Beyers really stopped playing nice with the Crack.
I notice the bass seemingly dropping off sometimes, like the headphones can't keep up.
This does not happen with the 300 Ohm Senns.