Too much gain is your problem as Al states, Rothwells attenuator plugs work but they can also create impedance matching issues.
Looks to me like the alps VC pot is on the output RCA's on this pre, and there is a tube gain stage before it.
The best bet is to either get the tube stage gain reduced that's before the alps pot by a tube tech, or sell and get a passive preamp with a logarithmic 10k pot.
7th and 6th last pic
[url]http://www.wiredstate.com/forum/viewtopic.php?f=36&t=14853&start=200[/url]
Cheers George