Does it make the same noise when its in the plinth? I think they have a spring suspension.Anyhow,when some TT's are run on something solid instead of floating on the springs, the motor does amplify itself for some reason.If you could,try lifting it up of off the saw horses if you don't have the original plinth with the spring suspension,and see if it quiets down.Of course if it does it in the original plinth,then this wouldn't apply.The idler wheel may be hard,or some other rubber parts mentioned above.