I've only had this pre for a few days now (got it S/H no instuctions).. I was doing a quick mini shootout between the 201S, my mackie desk pre's and my RBI.. I only gave the Demeter about 1.5 min warmup time and pluged into the jensen balanced XLR on the back... As I was playing through it I heard some crackly type sounds (sounded like a scratch pot).. Is this because the tubes are not warm yet? I've left it on now for about 10 min and the problem is gone... how long do you guys let these puppies warm up for?? ps.. ithe 201S KILLED the mackie and the RBI tone wise.... the RBI was mid scooped, hyped and very compressed sounding (blend @ 2 o'clock), the mackie was punchier in the mids but when I switched to the Demeter the mackie sounded like there was a pillow over it.. the top end definition on the Demeter is awesome.. also much more controlled bass and low mids.. the mackie "wooled out" easier... the 201S is a v ery hifi pre with great articulaton.