There is nothing wrong with the L07J tonearm on the L07D, except that it is a bit dated when you look at it now. What does hurt the sonics is the Litz tonearm wiring and the fact that the plug by which the Kenwood phono cable engages the base of the L07J tonearm is or seems to be a one-off, in that I and others have found no plug that can replace it. Hence, many including me have stuck with the OEM cable which in my opinion is a slug. I tried once to take apart the tonearm in order to direct wire it to my phono stage, but I got to a point where I feared I would damage the tonearm and so gave it up. Suffice to say I think the Kenwood Litz cable is a shortcoming (sounds very Cardas-like but in a bad way, IMO), I would instead use the optional outboard tonearm mount for a second tonearm to adapt a modern high end arm for use on the L07D. (That’s what I have done.). But I don’t think the L07J tonearm is at all the problem; it’s that oddball plug and the cable that it feeds.
Dover, thanks for correcting me on the Beat vs the Wave Kinetics (the name of which I could not recall). I don’t know why you are so up in arms over the fact that I like Steve Dobbins’ work, in the sense that I don't find it ugly. Moreover, looks mean virtually nothing to me when it comes to assessing audio equipment. In fact, I think I am rather partial to gear that decidedly lacks bling. About 15 years ago at the Rocky Mountain Audio Fest, I listened late into the night to the Beat in Steve Dobbins’ room, because it sported a cartridge I was then interested in. Steve was very nice about letting me sit there an just listen. I never heard or saw the Wave Kinetics, but I did carry the erroneous idea that it was the one with no servo feedback.

