Left channel much louder than right?

It is probably due to improper compensating forces to offset the cartridges natural desire to drift to the outside of the groove. As I recall your arm doesn't have built in anti skating compensation but the manufacture does have sugestions for doing something, like twisting the phono leads or something. It is also possible that you would over come much of this by increasing the VTF to the manufacturer's max spec.

If the azimuth of the cartridge is off this can happen too. Basically what I mean is that the cartridge is not sitting perfectly perpendicular to the LP, it's tilted to one side or the other.

I'm not familiar at with the JMW9 arm - but I'm sure there's a way to adjust it. I'm sure someone out there will chime in with the necessary instructions and to correct me on correct terminology for this setting - I just can't recall what it is other than to call it the azimuth setting.

You say you know that it's not a tube or interconnect. How do you know it's not the ics?

I encountered a similar problem at the same time I purchased new preamp. Therefore, I swore it was the preamp.

But then after performing a series of tests with the ic's (crossing L&R from source to pre, then from pre to amp, etc), I was able to determine that it was the right channel ic from the source to the pre that was the culprit.

The mfg'erer confirmed the problem and replaced the cables the one pair of cables. Problem fixed.

-IMO

make shure the cart connected properly.

I would suspect the cartridge itelf, or the wires in the arm. Incorrect setup (angles and forces) will make it sound lousy, but, in my experience, have little effect on loudness.

Try swaping channel connections at the cartridge.