What do defective phono tubes sound like?

Jloveys, the static discharge was likely not been 'seen' by the cartridge. Its often a discharge between the ungrounded arm and the turntable. So no worries!

Sirspeedy, your description of the problem sounds like a static discharge to me. If the arm is improperly grounded it is possible for it to *not* hum, but have discharge problems, especially with low humidity. The needle tracking the LP will create the static charge and if not drained off by the grounded arm, you will get a random static 'pop', which can be quite loud once amplified by your electronics!

A hint is that this problem showed up when you changed arms. If the prior arm is available, I would swap it in and see if that sorts it out. If not, I would test the arm to see if it is really grounded correctly. BTW the turntable should be grounded to the arm too. If not, that can cause static discharge too.

I would check for continuity between the ground of the table and the chassis ground of the preamp.

Sirspeedy, I would be suspicious that the CD player is making either RF, DC or both. I'd pull it out of the system altogether, as if it is RF, well, that stuff can get in everywhere!

Given what you have told me its *not* the tone arm that did that.

Alternatively, your preamp could have been giving you fits all along, with the symptom masquerading as something else. First thing I would do would be to run the system with no digital at all and see if it works. If yes, let it play and see if it still pops. If not, then you need to see if the amps/speakers are OK. If they are, then you need to talk to the manufacturer about the preamp.