HELP-Maggie IIIa's are crackling at high frequency

Thanks for the reply David. When I hear the distortion it's during both CD and LP playback. Though I notice it more with a particular classical CD of various artists ironically. It could have been the amp/pre except it happened once before with another set up I had that included these speakers. The highs are pretty coarse distortion or not though. With the volume very low or with a mid tempo rock band it sounds perfect. I am using a broken in ultech audio CD player by the way

You could have a bad ribbon tweeter, (or two) and/or the wires have delaminated. The repair tech might not have gotten them completely glued down. It's a major ordeal to reglue the wires, I know, I've done it several times.

You could also have a crossover problem. Lots of things to check and troubleshoot...

sounds like teh tweeters are blown. Easy to replace if you contact Magnepan.

Admittedly I don't own or know anything about Maggies, so I am not adding to the advice already given. However, your OP doesn't say very much about the ARC gear other than the model numbers. I have a few thoughts about the ARC gear.

First, the V70 was first released in 1992 and actual power at clipping was 62 watts. Does the amp have enough power to drive the MG-IIIAs? That is, could you be clipping the amp? Is there an amp/speaker compatibility problem (e.g., wierd load)? Has the V70 been recently serviced? When were the tubes last replaced?

Second, the SP-6b was released in 1980, so the pre is getting up there in age. Same questions as with the V70 re: when last serviced and when were tubes last replaced?

your clipping your amp....