Yo Taxman! Yeah, that's annoying. The product archive for the tripower series is auf Deutsch (in German) only. The discontinued tripower series was introduced in the early 1990's, and uses a Neodymium/Boron rare earth magnet. The D3900 is a hypercardioid handheld stage vocal mic designed for maximum gain before feedback. It never caught on much in the US. I own a pair of D3800's, which is the same mic without the recessed bass cut and presence boost switches. They were basically $300 mics in the 1990's, and can now be found new in the flight case for around $100, which is a hell of a deal.
The triangular body shape was intended to make them more comfortable to hold, and there is an accessory wireless transmitter (sold separately) which attaches to the XLR connector and matches the triangular body shape. Here's a review of the series from 1992:
http://www.trubitt.com/akg_tri.html
My impression of the mic is that it is real clear and detailed (the upside) and rather unforgiving (the downside). The hypercardioid polar pattern and its high output result in a proximity field which is abrupt and aggressive. In short, it is a *great* vocal mic for somebody that really knows how to maintain a constant distance from the mic. Someone who moves a lot will struggle with this mic. For these reasons, it is my go-to stage mic for standup piano, which can be counted on not to move much. It is good on clean cabs, percussion, or anything else that doesn't move much. Its clarity and detail are stunning, which makes it sound more like a condenser than a dynamic.
In short, I consider it as a real cool specialty mic that is now wildly underpriced. I can't comment much on the effects of the switches, as my mics don't have them, but the review above gives the impressions of the testers. All I can say is: 1. don't sell it- when you find out what it's good for, it's a great mic.- and 2. Find the right distance, whatever it is for you, and *don't move*!-Richie
