Mongoose was one of the leading high-end brands back in the day and had a number of bonded frames with mixed construction... carbon/aluminium, steel/carbon, steel/al, ti/steel, etc. Them and Miyata really liked doing mixed-bonded setups. As to the amplifier... Mongoose commissioned Horst Leitner to design them a full suspension bike, after they saw some of his early work at a trade show (Amp B-1), and the Mongoose Amplifier was the result. They were all made by horst in his factory, and were essentially identical to the Amp B-2 frames. After problems with racers using them for DH and yanking the headtubes off from the dual-downtubes when casing jumps or crashing, they went to a single downtube in 1995 and thus the B-2 design was replaced by the B-3 (the mongoose version was labeled Amplifier 2). Mongoose also had the Amp F-1 forks on the amplifiers, and the only way you got them was buying the framesets (frame/fork) and building them up yourself. They didn't sell complete amplifiers till the 95 model year.
Univega also had Amp making them versions of the Amp F-1 forks, called the Univega Concept fork, and was using them on their higher end models. And Amp history doesn't end there... a couple dozen other brands either had complete Amp frames made for them, or purchased just the rear ends to mate to their own front ends (Rocky Mountain, Dagger, etc) or otherwise copied (often without licensing, coughGTcough) the horst-link rear end which is what made them a viable design. I think its in a 1994 MBA article they tested FIVE mac-strut bikes... Supergo's Access FS version (taiwan made licensed copy of an Amp), Amp's B-2, Rocky Mountain's Edge, Battle's Tomahawk, and I think the fifth was a Proflex design which was the only mac-strut that wasn't an Amp clone.
Mac-struts refers to the intergrating of the shock to the seatstay without a pivot between them. You'd find them on bikes both with horst-links and without (seatstay links). They were popular because they were simple to understand for the consumer, and by borrowing a car suspension term, made it seem like the idea of full suspension was more refined than it really was at the time, so easier to seperate consumer from contents of wallet.
