[quote author="sismofyt"]I second that. I always thought Millenias Twin Topo was a sales trick :roll:[/quote]
No trick. Twin Topology is two separate, selectable amplifier topologies. One topology is a transformless 350V vacuum tube amplifier. The other topology is a transformerless discrete solid-state amplifier. In most cases, the amplifiers are biased Class A.
The functional stages, such as opto-resistive elements or active filters, are shared in common by both amplifier stages. Fred (who I see is a regular around here) did the original TT circuit design circa 1997-1999, which includes the NSEQ-2, TCL-2, and most of the STT-1 Origin. Fred did a great job for Millennia, and I see he continues to design fine circuits. Fred makes note of his work for Millennia on his website:
http://www.forsselltech.com/forssell-MM.htm
The "Twin Topology" idea is not mine. To my knowledge, the TT concept was first introduced in the mid-1990's by Bruel & Kjaer with their type 4040 microphone. This microphone has both a Class A biased vacuum tube head amplifier and a Class A biased FET solid state head amplifier
in the same mic body. An engineer selects FET or tube electronics, depending on the artistic or sonic goals. Type "4040" in their search engine:
http://www.dpamicrophones.com/
I remember seeing the prototype 4040 at an AES show (1994?) and thinking ?what a great idea for a mic preamp.? Some years later, I was talking with Wyn Morro who said that he was ?working on an EQ with tube and solid state signal paths and I?m going to charge $15,000 for it!!? Between Wyn and DPA, I became inspired to create our own version of parallel amplifier products, including mic preamps, EQ?s, and dynamics.
More recently, we?ve developed a product called the TD-1 ? a half-rack recording channel with Twin Topology instrument amplifiers (vacuum tube or discrete FET). In fact, we learned this week that the TD-1 was nominated for a 2004 TEC Award! You can see how the TT amplifiers are implemented in TD-1 here:
http://www.mil-media.com/pdf/td1-block-diagram.pdf
We?re also working on some other TT product ideas, but I?m not going to talk about those yet
. I think David Bock did a good job of explaining the multi-topology concept from a mic makers perspective. I hope this clarifies ?Twin Topology? design and sheds some light on the subject. If you have other questions, I would be happy to address them.
By the way, I think this is probably the most on-target chat room in pro audio.
Best wishes,