MAC Autoformers?

The Eminent Technology LFT-8b, while employing magnetic-planar drivers as do Magneplanars, is rated as 8 ohms by it’s designer, Bruce Thigpen. While Maggies’ impedances are solidly in the 3-4 ohm range, the ET LFT driver is an almost purely resistive 11 ohm load (the speaker’s 8 ohm rating a consequence of it’s dynamic woofer, for frequencies 180Hz down).

Maggies require a LOT of power, very expensive in a tube amp. The matter is exasperated by their 3-4 ohm load, almost all tube amps putting out half as much power there as at 8 ohms (the notable exception being Music Reference/Ram Tube’s Roger Modeski’s RM-200---100w/ch @ both 8 and 4 ohms!). If you bi-amp the ET LFT-8b, you can use a modestly-powered tube amp (the RM-200 works splendidly, as I have heard does the Atma-Sphere M60) on the m-p drivers, and a ss amp on the woofer. The panels and the woofers each have their own binding posts.

I posted this on the thread Roger (ramtubes) started to discuss transformers, but thought I would do it here as well.

Roger gave a 90 minute talk on tube amp design at the 2015 Burning Amp Festival. If you own a tube amp, or are thinking of getting one, you will be glad you watched the video. The video is on You Tube, but also on the Berkeley Hi Fi School website.

Go to "berkeleyhifischool.com" and put your browser over "RESOURCES". A drop-down screen will appear---click on "VIDEOS". On the right hand side of the page is a row of "ARCHIVES". Click on October 2015, and the video will appear. Prepare to learn a lot!

I know BIF, Roger doesn’t look any different than a regular guy, but damn! It’s humbling to listen to him talk about amplifier design; I wonder how anyone can have so much knowledge in a normal-sized head. I talked to Bill Johnson a few times, and to Tim de Paravicini (EAR-Yoshino), David Manley, Keith Herron, Ralph Karsten, Frank Van Alstine, Max Townshend, and numerous other really good Hi-Fi engineers. They are all very interesting of course, but I have the distinct impression that Roger Modjeski understands amplifier design as well as any human in history. That he and his products aren’t more well known and widely owned actually doesn’t surprise me any more than the fact that most of my favorite music is made by artists known to only the hardest-core music lovers, like we here on AudiogoN.

The late Brooks Berdan was my Hi-Fi dealer for many years. He sold me Hi-Fi, I sold him vintage drums. He was a Music Reference dealer, and loved Roger and his amps. He told me his wealthier clients would pass up MR products because they didn’t cost enough (no bragging rights), or weren’t being reviewed or talked about enough in TAS and Stereophile, didn’t have the High End cashe’ of ARC, VTL, Jadis (Brooks sold a lot of Jadis), etc. Brooks had a LOT of used ARC amps in his pre-owned racks, their owners tired of the breakdowns, repairs, frequent tube replacement, updates, etc. His tech Tom Carione showed me all the burned circuit boards in the ARC amps he had repaired every time a tube blew. He had never seen a Music Reference amp come back for repairs---never. That’s my kinda amp!---Eric.

Speaking of Richard and Roger, Roger says the idea to install the Capacitor "Forming" function into the MK.2 version of his Music Reference RM-200 amp was a suggestion from Richard. Brooks Berdan sold a lot of RM-9's and RM-200's to owners of Vandersteen 2's and 3's, a great matchup.

For the price of retubing an ARC Reference 150, you can just about buy a used RM-200! The four output tubes run in the RM-200 (producing 100w/ch) last about five times longer than those in the REF 150. How many 150 owners have compared their amp to the RM-200? I’m guessing none. You can buy a used PAIR of RM-200’s for less than a single used Ref 75! There’s one on AudiogoN right now for less than $3k, a ridiculously good deal. I have all the power I need from the one I already own or I’d buy it.