Does anyone care to ask an amplifier designer a technical question? My door is open.

Roger, here’s a question about light loading with the RM-200 Mk.2 amp: With a loudspeaker given a nominal 8 ohm load rating by it’s designer/manufacturer (it measures between 10 and 20 ohms from 20Hz to 20kHz save for the 60Hz-180Hz band, where it dips down to 7 ohms, centered at 80Hz), the RM-200 will of course put out at least it’s rated 100w/ch when connected to the amp’s 8 ohm taps. If it is instead connected to the 4 ohm taps (light loading), what will the amp’s output wattage be?

Because of the speaker’s relatively high and even impedance curve, it is not for the flattest frequency response I am interested, but rather the lowest distortion and longest tube life. I realize that with light loading those will be achieved at the cost of less power output from the amp. I have a modestly-sized room, and don’t listen at very high SPL, so am willing and able to accept that.

John Lennon: "All I want is the truth, just give me some truth".

Amen, brother! "High End" reviewers like Harry Pearson convinced lots of audiophiles that the measured performance of an amplifier and that amp’s sound are unrelated. That making a "good" sounding amp was more art than science. Yes, the race for as-low-as-possible static-measured distortion did lead to bad audio engineering, but good designers understand that, and perform bench tests that reveal the dynamic behavior of their designs.

I can’t count the number of times I have heard an audiophile (or even hi-fi retailer), when presented with evidence of the poor engineering of a component the audiophile likes (or the retailer sells), or worse owns, defend that component by saying something like "Well, it’s the sound that matters". If a poor design, showing obvious performance weaknesses, sounds "good", something is very wrong somewhere.

@krelldreams, though you asked Roger for a recommendation of a low-powered tube amp for use with Maggies, I hope he doesn’t mind if I chime in on the question. As a long-time Maggie owner (my first bought in 1973, the original Tympani T-I; I now own Tympani T-IVa’s), I can assure you a typical low-powered tube amp is about the worst kind you can partner with a Maggie. But what do you consider a "lower" powered tube amp? Under a hundred watts? Under 50? Maggies are very insensitive speakers, and benefit from a "higher"-powered amp. Another factor working against tube amps with Maggies is that the speaker present a 4 ohm and lower load to an amp, and almost all tube amps prefer a higher-impedance load, producing less power at higher distortion into lower impedances than into higher.

While this may strike some as inappropriate in an answer to a question posed to the designer/manufacturer of Music Reference amps, I’m doing it anyway ;-) . There is one tube amp I can suggest for use with Maggies, the one I use: the Music Reference RM-200 Mk.2. Unique amongst tube amps, it produces slightly higher, not lower, power into a 4 ohm load than into an 8 ohm one. About 100 watts/ch into 8 ohms, a little more into 4. Most 100w tube amps produce only 60 or so watts into 4 ohms. The RM-200 is also a real good amp in general terms. Low distortion ("clean" sound, including at bass frequencies, The Achilles heel of many tube amps), low output impedance (no tube amp colorations, such as added "warmth" and/or "soft" highs), stable into reactive loads (usable with ESL’s and ribbons), long tube life (some popular tube amps burn through a set of output tubes in as little as a couple thousand hours, and a replacement set are not cheap), and tasteful, classic styling, all at a reasonable price. Review, both subjective and objective, available on the Stereophile website.

@ramtubes, Roger I happened to make my first visit to a new hi-fi shop just opening in Livermore, CA in 1973, Audio Arts. It was a 1-man shop, that man being Walter Davies, now the maker of the great Last Record Care products. And as luck would have it, that was the same day Bill Johnson was delivering and installing a complete ARC system in his new dealer Walt’s listening room; a Thorens TD-125 MK.2, a Decca Blue mounted on a prototype ARC arm (it never went into production), an ARC SP-3, and Tympani T-I’s (as you said, at the time distributed by ARC) bi-amped with a D75 and D51.

I was just a kid, and spent a couple of hours getting an education in high end hi-fi. A couple of months later I had that exact system (with a Decca arm) in my own room. All set up and connected, I pushed in the power switch on my SP-3, and immediately heard a "poof" and smelled the aroma of something burning, which turned out to be a resistor in the power supply. Welcome to the wonderful world of using under-rated parts! High End? Not by my definition!

Roger, funny you mention the Fulton J, as that was what I replaced my Tympanis with! After having lived with the T-I’s for a year, in ’74 I heard the Model J at John Garland Audio in San Jose, powered by Fulton’s own mono tube amps (a modified Dynaco Mark III, I believe). I had heard ESL tweeters before (in the ESS Transtatic I---they had used the same RTR tweeters as did Fulton in the J, 3 of them to the 6 in the J), and the Infinity Servo-Statics, and those tweeters made the Tympanis sound SO veiled. I also was hearing and feeling the bottom octave, which was missing in the Tympanis. The J’s midrange (provided by the available-separately Model 80) was great by itself (unusually transparent for a cone speaker), but adding the RTR ESL tweeters and Fulton’s transmissionline-loaded woofer box made it a very full range loudspeaker. I no longer have the Fultons, but I picked up a pair of Transtatics in 1982 for 400 bucks.

Bob Fulton was also a great recording engineer, and his ARK label LP’s are fantastic; very alive (immediacy, like a Decca/London cartridge), transparent, and detailed, with extremely natural vocal and instrumental timbres. He recorded local Minnesota choirs and orchestras, which in their amateurishness are charming.

@krelldreams, you should definitely try your Dynaco ST70 with the MG1.7, just to see if that gives you enough power. The RM-10 is a far better amp than the ST70, but their power output is about the same (right Roger?). But remember, a 35 watt tube amp puts out less power at the Maggies’ 4 ohm (and lower) impedance. The RM-200 doesn’t.

Another option is to have Roger make you an autoformer (maybe even build it into the amp!), to raise the impedance the RM-10 sees.

Yow, things are warming up around here ;-) . I like opinionated people, it requires and reveals passion. That’s true even if I see things differently; no two people agree on everything, and everyone develops their own priorities and tastes in music and it’s reproduction. I, not being an engineer, love reading about hi-fi design by those who are, and find discussions of design philosophy and styles very intellectually stimulating.

Like many Americans, on Thanksgiving day my assembled family expressed, member by member, what they are thankful for. I’m thankful for having Ralph, Roger, and all the passionate Audiogon music and hi-fi enthusiasts contributing to this forum!

@ramtubes, I finally got around to reading the review by Herb Reichert of the Cary SLI-100 in the December Stereophile. Damn, what a piece of junk! Cary specs the amp at 100w/ch from a pair of KT150 power tubes per channel; John Atkinson, using 1% THD and noise as the definition of clipping, measured the amp’s output from the 8 ohm tap into an 8 ohm load as a mere 3.2 watts! Out of a pair of KT150’s! You have to work REALLY hard to make an amplifier that bad. Whomever designed this boat anchor should find a new line of work; amplifier design is obviously beyond his abilities. 3.2 watts/ch for $5995? Not a "very good value" ;-) .

And what does this tell us about Herb Reichert, who very much likes the sound the amp produces? That Herb apparently likes distortion, I would say. You are now justified in completely disregarding anything and everything Reichert has to say about hi-fi. If one "likes" a power amp this bad, what doesn’t one like?

RM: "He (Harry Pearson) was an idiot." At an instore talk in the 1980’s at a S. California hi-fi shop to introduce a new product, Bill Johnson told this story about Pearson: Bill had sent Harry a new pre-amp for evaluation and review, and soon received a call from HP, saying the pre was defective. Bill had Pearson return the pre to ARC, where it was tested and found to be operating perfectly. A phone call and questions revealed the source of the problem; Harry had installed shorting plugs, not into the pre’s unused input jacks, as they are intended to be used, but into it’s output jacks. Well duh! Should anyone that ignorant really be considered a "reviewer", and empowered as such?

When the ARC SP--3 was considered THE pre-amp to own, Frank Van Alstine took a look at it. He found the RIAA eq to be a little too off to be acceptable, the basic circuit to have a little too much non-linearity, and the power supply to be somewhat weak. He came up with solutions to all those faults (correcting the RIAA eq, reducing the distortion, and increasing the power supply's "stiffness"/lowering it's impedances), and offered a modestly-priced mod to correct the faults in the SP-3. Yet Bill Johnson continued to be considered a designer above all others by the High End community, and his ARC products therefore came attached with a certain cache' that others lacked. Some things never change ;-) .

For anyone looking for a modestly-powered tube amp, rather than pay $5995 for a poorly-designed amp that produces only 3.2 watts into 8 ohms and 1.2w into 4 (and at a very high output impedance, which will change the frequency response of almost all loudspeakers), take a look at, say ;-), the Music Reference RM-10 Mk.2. 25 watts pure Class A (a 35w Class A/B is also available, I believe), low output impedance, very long tube life, great sound, all for $5000. @twoch, if that strikes you as "B. kicking", so be it!

@tomic601, your mention of mentoring has jogged my memory (too much alliteration? ;-) . Everyone who met or even read the writings of Harvey Rosenberg knows what an interesting character he was. He was also a generous man, as I found out in the mid-80's.

Harvey was famously known for his love of three hi-fi produtcs: the original Quad ESL loudspeaker, the Futterman OTL amplifier, and the Decca cartridge. I had a Decca Blue back in '73/4, then moved on, along with everyone else, to a Supex SD-900e moving coil (into a Levinson JC-1 head amp). By the mid-80's, my interest in the Decca had been rekindled, partly because of Harvey's writings about it. He obviously understood the cartridge better than anyone else, so I wrote him (no email ;-) at NYAL, asking him every question I could think of about the Decca.

One day the phone rang, and it was Harvey. I hadn't included a phone number, but he called Glendale information and got it! He started talking about the Decca, but soon had to put me on hold to take care of something (a knock at the door, perhaps). I put down the phone, and ran for a pen and paper. When I again picked up the phone, he was yammering on, oblivious to me not being on the other end ;-) . He told me ALL about the cartridge: capacitive and resistive loading, appropriate arms, damping, etc. I wrote it all down, and still refer to my notes. Thanks Harvey, you are greatly missed.

@krelldreams, Conrad-Johnson uses the 12AU7 in their pre-amps, so I’ll guess that’s what you have. CJ products are considered to have a "warmer" sonic character than those of other companies. Some like and want that in their system, others want a different sound from their electronics.

The 12AX7 and 12AT7 are used by many other designers, both of them by Keith Herron in his well-regarded VTPH-2 phono stage. I have no doubt that unit would provide a considerable improvement over the C-J, with a more "modern" (less colored---"added" warmth is a coloration, like a filter on a camera lens, more transparent and detailed) tube sound. Roger Modjeski (@ramtubes) prefers the 6DJ8 for pre-amp use, but I don’t know that he currently offers a phono amp. Roger or clio09?

@ramtubes, oh yeah Roger, now I remember Dick Olsher's review of the RM-9 Mk.2. I found Olsher to be a reviewer from the Gordon Holt school (a school I approve of ;-), and he loved the amp. I believe his closing line was something like "Who needs an MC75 (the classic Mac amp) when we have the RM-9 Mk.2?"

I also remember The RM-5 and the Audible Illusions Modulus 2 were considered THE bargain tube pre-amps to choose between. I found the AI Mod's 30dB of line stage gain unfortunate and ill-advised, as well as it's dual-mono volume controls. The Modulus is still in production (in updated form, of course), so Roger, any thoughts of offering a contemporary RM-5 type pre?

@ramtubes, Here's a question for you Roger regarding a matter that was being discussed amongst Maggie owners on The Planar Speaker Asylum forum yesterday. One poster said of hearing from tube amps something I too hear, and that is of a sound stage that begins in front of the loudspeakers.

I heard that for the first time when Bill Johnson played an LP of Holst's The Planets (in 1973 at Audio Arts in Livermore, after he finished setting up his complete system in the shops really good room), a recording made in a large hall. The front of the orchestra was clearly located between myself and the front plane of the Magneplanar Tympani T-I's, and the rear of the orchestra was waaay back behind the speakers, sounding as if it was actually further away than was the wall behind the Maggies. I could hear the delicate triangle in the rhythm section, elevated on risers, playing in the quieter sections of the piece. It was thrilling!

Prior to that experience, at Sound Systems in Palo Alto I had heard a pair of the original Infinity Servo-Static ESL's, powered by the then-new line of SAE electronics.  Through that system I did NOT hear the image "thrown" forward of the speakers. I have subsequently heard the forward image (and great depth) from other systems (including my own), but only when the electronics are tubed.

So my question is, why is it tubes are able to do that? Is it a matter of tubes being lowest in distortion at lower-signal levels (where imaging resides?), and transistors in their curves highest?

@georgehifi, another weakness in the Cary integrated is its' very low power (much lower than spec'd) and high distortion. Modjeski made the point that in his evaluation of the amp for Stereophile, Herb Reichert may very well have been listening to only a couple of watts, where the amp is okay (in terms of distortion). If that is the case, in the Cary amp one is paying a lot more than necessary for the few "good" watts (distortion below 1%) it produces, its' relatively high price buying very little low-distortion output.

The Music Reference RM-10 Mk.2, on the other hand, produces far more power (25w Class A, 35w Class A/B), far less distortion, and far lower output impedance. And for far less $ !