Need to learn about Audio Research

Another longtime ARC pre user here; the LS7 in my system has been its heart and soul since 1997(!). Never replaced a tube, and I turn it off only when I'm going to be gone from the house for more than a couple of days. I use a Classe CA-D200, a class D model they made a while ago (200WPC @ 8 ohms, 400 into 4 ohms). Love the combo with my ML ESLs (not Maggies, but they love power nonetheless).

@fsonicsmith

I always thought the "straight wire with gain" is one of the most meaningless cliche's among the thousands in audio. Two preamps can be "straight wires with gain" and yet sound completely different, particularly if one if solid state and one is tubed. 

This phrase was coined by Quad founder Peter Walker, who built valve and solid state amplifiers and separate pre-amplifiers, as well as electrostatic loudspeakers.

Far from a cliche, it was his design goal for power amplifiers.  On the other hand, his pre-amplifiers had multiple controls to allow the user to ameliorate playback of poor recordings, and were never "straight wires with gain".

He was incensed when a journalist suggested his valve designs sounded different from his solid state designs, and organised the best controlled comparison I have ever read about.  These is a topic here Audiogon Discussion Forum

Peter Walker (Quad) did a study comparing the sound of his own amps (Quad II and 303) tubes vs. transistors. He used RTR dubs of master tapes and presumably Quad ESL's. The two amps are well matched power-wise. It was a very thorough listening comparison using a written scoring system. He and his panelists could not distinguish between the two, until driven into clipping. It was a blind test - the amps were labeled A and B. The music chosen was various selections presumably from Decca and EMI masters. This is the most thorough test comparing tubes and SS that I am aware of! The listening panelists were recording professionals and musicians. Peter Walker's conclusion was that all well-designed amps operated below clipping will sound the same. I will point out that this was not your typical "get together in a basement with your buddies for a few hours swapping cables between two amps". It was a carefully planned and set up experiment (matched levels) - now forgotten and unaware of by today's hobbyists.

I cannot find the original paper, but three Quad models were involved (add the 405). The speakers were Yamaha, at the insistence of the journalist who later withdrew from the listening sessions - and audio journalism!  This listening panel comprised renowned British audiophiles and the tests were staged over two days.  Each blind test randomly compared two amplifier types (which could also be the same) and each panel member was asked to rate the sound quality the same, better or worse.  The results were statistically inconclusive for all panel members - nobody could reliably hear a real difference.  The amplifiers had much lower distortion than the speakers!

I've used an ARC LS 2B mkII hybrid tube pre and a D 200 SS amp in my main system for years.  Never owned any Maggies, but many other speakers have been powered by this pair, mostly dynamic drivers systems and for a while a set of Martin Logan electrostats.  Never had any issues (knock on wood...) and have loved the sound.  The LS 2B mkII is a gem, and does have a (rudimentary) remote (volume up / down and mute).  My "audiofool" :-) buddies consistently praise the this systems sound, and regularly comment on it's value.  I'd suggest this gear is worth investigating via the used market.  Happy listening! 

I've used an ARC LS 2B mkII hybrid tube pre and a D 200 SS amp in my main system for years.  Never owned any Maggies, but many other speakers have been powered by this pair, mostly dynamic drivers systems and for a while a set of Martin Logan electrostats.  Never had any issues (knock on wood...) and have loved the sound.  The LS 2B mkII is a gem, and does have a (rudimentary) remote (volume up / down and mute).  My "audiofool" :-) buddies consistently praise the this systems sound, and regularly comment on it's value.  I'd suggest this gear is worth investigating via the used market.  Happy listening! 

ARC tube amps have a definite warm “Tube house sound. And while I don’t currently have anything, I can assure you they make great products.  Having said that, the sound isn’t for everyone and or every speaker.  
Also, depending on your listening levels and whether you use sub’s, 100 watts might not be enough power for the 3.7i’s. (They really like current) but If you use an active crossover and roll the Maggie’s off @65 htz,, 100 watts is way more power than you need. There are a bunch of other variables you will need to consider also. Room size and and acoustics to name a couple.

Have you ever considered getting a hybrid amplifier?  Tubes on the input section and Mosfets for the output stage?

All the best.