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Using tube amp with electrostatic speakers.

Moons ago I started similar discussions and thought I had been given enough good advice not to approach the subject again. Here goes anyway. I've used Martin Logan electrostats for well over 30 years with quite a few different amps but have recently switched to a tube amp and dynamic speakers with which I am very satisfied.  It consists of the Cary Rocket 88R amp and Serie Reference 3 speakers. 

My brother was visiting last week and was so impressed with the sound that he decided that he might want to try a tube amp also (probably the same one as mine).  However, he is using a pair of SL3's that I gave him years ago and I'm concerned primarily about the current requirements of the Martin Logans as well as other concerns that I'm not thinking of.  I don't want him spending money on something that may not bring him improved sound so would appreciate more advice to pass on to him.  He currently uses a Rogue Audio SS amp with his SL3 speakers and, to me, it sounds very good. 
jimbreit
tomcy6's avatar
tomcy6
2,587 posts
 

ivanj, I asked about McIntosh because I have read many threads where Ralph recommends Zero autoformers for hard to drive speakers and even for not hard to drive speakers. Since McIntosh makes amps with autoformers designed specifically for a particular amp, I thought they might be a good solution for speakers with very low impedances and wanted Ralph’s or anyone else’s opinion on that match. Is it a good one or are Macs just not a good match in spite of his recommendation of autoformers? I know some people just don’t like the sound of Mac amps and point to the autoformers as the reason.

Why do you say that the curvilinear design is fundamentally flawed?

atmasphere's avatar
atmasphere
11,793 posts
 
Ralph, I’d still like to get your opinion on McIntosh amps with autoformers. Just in general, do you think they are a good sounding amp compared with other amps in their price ranges? Do they implement their autoformers well? Would they be a good choice for driving speakers with difficult impedance loads? Theoretically, of course.  We all know that good sound depends on many factors in a given system.
I was not aware that Mac was still making those; in the old days their autoformers worked quite well. But with those older amps I would not be asking them to drive anything much below 4 ohms.

The only thing difficult about the MLs is usually their impedance. Beyond that its my opinion that its a Bad Idea to make any amplifier work hard by making it drive a 'difficult load'. What happens is you get more distortion, usually of the type that make the resulting sound harsher and less detailed.

This is why I've recommended the ZERO so often in the past, as it allows the amplifier to drive an easier load.

I don't think the Macs have impedance taps below 4 ohms but usually they do employ a fair amount of negative feedback so they should work alright on ML loudspeakers if not pushed too hard.
tomcy6's avatar
tomcy6
2,587 posts
 

McIntosh has autoformers in their solid state amps and specifies that the rated power of the amp remains the same into 8, 4 or 2 ohms. 

In the MC275 tube amp they call the output transformer an output transformer but in the specs they list it under Autoformer.  In stereo mode they say it outputs 75 watts into 4, 8 or 16 ohms, and in mono parallel mode, 150 watts into 2, 4 or 8 ohms.

atmasphere's avatar
atmasphere
11,793 posts
 
If they have a 2 ohm tap I would expect them to work fine.
bdp24's avatar
bdp24
9,788 posts
 
The Music Reference RM-200 Mk.2 does itself have a 2 ohm tap. Great amp.
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