How good is the McIntosh MC-2300 vs modern SS amplifiers?

John Curl gave a most informative talk on the Wall Of Sound used by the Gratefful Dead. He had a lot to do with the speaker end of things but had not much to say about the amplifiers which left me curious about them. 

I pulled up the following manual and schematic and suggest anyone interested in advanced circuit design of the 1970s have a look ..

Read this

and this

There is an earlier discussion about autotransformers where some call the autoformer a "band aid" for a poor design and others slurs. However this is a fine amplifier, virtually bullet proof, and used in great numbers by a band known for its incredible sound. 

I welcome any comments and questions. 
How about an OTL that can drive a wide variety of speakers properly?

No such thing, unless you stick an autoformer band-aid on it for the hard to drive ones. Then you ruined the whole advantage of the OTL design and what it can do.
Your better off getting one of your amps to do the job if you wish to stick with tubes, or putting a proper output transformer on the OTL, again a backward step to what an unhindered OTL is capable of giving with the right speaker.
Here is an interesting story that happend to me. Jim Jordan, the designer of Vaughn speakers fell in love with the Wavelength 300B Cardinal with silver transformers and all. Big bucks for a 7 watt amplifier. This amplifier has rather low damping, but within its power range I assume it to be a good amplifier. He named his speaker after the amplifier. In this case the amplifier came first and he designed a speaker he felt worthy of it as other speakers he tried were not.

Then he met me, actually I went to his house to hear his speakers. I took along a rough prototype of my OTL for him to hear. Somehow he convinced me to make one for him and one for his customer in stereo on a nice chassis. Now he uses my AUTOFORMER OTL all the time. It has very low distortion very low output impedance. It is of the Futterman School which always has low output impedance. Mine only two output tubes, triode connected, and one driver tube per channel. Most OTLs have 6-12 output tubes per channel. Lots of heat, lots of matching.

The autoformer has no special materials, I make them of standard copper magnet wire and M6 Iron. It is very small, costing a fraction of a silver 300B transformer. It is partially in the feedback loop or not, as desired. Id does effect the sound and Jim moves it from time to time for different listening. He likes the subtle changes it makes.

I wound 4, 8, 16 ohm taps and 32 ohms is direct output. At 32 ohms the amplifier puts out 30 watts into a 32 ohm load. An 8 ohm load connected to the 32 ohm tap produces 3 watts because the tubes can only provide that much current (about 1 amp). But any load connected to its proper tap will put out 30 watts. To my suprise the Autoformer extends the high frequency frsponse from 120 KHZ direct to 160 Khz using the 8 ohm autoformer tap into an 8 ohm load, or 4 into 4, etc. All the taps produce the same results into their specified load.

I arrange a feedback wire on a lug and tell the user to move the feedback wire to whichever tap they are using so the feedback is always on the tap looking right at the speaker. Sometimes the put it on a different tap and like that better. Its all good, the amp is stable and happy.

In closing the SA-6 I deisgned for Counterpoint and the large Futtermans will drive a wide variety of speakers with 100 watts per channel with very low distortion and high damping. Keep in mind that the Circlotron amplifiers are an entierly different animal. They do not have low output impedance of a lot of current. All OTLs are not the same

I invite George and others to take a little time and learn about the Futterman style amplifiers and then say something. Little by little I will get around to all of it, but it took me years to fully appreciate his work, the man was very smart and I am happy I got to spend an afternoon in his shop. 

So what your saying is an amp that can drive the Wilson Alexia’s known impedance of down to 0.9ohm is a bad amp?????

No you’ve got that arse about face, the speaker is the problem being too hard to drive and the amp that can do it is a great amp, and will not only drive it but anything else as well. Definitely not a bad amplifier waiting to find a home.

Cheers George
I hope I didn't imply that. An amplifier that drive 0.9 ohms would be a very good amp if all other things were up to snuff. There are lots of both good an bad ways to drive an ohm.

Speakers are the designer's sonic goal, his taste, his dream. In many cases he doesn't care how he gets there. Some care and some do not care about the difficulty of their load, not their problem. I would suspect most people who are serious about speaker design have good rather universal amps with high damping, lots of current and voltage. Why wouldn't they? Therefore if you buy their dream you had better ask its characteristics or how they drove it. 

On the other hand if someone is interested in 300B amps, like Jim Jordan, the speaker choices are limited and one is playing in an entirely different field which is not universal but has limitiations. Here the speaker/amplifier interactions are going to be important, obvious and likely hit you in the face like the Circulatron that produced a 8 db peak at 50 Hz and a marked loss of highs in my QUAD 63. The 8 dB peak surprised me so much I got a oscillator and meter and measured an 8dB rise at the speaker terminals at 50 Hz and many dB fall off about 400 Hz. The 63 was not longer Mr. Walker's 63.

In the  HI FI world some people design speakers that are hard to drive, yet there are many amps capable of driving them. At a wide range of prices. So what is all the fuss about? 

However what do we do with amplifiers that have high output impedance and limited current? People buy lots of them.

May I remind all that the topic of this thread is about what an autotransformer can do for matching the load to the amp. Whether or not a Gryphon sounds better than the old Mac is not the issue and certainly not the money which few can afford. I also find it odd that Gryphon is not in Stereophile Rec Components, nor could I find a review or any mesurements. If someone has a link I would love to see this amp's performance. Perhaps is all just a pretty face.
The Mc 2300 was horrible ,the pots Mac used get dirty easily & begin to scratch when gain levels are changed and I'm not the 1st to experience that problem ,I'm a huge McIntosh fan/collector but the Mc-2300 performs as good as it dosent look ,I've got mig welders that look nicer .