[1ZIP]

Can someone explain what exactly a "autoformer" is?  What are the advantages and disadvantages?

[James Tanner]

An auto-transformer or autoformer connects between the loudspeaker and power amplifier and allows the end user to adjust the effective loudspeaker impedance. The impedance seen by the amplifier can be multiplied by up to a factor of four, for example, turning a 4-ohm loudspeaker into a 16-ohm loudspeaker.

Unlike a conventional output transformer with primary and secondary windings, an autoformer uses only a single winding for all connections. The impedance transformation at the amplifier end is accomplished by tapping off winding sections larger than those used by the loudspeaker.

The autoformer operates right in the middle of the amp-loudspeaker interface allowing greater flexibility in fine-tuning this critical boundary between electrical and acoustical domains. One immediate benefit is control over the loudspeaker's current demand.

[1ZIP]

Thanks.

I ask because I've flirting with a McIntosh integrated for a second system.  That way I've got two different sounds to play with.  So, I went to a local Mc. dealer to audition a MA6600 (SS w/autoformers) 200 watts/Ch. ($6000). It was hooked up a  pair of Sonus Faber, don't remember the model but they were about $5000 a pair and an unknown CD source.  I had them put in a classical CD and I was astonished!  Astonished at how bad that set-up sounded.  I expected the sound to be a little warm/liquid and maybe not as transparent as my Bryston system.  I was expecting the fabled Mc. sound , what ever that is.  I couldn't believe the sound, it was boxey, muddy, no detail in the highs and no life to the sound.  I looked over at the dealer and he seemed to be happy with the sound.

Don't know why I even posted this other than the fact I was so surprised and disappointed with the sound.  I can't help but think there was something wrong somewhere in that set-up  If what i heard was the Mc, sound, I'm cured from going down that road again.  My little B-60 and Studio 20's sound better than what I heard.

Thanks for the info on the autoformers.

[James Tanner]

Hi IZIP,

I would think something was definitely wrong somewhere - the gear is too good to sound as bad you described.

The bigger question though is why the dealer or the sales guy was happy with it.  Gentlemen as I have said many times "THE DEMO IS EVERYTHING"! Whenever I go into a show demo or a reviewers home or a store I always say play me what you think sounds good.  "A demo is worth a thousand songs".  If the sales guy can not put on a decent demo then time to move on.

james

[95Dyna]

Thanks.

I ask because I've flirting with a McIntosh integrated for a second system.  That way I've got two different sounds to play with.  So, I went to a local Mc. dealer to audition a MA6600 (SS w/autoformers) 200 watts/Ch. ($6000). It was hooked up a  pair of Sonus Faber, don't remember the model but they were about $5000 a pair and an unknown CD source.  I had them put in a classical CD and I was astonished!  Astonished at how bad that set-up sounded.  I expected the sound to be a little warm/liquid and maybe not as transparent as my Bryston system.  I was expecting the fabled Mc. sound , what ever that is.  I couldn't believe the sound, it was boxey, muddy, no detail in the highs and no life to the sound.  I looked over at the dealer and he seemed to be happy with the sound.

Don't know why I even posted this other than the fact I was so surprised and disappointed with the sound.  I can't help but think there was something wrong somewhere in that set-up  If what i heard was the Mc, sound, I'm cured from going down that road again.  My little B-60 and Studio 20's sound better than what I heard.

Thanks for the info on the autoformers.

Ah, the joy of auditions and expectations!  There are some who think putting anything between the speakers and output stage of the amp is blasphemy.  Me, I don't know.  I sat in front of almost $40K worth of Mac and B&W stuff and it was very good sounding but for that kind of money it did not give me enough of what I wanted to hear to differentiate it from what I already had.  No slap on Mac's as there are too many variables in a showroom audition to draw that conclusion.  It is to me like trying on a pair of shoes that don't immediately feel just right and the salesman says, don't worry they'll feel great when you break them in.  If you've done that before you never want to do it again.

[kingdeezie]

I wouldn't be so sure there was anything wrong with the setup; but I could be wrong.

There are hundreds of products and companies that make them. There are a lot of different preferences to satisfy out there.

For instance, I bought a Channel Island Audio VDA-2/VAC-1 combo last year after everyone was talking about how great it was for the price, and compared it to DACS costing 2-3 times more. I can't wait to get rid of it, if I didn't get sucked down the TT road and spend thousands there; it would be gone already.

This doesn't mean the CIA DAC is bad; just that it doesn't suit my tastes.

There is also synergy as well. I would think that Sonus Faber with Mcintosh would be too much of the same thing, and lead to a muddy sound.

Sonus tends to be colored the same way as Mcintosh is. However, both companies make very good components.

[vegasdave]

When people say "warmth," I look at it with jaundiced eye. To me, that spells out muffled or muddy. Just my 2 cents.

[gerald porzio]

This begs the question, that aside from matching the amp to the load only @ it's nominal impedence, why is there only one mfg. who uses autoformers in the majority of it's SS pwr. amps? Antediluvian design is my answer.

[1ZIP]

It did sound better with ML's but then he lost one channel & couldn't get it back.  Then, in attempting to check the speaker terminals on the back of the unit he unplugged it and couldn't get the plug back in because of the cubby hole it was in!

To his credit he offered to let me take an open box unit home for 30 days.  But, by then I'd had enough entertainment so I went across the street and bought a Rega P 3-24.

[bmckenney]

You don't see solid state amps and autoformers very much.  It is popular with OTL tube amps to get the impedance of the speaker load to be more OTL tube friendly.  8 or 16 ohms or whatever.  I used Paul Speltz Zero's with an Atmasphere amp at one time and it worked well at making my speakers easier to drive.

I've heard that they can be used to reduce the impedence of a speaker as well, for solid state amp implementations.  Make an 8 ohm speaker look like a 4 ohm, doubling power.  I guess that can be a good thing in some implementations.  The specs on that amp say it has 2, 4 or 8 ohm output taps so maybe it is using autoformers.

If you really want to know more about autoformers, read this.

http://www.zeroimpedance.com/story.html

Bryan

[Stu Pitt]

I really like Mac and Sonus Faber together.  I've heard it a ton of times and a bunch of different combos of the brands.  I don't think its a synergy issue at all.

I'm with James here.  Something must have been amiss.  IMO it was either the source or the room, unless of course something was broken.

I'm not saying the Mac and/or Sonus Faber sound is for everyone, but I've never heard it being described that poorly.

Now that I think about it, I've heard Mac and Sonus Faber with a Sony CDP and a Music Hall CDP.  They really made the system sound bad, especially the Music Hall.  It sounded slow, dull, and just overall bad.  Maybe this is what happened?

[1ZIP]

You know, now that I think about it, I believe it was a Sony CDP.  Oh well the day wasn't a total loss I did order a P 3 and it's always fun to prowl around stereo shops.
So much gear, so little time!

[math-geek]

I listened to a McIntosh MA6900 paired with B&W 802Ds and it was so good that it has nearly changed my mind about what I previously thought of the B&W "sound".

That system was many things and slow, boxy any muddy weren't any of them.

We used to have a local Mac dealer that has since went the way of the Dodo.  He was kind enough to let me hang around and check out equipment that I had no possible way of buying.  He also sold Kef, Paradigm, Sunfire, and Marantz.  I went in there on a particularly slow day and he gave me a nice little demonstration.  The reference system consisted of a massive 400wpc Mac amp (model# ?) with a Mac preamp and CD player running Kef Reference speakers.  I didn't have much experience with high-fi at that time but it was still incredible.  Anyways he did a little switching around and put a high-end Marantz receiver in the place of the Mac preamp and amp, even my novice ears were able to tell a huge difference!  The effortless musicallity was sucked out of the system.  Until then I didn't realize what a big difference there could be in electronics.

I have not personally owned any McIntosh equipment but I wouldn't mind trying out one of their integrated amps someday myself, as I hear that they mate well with Dynaudio speakers.

[vegasdave]

Mac is good but it ain't got nothin' on Bryston, imo.

[1ZIP]

Well, I'm going to go to another Mc. dealer and hopefully the 6600 will be in a system that allows the unit to show it's abilities.  I have a lot of respect for the McIntosh line they have a well earned reputation.  I was just amazed at bad that particular setup sounded. 

 I don't ever regret buying an all Bryston system,  I would do it again in a heartbeat.   Ten years ago when I bought my first piece of Bryston gear, some audio shops tended to looked down their nose a little when hearing me speak of Bryston.  I don't get that reaction anymore, quite the opposite!