MAC Autoformers?

ramtubes
An Autoformer or any transformer cannot fix a difficult load and only affects stability in a poorly designed, on the edge amplifier.

What I’ve been saying all along, they are a band-aid fix for amplifiers that are "not capable" of doing the job properly without them.

They are also "not able" to make an amp that "is very capable" without them sound better. If anything they make them sound worse.

Cheers George

I can't be certain but I have owned my Lightspeed for around 9 or 10 years.

Wow I think your right, the MkII, was released around 2006 when all MkI's were recalled and converted.
I think it's time for a MkIII, what do you think Anthony? Upset the active preamp brigade some more?

Cheers George 

ramtubes
I also would like to note that the OP of this thread, Paul R owned a RM-9 Special Edition. We miss Paul, a really good guy.

Totally, "top bloke" had many late night discussions with him.
He really loved his RM-9 Special Edition which he said was a perfect match with my "Lightspeed Attenuator" which he also started thread on, which exploded to over 18 million hits, made my life hell and interesting at the same time, rip Paul miss you heaps.

Cheers George

ramtubes
Ralph,
I did read your white paper before entering this discussion. Lets just agree to disagree. Peter Walker designed the 57 to be used with an amplifier with a damping of 20 and even specified the series inductance. To say that these speakers will play with a damping factor of 1 is not fair to the speaker, no matter that some people like a widely altered frequency response. How can we discuss little differences in distortion when the frequency response has been so altered to make the speaker unreconizable?

Hear hear, good to see someone else thinks the same, about amps becoming tone controls with wild speaker impedance curves. Low output impedance (damping factor) and current are the only fix to make the amp stay reasonably flat.
Or I suppose you could have an "inverse tone control" to counter it, but the amp in question will start to gag itself very early in volume level.

Cheers George

was quite pleasantly surprised to see the amp double down from it’s 8 Ohm tap down to 4 Ohms

If you don’t change the tap, it doesn’t double at all when the load impedance halves from 8 to 4ohms
And you can’t change the trany tap from 8 to 4 half way through a musical note, when it decides to dip from 8ohm to 4ohms then back up again.
Autoformers good interim fix for amp/speakers if the amp can’t drive the speaker without it, till you get the right amp 

Cheers George

08-03-2018 3:21pmWith easily driven speakers ( impedance ), I much prefer the Mac amps without the autoformers. Same with OTL tube amps.

https://i.pinimg.com/736x/56/c1/a3/56c1a3c6bb97f86a61c4144444b20508--emoji-faces-cartoon-faces.jpg

But, let us be real. Many fine speakers are not easy to drive, and autoformers are there to keep the amplifier safe and sound ( pun intended ) and better match the speaker. Enjoy ! MrD.

These speakers then should have different amps that can handle their loads.

Cheers George

You shouldn't question what they do, they have their job moderating and are good at it.
Like I said I doubt very much the post was deleted because of a reference to another audio website, it was probably whatever else was said, in the way it was said. 

Well, my last post was removed because I mentioned another audio website.

I doubt that very much, I post links to Stereophiles bench measured results all the time, it must have been something else or the tone of your voice.

Be careful moderators

One should never threaten moderators, even in passing comments.

bifwynne
I am confused. I get using autoformers on high output impedance tube amps. The autoformes will make the amp think it is driving a higher impedance speaker load and thereby improve the damping factor, make the load easier for the tube amp to drive and may smooth out the FR of the speaker.

But why would one use an autoformer on a high quality, stable, hog wattage SS amp. These beasts were (should be designed) to handle demanding speaker loads. I surmise that most speakers on the market today were voiced to be driven by a high current capable voltage paradigm SS amps.

It’s simple! It’s two things, a gimmick, or a band-aid for gutless amps that can’t drive those loads.

It’s not a patented idea, all you you have to do is to look at how many other "well known" well designed solid state hiend amp maker use output transformers? A BIG ZERO, if they did it was as a gimmick or an aid for that amp to drive speakers they normally couldn’t.

Why do good OTL’s tubes not use them on speakers they’re comfortable with?? BECAUSE THEY SOUND BETTER WITHOUT THEM (Ralph), so long as the speaker load is ok for them. The moment the load get’s too difficult for them with other speakers then they’re better using an autoformer, I would change the amp instead.


Cheers George

So here is the question: a speaker with huge variation in impedance curve will receive considerably more power where the impedance deeps way below its average curve

If the amp can’t supply like this it won’t sound flat from 20hz to 20khz, look at the (grey trace), this is the frequency response of the amp into a mild simulated speaker load, and it will benefit from the use of an autoformer..
https://www.stereo.net.au/forums/applications/core/interface/imageproxy/imageproxy.php?img=https://w...

An amp that can supply, looks like this (grey trace) nice and flat 20hz to 20khz and if you put a autoformer on it, the sound will be worse.
https://www.stereo.net.au/forums/applications/core/interface/imageproxy/imageproxy.php?img=https://w...

Cheers George

It seems you are consistently more interested in the technical data on hifi equipment that I'll bet determines what system or systems you own and like.  

Do you ever throw care to the wind and just trust your ears?

I alwasy do both Pops. As do all designer of good amps, without bench testing, laws of electronics, tech data, if you bought such an amp off some who doesn't do these you'd have a pile of junk. 

Cheers George

If I did that, the test would be compromised by the fact that the amp used in the test was not designed to be used with autoformers.

Wrong, your grasping for straws!

The autoformer is just as suited to a good amp compared to one that is compromised.

And if your happy with it that’s fine.

BTW shoulda kept the  Pass Labs X250.5

Cheers George

Roxy?
What I'm saying is simple, if an autoformer sounds better with a ss amp into a speaker that amp wasn't a good match for that speaker to start with.
I noticed your avatar and it looks to be one of those amps that would benefit from an autotransformer into speakers it normally shouldn't be mated with. So your happy if it does.
 
You can prove this to your self, there are a number of Zero for sale used some as low as $250 for the pair, put them on a known "good" Solid State amp  that can drive most speakers, and you will put them back up for sale quick as a flash.

Cheers George 

unsound
I’ll hazard a guess that Mac chose to use autoformers way back when early transistors weren’t as reliable. They chose to use the autoformers to increase reliability (which way back was part of Mac’s separation from much of the competition) and because it fit in with design parameters that they were already comfortable with. Most speakers of that era were thought to be used with tubes by the end user, that might not have realized the compromises that the autoformers introduced. IMHO, there is no good reason to use autoformers with the rugged transistors that have been available for almost 5 decades since then.

Yes this is well pointed out by unsound, they continued today because of a market niche they made for themselves back then with the "new questionable semiconductors" of the time. They continued with it even though it’s not with today’s semiconductors, and has become the opposite, a compromise rather than an aid.
Or roxy54, a band-aid fix for poorly designed amps that can’t drive certain speakers. In this case your better off with the right amp.

Cheers George

Saying that autoformers are a fix for a flawed amplifier design as Stanwal said is in my view just ignorant.

I don’t think Stanwal meant that, they didn’t purposely go out and design a flawed amp.

I believe he meant that with an autoformer an amp can be designed with lax’ed parameters eg: that make it stable. And that an autoformer can then isolate it from the bad outside world speaker emf etc, that may make it go into oscillation or ring or whatever. This this autoformer makes this amp listenable and reliable. It's a Band-aid.

But if the amp had great design in the first place as not to have any lax’ed performance issues, the an autoformer is definitely a backwards step regarding sound quality.

Cheers George

roxy54
Did you perform this test?

Yes I had a customer trade a pair in, he tried them on his Lamm 1.1’s and didn’t like them, I put them on my very good solid state amps with my ML ESL speakers to see what they did, and it made them sound like old an Williamson tube amp soft polite and rounded. As I said the same years ago in Audiogon.

Mac did build good amps, they were the 275's, should never have gone to ss with transformers. 

Cheers George

my guess is of course not......geez.....

Really!!!

That is the first time I’ve heard a claim that the autoformer was a hindrance to better performance;

Why hinder the performance of a well designed solid state amp with an autoformer, unless it was a bad designed one to start with.
A simple test is to put a well known Auto Former that’s used on OLT’s to make them "sort of work" into speakers they can't drive without them, on the rear end of good solid state amp (say a Pass Labs) and watch it transform into rubbish.

Autoformers are "band-aid fixes" for amps that are not right before them to be able to drive into loads they shouldn’t be on without them. Get the right amp to start with, don’t just put a band-aid on.

stanwal
For us non Mac enthusiasts the autoformer has always been proof positive that Mac had no idea how to design a transistor amp, perhaps they are coming to their senses at last.

+1

nsgarch

I agree with Stan. I just wrote this a few minutes ago:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1262654269&read&3&zzlNolitan&& Report this

+1

Cheers George