Historical look at amps


The amplifier evolution thread reminded me of the history of amplifier circuits that has occured over the last 20 years. Lots of changes but the one that stuck in my mind was the change in feedback circuits. In the early 1980s a good amp like Crown, McIntosh, Phase Linear etc all had large amounts of feedback and distortion levels of 0.00001% IM and THD. These amps sounded bad and the question was raised (and still is) why objective measurement didn't jib with listening tests. A Finnish engineer (OTTELA) came up with a new measurement called Transient IM Distortion (TIM). I wont go into the details but it did show that large amounts of feedback which made static IM and THD measurements good, made music waveforms bad. The result has been today's amps with low levels of global and local feedback, and better sound but with IM distortion levels of only 0.01% (and of course tube amps with more even then odd distortion harmonics). Just recently Ayre, and probably other companys are offering zero feedback designs. Feedback circuits have been with us since the 1920s and we are now just elliminating this basic design feature in modern amps and preamps.
keis
agree, Herman, time to exit this thread.

Ar_t has been very helpful in revealing the dark secrets of amp design. I don't know if this "So why do you feel threatened when I tell the dark secrets of the world of amp design." was directed at me of Muralman1? IFFF it was directed at me, I'll say that I am not threatened in the very least. Au contraire, I stand to gain a lot more knowing the info shared in the thread. Your having 20 years of product design doesn't diminish my capabilities one bit. In fact, we can talk at the same level, which might be enjoyable.

Anyway, what should have been learnt from this thread is that manuf will do the bare minimum to disclose aspects of their design. Even good/very good manuf held in high(er) esteem by consumers. There is no standards committee in this audio consumer market that'll keep them honest. The only people who can do this is, us, the consumer. This will happen ONLY if we consumers are educated enough to ask them pointed questions that'll give us an idea of what the manuf might have done inside the product we are about to spend a ton of cash on. Like Ar_t said, if someone is putting down $3K on audio gear, expect some serious questions to be asked! Not unreasonable.
Also, don't simply eat hook, line & sinker what the manuf has to say about his product. Ask some serious questions. Try to understand their implementation.
By keeping manuf-consumer loop closed, both parties will benefit - we will supply feedback about their products, keep them honest & let them know where their performance is sub-par. Hopefully this will not fall on deaf ears & they'll make products that we are seeking using the best possible methods to implement them. You want audio to be around, we'd better help each other. No other way out. (you do this at your place of work with your suppliers, correct? why is audio any different?)
I did not say that I heard them at a dealer.

I sent them to guys who had aleady brought one of those models in to audition. And sent them back, unsatisfied. There are a few times when I found someone who actually owned one of those brands. There is a big difference when doing a serious side-by-side comparison, as opposed to a "shootout", where there has to be a winner and a loser.

Actually, you may recall, I didn't buy their explanation why they preferred ours over the others. Some guys get carried away exaggerating minor warts. The guys that I placed the most faith in their reasoning was the ones that said they all sounded very close, but chose ours for other reasons. Features........ease of use and interfacing.......looks, whatever. As grateful as I am when someone thinks ours sounds better, I tend to dismiss their enthusiasm when it overflows with superlatives.

I know the Gallo isn't planar. Strangest looking thing I have ever seen.

No, I am not doing a Google search, because I know the truth. I have to.......I build this stuff.

Honestly, I do not see why you seem so defensive. I have not maligned Henry's, or anyone else's, efforts on this genre of amps. I may have a different opinion wrt their pros and cons. They may be among the best we have to work with at present, but I seriously expect that we will have many other options in the near future. And you can rest assured that I will be just as honest and forthcoming about them, at that time.
Guys,
Oh no! You all have got Muralman started again!
To Muralman the H20's are the perfect amp, and can do no wrong...let him continue to live in his fantasy world.
Let's not jump all over Muralman without the consideration of his rather unique situation. How many of us are driving one of the most difficult loads (Apogee Scintilla 1 ohm) in all of home audio? Very very few I'll bet. I had Apogee Calipers and although they are easier to drive than Scintillas they are still a bitch. OTOH I am not endorsing the H2O as I've never heard it but I suspect there are only a limited number of amplifiers that will drive the Scintillas properly. He found one. So what? Let him have some fun.
Audio Girl, we all live inside our heads, don't you know? There isn't a thing you feel, touch, hear, that isn't a product of your brain activity. :)

Ar_t has said, repeatedly, tucked into his long winded lectures, ICE highs are wrong. I say, the ICE module is a chameleon. Actually, I'm borrowing that from another thrilled H2O owner. It can be made to sound like just about anything the designer wants.

Henry's amp has a full kilowatt high quality transformer, and over 70,000 mƒ of capacitance. These figures far exceed that of competing amps. There are other devices that I'll wager is unique in class D amp design.

Whether that is bad or good, one can debate. One thing is for sure, Henry builds amps his own way. No one should assume what they sound like.