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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

Showing 5 responses by muralman1

muralman1
1,527 posts
 
Technically, you guys are way over my head. I am just a consumer. It seems you techies agree on most of everything. I'm glad that class D has finally made it into this amp history exploration thread.

I do not agree Class D amp's performance value depends on digital power supplies. The best I've heard have analogue power supplies.
muralman1
1,527 posts
 
Bombaywalla,

Ar_t may have topologies of tube, and solid state down, but his "bright" characterization of D amps is off the mark. I don't know of any owners of sophisticated class D amps complaining about HF.
muralman1
1,527 posts
 
Well, Unsound, that is exactly what Ar_t is doing, "Expounding on a trait that is most damning," and it confounds me.

I am not talking about class D amps on my speakers. Sajran reviewed the amp with Gallo speakers, for gosh sakes.There are plenty of speakers, of all types, being run by class D. I also am not talking about the proliferation of module in a box amps.

If Ar_t can build an amp like Henry's, since nothing is a secret, then why doesn't he? His commercial products do not reflect the same class D amp philosophy, as Henry's.

Another thing is, I don't think a commercial entity should prop himself up as the high mucky muck of amps, holding a thumbs up, or down on his competitors, unheard. I don't see any other amp builder doing that.

Do a search on Rowland 302, or H2O, and see if the word "bright" is a common tag. I can't find any.
muralman1
1,527 posts
 
Ar_t you won't find the H2O at a dealership, nor the eAR. Being they are rare, the odds they both are in the same room with your amp, and a Rowland, sounds like the stuff of fiction. Who, and how, did this shootout come about?

Let's settle this. Send your amps to California for review. I will pay shipping both ways. What have you got to lose?

BTW, The Gallo is not a planar, neither is the Meadowlark, nor German Physics... etc. etc. Like I said, do a search.
muralman1
1,527 posts
 
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.
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