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
Only problem with the first 2 suggestions........

I know of some people (on other forums) that make countless useless posts, only so that they can get their name in front of as many people as possible. Again.

I would rather not appear to be one of them.

Not many people are familiar with my company. We keep a low profile.

I think the best approach would be some sort of indicator for commercial posters. Maybe someone who knows the powers that be can suggest that. I do not want to e source ofd confusion, any more than you guys need any.
Ar_t,
I see that you are being extremely difficult on a simple matter like this!
I note an extreme resistance on your part to openly cite your affiliation w/ your company thinking that somehow by revealing it we are going to jump on you.
For such a simple matter as this you are making excuses.
Whether you are low profile or not is of no concern to me. What I/we want to know from your posts is that you are an audio industry person & weight your comments accordingly.
And, I see that you are trying to avoid this at all costs.
Something does not seem correct to me! No wonder AudioAsylum designates their dealer sub-forum as "Shady Lane"!

Forget about the other people who "I know of some people (on other forums) that make countless useless posts, only so that they can get their name in front of as many people as possible. Again."

You post sensibly + make very clear your association with the audio industry & you will *not* end up looking those other people & neither will you create any confusion for us. You haven't been long enough on these Audiogon forums - we can handle quite a bit of confusion before we cry "uncle"!

You are *not* coming across clean, Ar_t - something is not right here!
I would have never thought of the Mc amps from the 80's as bad sounding though..
Jsujo, On Mac amps, he means in his opinion to his ears. Millions of people think otherwise and have voted with pocketbooks. At the end of the day it ONLY matters what sounds good to THAT person.
I am not being difficult. I have a long-standing feud with someone that does exactly what I am commenting on. It will just be a matter of time that he finds this through Google, and the feud will spill over to here. So, while it may be beneficial to you, it may give him fodder to slander me even further by using my posts here as ammo.

Trust me.......ok.

Ok.......my company is Analog Research-Technology. We used to have an entire line of electronics, way back when. Way back when we had dealers. The migration to HT put them all out of business, so we went even more underground than usual.

With the recent introduction of the new "self-oscillating" Class D amps (digital amps to some of you............), I decided to gear up and start making 5-channel amps for the HT crowd. Somehow, I have a hard time getting excited about that market, and since we were amazed at how good they sounded, we became sidetracked and made some stereo versions.

One of my customers mentioned here that he has one of amps......well, actually, he has a 5-channel one also......and next thing that you know, my phone is ringing, wanting info, etc. If it were not for that, you never would have heard of me.

Is that help any???

Or do you want:

I live in Texas. I eat really hot peppers and curry. I have a '73 'Cuda hidden away in the garage. I don't drive it much because gas costs too damn much, it rides hard as hell, and I am too damn old to get excited about trying to operate a 4-speed with a clutch that is even stiffer than the suspension.

Or.......

I don't like the sound of feedback. I guess that you have already figured that out. I tend to build stuff that is full of discrete circuitry. Trying to find ways to add all that extra stuff onto a Class D amp module was a minor challenge. The next ones will have even more discrete circuitry. (Hint: it is either power supply, or input stages.)

Anything else that you may care to ask?