Historical look at amps

Muralman1,
i'm afraid that I'm unable to make any concrete comments on class-D amps. i've not heard one yet.

Vince......don't start again, ok?? I have too much research on this subject to be off my rocker. Remember, I have building stuff commercially for around 20 years. I am not some young upstart just getting his feet wet. We all know that Henry's amps sound just wonderful on your Apogees. Great. We are happy for you. I doubt that you have dragged a half dozen or so amps, of varying topologies, to as many different systems as we have. Trends emerge........

Well, I can not speak for C. Hansen. I do not know his motivations. I can only surmise that his inclusion of the Maxim part was to show that there really isn't any dictionary accepted definition.

As for how I know.........

At one time, they had the schematic silk-screened on the inside of the lid. I listened to it. Confirmed what needed to be confirmed. Besides, you see someone at CES or RMAF......you talk; you know someone who used to work there; you seem to have a lot of dealers in common; lots of ways that stuff gets around. None of us design in a vacuum, and secrets have a way of not staying secret. I had a dealer in Chicago once call me and 'fess up that he may have been the one who gave Mark Brasfield the idea for a transimpedance amp as an I/V stage. After he heard mine, and I 'splained how it worked. I dunno.......maybe Mark came up with the same idea on his own, just 6 moths later.

Is that both clear and evasive enough? I'm thinking of running for office! Actually, I am fixin' to head out into the hot Texas sun, and bake what little is left of my brain. If I don't return, you will know why. Just look for my dry, withered body..........

Listening to all those bright Class D amps has made me bonkers to start with. It's a joke.......you're supposed to laugh, ok. It won't kill you. Try it.

Maybe when I return tonight, I can relate a story about a buddy in the speaker business, who had a hard time deciding on the tweeter level on his new creation. Seems that he had to change it 0.25 dB depending on what brand of SS amp he listened to it on. And this was before Class D! Wonder how is faring now........I'll have to send him one and drive him over the edge! (Yeah, another attempt at humour.)

Muralman1, I have not done any serious listenig of digital amps, but, it is a characteristic that I have noticed on occassion. More importantly I think that Ar_t is suggesting that many if not most digital amps seem to take measures that allieveate this phenomonon. As Ar_t has made clear, he currently manufactures digital amps. I seriously doubt he would make and then advertise a product as having a trait that is the most damning in the business. Furthermore he has opined that this particular tratit in this particular technology seems to be more system dependent than usual. I don't have the experience as to whether digital amps have become the new standard bearer presently or if they will in the future. I am hopefull that they will. At the very least they show great promise.

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.

Hey Ar_t,
I cut & paste an exerpt from your earlier post:-

"The crux: "current-feedback" amps have a bandwidth that remains constant, regardless of gain. Traditional feedback amps do not: as the gain increases, their bandwidth goes down."

This does *not* read correct to me! AFAIK, the gain-bandwidth product of a voltage-mode amp is fixed for a certain topology implemented by the designer & with a fixed set of devices. What I have seen tho is that as one increases the gain, the dominant pole frequency goes down & when the gain decreases, the dominant pole frequency increases. (you've got to have compensation somewhere in there to counter-act the phase shift of the music signal as it propagates thru the amp). However, the unity gain frequency, often used as the bandwidth of the amp, remains fixed. The unity gain freq can be increased by reducing the in-circuit parasitic poles (better devices), cascoding & by increasing the bias current.
Maybe I understood incorrectly. Perhaps you can clarify?

BTW, there is a company called Comlinear that makes current-mode opamps & other electronics. I don't think that it's audio grade stuff (but then it might be!) A lot of their circuits are based on the current conveyor (CC II) concept. I've never used them personally but their architectures sure look different than traditional voltage-mode amps. They also seem to be perhaps the lone star player in that field.