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Old 31st December 2012, 05:36 PM   #7921
dvv is offline dvv  Serbia
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You know, Brad, the audio business reminds me more and more of the art business. Nothing objective, all subjective.

That reminds me of a scandal in London in the ate 60ies or very early 70ies. A few journalists got a monkey to paint a painting or two. They then exhibited it in one of London's prime art galleries. And roared with laughter as they read the critic reviews - promising young artist, understand colours like no-one lese around, and so forth.

A few days later, they photographed the budding young artist and printed his portrait. A scandal exploded, and several resignations were called for, a few of which were elicited from very notable names of the art world of the day.
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Old 31st December 2012, 05:41 PM   #7922
bcarso is offline bcarso  United States
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Originally Posted by a.wayne View Post
So are wall warts still available and recommended ...?
There's probably a black market in them (simple plug-in transformers) in California But they have taken them off of shelves at retailers I believe. I saw some transformers yesterday at Fry's, but they turned out to be ones with no cases, good old-fashioned ones. I didn't look inside the boxes to see if they were dual-bobbin or not.

Perhaps you can still get them as replacement parts via mail order.

Now one could contrive to make a supply that achieved the low standby current required by the California Energy Commission that still had low mains-to-output capacitance. But it would be hard-pressed to meet the operating efficiency standards.

I believe, when you put your power supply together in your enclosure(s), and if it is a "hifi" product, you can request an exemption to the efficiency standards.

But this is all for your own good, don't you see? [sarcasm]
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Old 31st December 2012, 05:41 PM   #7923
a.wayne is offline a.wayne  United States
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Yep , no difference ....,
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Old 31st December 2012, 06:47 PM   #7924
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Enid May Lumley

Birth: Jan. 23, 1938
Ellsworth, Hancock County
Maine, USA

Death: Jul. 15, 2008
Yuma, Yuma County
Arizona, USA

Enid May Lumley (1938 - 2008) - Find A Grave Memorial

Enid used to write "Lumley's Corner" for The Absolute Sound" Magazine, and also wrote for the International Audio Review. (aka Auntie Enid Lumley)

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Yuma Regional Medical Center is where she discovered she had advanced lung cancer in March of 2008. Enid passed away at La Mesa Healthcare Center, Tuesday, July 15, 2008.
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Old 31st December 2012, 07:40 PM   #7925
bcarso is offline bcarso  United States
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Originally Posted by Speedskater View Post
Enid May Lumley

Birth: Jan. 23, 1938
Ellsworth, Hancock County
Maine, USA

Death: Jul. 15, 2008
Yuma, Yuma County
Arizona, USA

Enid May Lumley (1938 - 2008) - Find A Grave Memorial

Enid used to write "Lumley's Corner" for The Absolute Sound" Magazine, and also wrote for the International Audio Review. (aka Auntie Enid Lumley)

**********

Yuma Regional Medical Center is where she discovered she had advanced lung cancer in March of 2008. Enid passed away at La Mesa Healthcare Center, Tuesday, July 15, 2008.
And by all accounts I've heard, a very nice woman.
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Old 1st January 2013, 12:48 AM   #7926
a.wayne is offline a.wayne  United States
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Wow sorry to see such ........
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Old 1st January 2013, 01:35 AM   #7927
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I loved Enid. Great ears, nice bod!

Last edited by john curl; 1st January 2013 at 01:55 AM.
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Old 2nd January 2013, 05:39 PM   #7928
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how about a little change of direction since the thread is somewhat stalling?

have you heard about the Devialet D-Premiere?
well it's a class-D amp at first look but the makers insist it's "something different".
it's just been reviewed at Stereophile on 12/28/02: Devialet D-Premier D/A integrated amplifier | Stereophile.com

by Mr. Atkinson himself, who has nothing but praise for its sound. AND its measurements are exceptional: Devialet D-Premier D/A integrated amplifier Measurements | Stereophile.com

here's a more in-depth description (well, not exactly advanced EE, coming from 6moons, but anyhow): 6moons audio reviews: Devialet D-Premier

since maybe you're not exactly interested in all the literature that comes with any 6moons review, I'll help you skip to the interesting part:
Enter Pierre-Emmanuel and Mathias. They discovered a way to match both types of amplifiers by using not one class D amplifier for each class A channel but four. Each of these runs at a 90° phase difference to the next even though receiving the same input signal. With four phase-rotated co-amplifiers, the class A amp only sees 1/4th of the switching load. An additional advantage is the output resistance of the class D amps being reduced by 75%. Both sets of amplifiers connect in parallel to each channel’s speaker terminals.

so, we have a high-voltage, low current class-A amp that runs in parallel with 4 phase-shifted class-D amps. I'm trying to get my head around the concept and understand if this is more than marketing blurb. let's try and not jump to conclusions and just label it a nice, expensive box with a halo of clever marketing surrounding it.

what's certain is that the high-frequency carrier is completely absent in the Stereophile measurements which tells us something may actually be different to be worth some discussion.

what do you think?
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Old 2nd January 2013, 06:23 PM   #7929
bcarso is offline bcarso  United States
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Quote:
Originally Posted by mr_push_pull View Post
how about a little change of direction since the thread is somewhat stalling?

have you heard about the Devialet D-Premiere?
well it's a class-D amp at first look but the makers insist it's "something different".
it's just been reviewed at Stereophile on 12/28/02: Devialet D-Premier D/A integrated amplifier | Stereophile.com

by Mr. Atkinson himself, who has nothing but praise for its sound. AND its measurements are exceptional: Devialet D-Premier D/A integrated amplifier Measurements | Stereophile.com

here's a more in-depth description (well, not exactly advanced EE, coming from 6moons, but anyhow): 6moons audio reviews: Devialet D-Premier

since maybe you're not exactly interested in all the literature that comes with any 6moons review, I'll help you skip to the interesting part:
Enter Pierre-Emmanuel and Mathias. They discovered a way to match both types of amplifiers by using not one class D amplifier for each class A channel but four. Each of these runs at a 90° phase difference to the next even though receiving the same input signal. With four phase-rotated co-amplifiers, the class A amp only sees 1/4th of the switching load. An additional advantage is the output resistance of the class D amps being reduced by 75%. Both sets of amplifiers connect in parallel to each channel’s speaker terminals.

so, we have a high-voltage, low current class-A amp that runs in parallel with 4 phase-shifted class-D amps. I'm trying to get my head around the concept and understand if this is more than marketing blurb. let's try and not jump to conclusions and just label it a nice, expensive box with a halo of clever marketing surrounding it.

what's certain is that the high-frequency carrier is completely absent in the Stereophile measurements which tells us something may actually be different to be worth some discussion.

what do you think?
I commented earlier somewhere in diyaudio that I was puzzled by the high noise, which dominates the HD measurements shown in JA's sidebar. And this is at the 0 dB gain setting iirc. When Atkinson turned the gain to maximum the noise was atrocious, but even he admits that this is an often-unrealistic condition.

I am looking forward to the followup in which the performance of the phono input will be discussed.

The concept of using class A amps "inside", or alongside, of class D is not new. There's prior art and I believe at least several patents. Perhaps the quadrature arrangement of the switchmode amps described is novel. But in that connection, be mindful of Gerald Stanley's patented interleaved approaches, which as directly-switchmode designs, increase the equivalent switching frequency while drastically reducing output ultrasonic noise.

I'm open-minded, but I can assure that, from personal experience and study, it is very difficult to do something truly new in switchmode and hybrid amps. It is a minefield of IP and patents.
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Old 2nd January 2013, 06:35 PM   #7930
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Quote:
Originally Posted by bcarso View Post
I'm open-minded, but I can assure that, from personal experience and study, it is very difficult to do something truly new in switchmode and hybrid amps. It is a minefield of IP and patents.
I didn't mean it that way, I'm highly skeptical when "revolutionary" inventions are mentioned, especially in the context of audio. actually, the mere mention of the word "technology" (followed by an acronym) in a review makes me rise an eyebrow. I mean, damn it, this is what marketing guys in corporations do, they invent/change names hoping that everyone will buy into thinking there's really something going on there LOL

I'd be interested in learning more about this, I've searched for the mentioned patent, thanks.

(this still leaves the question: why is the HF noise of the "conventional" D-amps to be dreaded? I haven't found any credible explanation yet)
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