LEF (Load Effect Free) Amplifier technology

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#3
G.Kleinschmidt said:


It starts with a bunch of complete misrepresentations and outright BS on the limitations of nfb end then goes on to imply that the transistors in their amplifier miraculously work with constant Vce and Ic. Far out!
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C'mon...
When I use a voltage follower I often load the device on a counter-modulated CCS and power it from one more follower. Probably guys use similar approach inventing a new fancy name for the same old good bicycle.
 
#5
Lumba Ogir said:
Wavebourn,
I bet they are using your Tango topology.😀
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So what?
It's public domain... Tango is a combination of MOSFET and degraded BJT.
"Privileged conditions" for cathode followers were used long-long time ago by Tektronix in their oscilloscopes (one more follower on top) and by White in his cathode follower, though a CCS modulation was made by White from output (feedback by current).
I modulate both CCS and "top" follower by input signal (feed-forward approach) for better phase alignment, it is the difference. Also, "Tango" is the way to get higher current variations with less distortions than using one device, either BJT or MOSFET.
 
#7
Lumba Ogir said:
Wavebourn,
that`s one of your eccentric ideas.
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To put in public domain?
Sun Microsystems did that with SPARC technology.

Maybe you would need better drivers for the Festival speakers?
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Why?
That drivers are fine. Designed for police motorcycles they are very effective, and when boxes are properly damped and amps equalized they sound gorgeous. Guests and singers on the recent home concert were impressed.
 
#9
G.Kleinschmidt said:
I'm sorry to say it, but that LEF amplifier white paper ( http://www.aqvox.de/LEF_Amp_en.pdf ) is stupid beyond belief.

It starts with a bunch of complete misrepresentations and outright BS on the limitations of nfb end then goes on to imply that the transistors in their amplifier miraculously work with constant Vce and Ic. Far out!

Cheers,
Glen
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Yes, the language is very flowery. The references to Leonardo DaVinci are pure marketing BS.

Technically, it sounds very much like the Halcro output stage and others. They seem to be describing localised output stage feedback with a floating psu. Good ideas, in fairness, but not novel.

They make claims, summarized in the box at the end, that are somewhere between highly misleading and downright dishonest:
1) no feedback loop
2) extremely low load effect
3) extremely reduced Vce range
4) extremely reduced Ic range
5) split handling of voltage and current output

If you are an Engineer, your nature abhors misleading claims. If you are trying to sell hifi for a living your livelihood may depend upon it.
 
#12
I have heard the Aqvox phono preamp, but I'm a little confused on how this applies to a phono preamp, since its talking about speaker load. Anyway, the Phono preamp is pretty impressive for its price. Stereophile really liked it, and I was interested in DIYing a balanced phono pre, I live near Elusive Disc, so I decided to give it a shot (Take a listen). It really is about the quietest phono preamp I have ever used or heard. I'm still considering doing it myself, but am debating if I want to bother. I have so many projects "in the works" that I haven't finished, and for the price, I'm not sure I can save a whole ton. I have the opamps I would use, and a regulated power supply I built for something else I could use, but beyond that, no PCB's, no resistors, and not enough capacitors. By the time you price in a chassis, transformer, connectors, pcb's, etc, I bet I will be up over 500 dollars. While that isn't anywhere near 1500, the aqvox does use discrete stages instead of opamps, has some engineering behind it, and who knows if my first prototype would actually work out, if not, then there is the money I wasted on that, and the money I would have to spend on attempt number 2, 3, 4, etc. Anyway, my point is, I really like the Aqvox phono preamp and thought it was a pretty good deal. I am also interested in the Aqvox Class A amp when it comes out, assuming we get one here in the states. I probably wouldn't buy one, but I would be interested in hearing it.
 
#13
Thanks for the impressions pjpoes - sometimes (and only rarely) there is some engineering quality behind the BS marketing hype. I haven't heard the preamp but was impressed by the range of functionality & features that they incorporated into it.

Has anyone heard a power amp using LEF - I think CEC are the only power amps using it?
 
#14
#15
Can an anti speaker(!!!) circuit, one that maintain the speaker to remain resistive at the lowest value be designed and connected across the speaker, so that the amp sees a fixed resistive load.

Looks like I had lack of sleep...

Gajanan Phadte
 
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