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Old 30th July 2008, 03:11 AM   #1
jkeny is offline jkeny  Ireland
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Default LEF (Load Effect Free) Amplifier technology

What are your thoughts on this concept & execution? Any ideas on the circuit details?

Has anybody heard the AQVOX phono amp or CEC AMP 71, both of which use this technology? The AQVOX gets some great reviews but i haven't seen any review on the CEC amp.

Info on LEF here: http://www.aqvox.de/tech.html and here:http://www.aqvox.de/tech_ci.html
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Old 30th July 2008, 05:41 AM   #2
GK is offline GK  Australia
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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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Old 30th July 2008, 09:39 AM   #3
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Quote:
Originally posted by G.Kleinschmidt


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!

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.
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Old 31st July 2008, 09:59 PM   #4
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Wavebourn,
I bet they are using your Tango topology.
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Old 1st August 2008, 01:52 AM   #5
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Quote:
Originally posted by Lumba Ogir
Wavebourn,
I bet they are using your Tango topology.
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.
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Old 1st August 2008, 02:28 AM   #6
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Wavebourn,
that`s one of your eccentric ideas.

Maybe you would need better drivers for the Festival speakers?
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Old 1st August 2008, 03:06 AM   #7
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Quote:
Originally posted by Lumba Ogir
Wavebourn,
that`s one of your eccentric ideas.

To put in public domain?
Sun Microsystems did that with SPARC technology.

Quote:
Maybe you would need better drivers for the Festival speakers?
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.
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Old 1st August 2008, 05:31 AM   #8
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Wavebourn,
look, I wouldn`t do that either (just was recently reading about these things). Adequate damping is a big problem, in practice impossible in "free-standing" mode. Otherwise, the difference would be huge...
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Old 1st August 2008, 06:51 AM   #9
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Quote:
Originally posted by G.Kleinschmidt
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
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.
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Old 1st August 2008, 06:58 AM   #10
Tim__x is offline Tim__x  Canada
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From the whitepaper it sounds simpler than anything suggested above.
It sounds like it's just a CFP with a cascode on the driver.

Novel.
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