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Old 29th July 2009, 09:33 PM   #1
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Default Aleph (Single Ended) + Larvadin (no Memory Distortion) = Ultimate Aleph?

I have heard about "Memory Distortion" and have read this one
http://www.lavardin.com/lavardin-techE.html
http://peufeu.free.fr/audio/memory/ (overview)
http://peufeu.free.fr/audio/memory/m...-complete.html (complete circuit)
http://peufeu.free.fr/audio/memory/memory-6-test.html (advanced second stage - see Fig. 6.2)

and then I thought more accurately about the Pass Aleph versions
http://www.patentstorm.us/patents/5710522.html Pass Aleph active CS United States Patent 5710522
http://www.pat2pdf.org/ (put in 5710522 for download)
http://www.firstwatt.com/downloads/seclassa.pdf

and I note the follow advantages/disadvantages

1) Larvadin models:
- no memory distortion through cascoded stage and sziklai darlington by input diff gain stage and cascode current source
- no memory distortion through double cascoded stage by second voltage gain stage and cascode current source
- cascode buffer stage as predriver for drive the true complementary push pull output power class B follower
- unfortunately no single ended class A output buffer and no class A push pull buffer
- unfortunately current mirror to create single ended output for first stage (I don't like current mirror)

2) Aleph models:
- no Class AB distortion present through single ended Class A output power common source stage
- unfortunately no cascoded version in both stages
- output power stage (no output buffer stage, i.e. voltage and current gain) instead source follower output stage (advantage or disadvantage ? - I don't know really)

Now I think about various mixed circuit designs of both topologies.
The result must be actually the ideal power amplifier, free from all kinds of distortion. Are there already designs in this kind?
I appreciate about your comments and information.
Thank you very much
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Old 29th July 2009, 11:03 PM   #2
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Hi
Having very similar thoughts - I want to try a single ended (half of an) F5 with cascoded first stage. Alas no time for a couple of months, but eager for any input from the experts.

Cheers
cv
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Old 30th July 2009, 08:41 AM   #3
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No idea what memory distortion might be, but if you like cascoded amps, look at Nelson's Threshold amps.

Have fun, Hannes
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Old 30th July 2009, 11:32 AM   #4
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I've been thinking about how to reduce such things for a while. One easy way is to spend many times more $$$ on devices with very low temperature coeifficients like metal foil resistors (2-5ppm). Other ways sometimes might include using over rated parts By that I mean using a 2W device where only 1/4 may be necessary. Also, designing the circuit so that under operation the signal range is a very small pecentage of the whole. I guess that's another Basically build a circuit that swings 30V and 100mA but only use it for 3V and 5mA lots of Headroom
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Old 30th July 2009, 12:28 PM   #5
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I owned the Lavardin IT amp a few years back. It was unusal in that it had a midrange that was very natural and real...valve like. It was also very musical and had a good bottom end. It did lack top end extension and air despite numerous equipment changes.

But yes i do remember it well as one of the best solid state amps that i had lived with.
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Old 30th July 2009, 01:58 PM   #6
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Quote:
Originally posted by flg
Also, designing the circuit so that under operation the signal range is a very small pecentage of the whole. I guess that's another Basically build a circuit that swings 30V and 100mA but only use it for 3V and 5mA lots of Headroom

I've been learning the same thing in my simulations. It makes for a very smooth sound...
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Old 30th July 2009, 03:29 PM   #7
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Quote:
Originally posted by audiojoy
I owned the Lavardin IT amp a few years back. It was unusal in that it had a midrange that was very natural and real...valve like. It was also very musical and had a good bottom end. It did lack top end extension and air despite numerous equipment changes.

But yes i do remember it well as one of the best solid state amps that i had lived with.
"It did lack top end extension" ... typical effect of complex distortion (crossover distortion mainly create through only 20-50mA in the output stage. This distortion mostly audible above 2000 - 3000 Hz.


"Basically build a circuit that swings 30V and 100mA but only use it for 3V and 5mA lots of Headroom ......."

This is one of the main reason why in most cases tube amplifiers sound better than such with transistors (solid state amplifiers)
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Old 30th July 2009, 04:34 PM   #8
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Quote:
Originally posted by tiefbassuebertr
This is one of the main reason why in most cases tube amplifiers sound better than such with transistors (solid state amplifiers)
This would be true if the tube amplifiers were operated that way, but
when you look at real power amplifier circuits, this causes such
inefficiency that power stages must be operated to the extremes
of voltage and current. They do not have the luxury of staying in
a small space on the load-line range.

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Old 30th July 2009, 05:33 PM   #9
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That particular mode I mentioned is ussually difficult to achieve at the output. You would be getting unbelievably low efficeincy and have more heat than sound, etc. etc... Although N.P. has a Pat. along those lines that improves the situation.
It's not to bad in a preamp (VAS) circuit though. I'm getting ready to play with another proto of such a device. Burns almost 50W a channel
But, the real difficulties are in the semiconductors. We don't really have all that much choice of die size or Pd and linear operating points vs desireable input characteristics.
I'm not ready to talk about my doo-dad but I'll tell you it's a VAS kinda circuit with an LU1014D gainstage on steroids Maybe a cross between a BOZ and a ZV8. I'm hopping to drive an F4 with it
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Old 30th July 2009, 05:44 PM   #10
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IMHO, about the tube designs dealing with clipping, and headroom, is the "softness" of the clipping and the Spectra of the furrier(You Know Who) you end up with (among other factors). Sand stuff ussually drives right up/down to saturation and turns your music into Jimmy Hendrix momentarily(almost square waves). You could have unmeasureable THD at 5W and 25% THD at 10W(Square waves are 33% THD). Music easily contains that dynamic of a range but finding a way to include all the dynamics of music into a "test", we still seem to be working on...
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