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View Poll Results: Do You Think Single-Ended Class-A Amplifiers Sound Best?
YES! 185 44.47%
NO! 77 18.51%
Nothing Special. Just Another Amplifier. 86 20.67%
I Haven't Seen Such An Amplifier. 68 16.35%
Voters: 416. You may not vote on this poll

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Old 26th August 2009, 06:13 AM   #21
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Quote:
Originally Posted by audioman54 View Post
I attached a graph of THD vs Power for my 130 amp Demo unit based on the LME49811.
Lumped THD has little correlation with sonics... do you have some spectrum graphs?

dave
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Old 26th August 2009, 06:45 AM   #22
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Hi Dave,

Yes I did have a lot of spectrum-based graphs for that amplifier... but alas they are all on my computer at National. I have been trying to purchase a used AP2 cascade for my home lab to make my own measurements but have been unable to find one at a price an "Out of work analog/audio applications engineer" can afford!

However I might be able to dig up a few graphs. Which parameters/settings would you like to see most?

One other thing, during our listening tests we found that if the entire THD line, like in the graph I showed, dropped an equal amount from low to high power out it was always an audible improvement! But it had to be a constant difference from low to high power. There were also some things we looked for in the spectral plots, which had to do with the shape of the peaks of the individual harmonics from 20 Hz to 20kHz (or 200kHz).

Mark / Audioman54
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Old 26th August 2009, 07:37 AM   #23
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I've heard very good SE class A triodes and pentodes, as well as very good PP varieties.... "Nothing Special. Just Another Amplifier" was as close to my feelings on the matter, though not accurate... each has it's own special place, especially with various speakers.

Cheers!
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Old 26th August 2009, 07:51 AM   #24
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Default AP2 FFT for LME49811 mono amplifier

Planet10,

It took a hour or so to find this FFT AP2 file for a LME49811 mono power amp and it is not a perfect file because I don't have all the setup data for it. I believe it was a 0dB (which was 1%THD for us) 1kHz sine wave into an 8 ohm load. See the attached AP2 Plot.

Sorry but this is the only one I could find.

Mark / Audioman54
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File Type: jpg 49811.JPG (58.8 KB, 327 views)
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Old 26th August 2009, 04:38 PM   #25
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I don't know why people rely on Fourier transforms, as if it is a well known fact that we transform what we hear into harmonics... Harmonics under noise floor absolutely don't mean errors are under the floor of perception!
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Old 27th August 2009, 08:04 PM   #26
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Quote:
Originally Posted by audioman54 View Post
It took a hour or so to find this FFT AP2 file for a LME49811 mono power amp and it is not a perfect file because I don't have all the setup data for it. I believe it was a 0dB (which was 1%THD for us) 1kHz sine wave into an 8 ohm load.
So that is near full power? Pretty good.

More important is what it looks like at realistic power levels and how it changes when you turn up the wick.

A family of curves from about 50 Hz to 5kHz, at power levels from ~ 10mW to a watt or 2.

dave
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Old 27th August 2009, 08:37 PM   #27
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Quote:
Originally Posted by planet10 View Post
More important is what it looks like at realistic power levels and how it changes when you turn up the wick.

dave
From recently measuring a Gainclone I'm more curious how it changes when the frequency is wicked up. The LM3875 chip's distortion spectrum gets 'toothy' fast.
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Old 29th August 2009, 04:28 AM   #28
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I voted , but I prefer Class A Push-Pull .
My oppinion !!

Regards,
Carlos
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Old 29th August 2009, 02:06 PM   #29
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SE class A amps don't have crossover distortion of class B (and to a lesser extent class AB) or the RF and posible noise issues of class D. However the better question would be is SE class A worth the extra power consumption and cost (big transformers and heatsinks). I would say for >10Watts it's not worth it, for headphone amps for non portable usage definatly worth it. For anything inbetween it depends ^ ^
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Old 30th August 2009, 10:17 AM   #30
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Personally i voted YES, as the best sounding most pure amp i have built so far is a single ended monster hybrid. However, i think classD is fast catching up and as soon as we learn how to truly remove all background noise and carrier leakage the classD mode of sound reproduction will become king. For the moment it is just a prince in the shadows of the mighty CLASS A ( and rightly so too )
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