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A very good article about amp musicality vs measurement
A very good article about amp musicality vs measurement
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Old 8th March 2018, 12:40 PM   #11
anti is offline anti  Slovakia
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Gnfb amp will almost universally sound more compressed and possibly sounding better with electronic music.
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Old 8th March 2018, 12:59 PM   #12
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by xrk971 View Post
Suppose you have two amps both with, say 10ppm THD (I know, I know, 10ppm is so pedestrian with zero distortionistas ), and one uses no global feedback, whilst other uses lots of it to achieve same 10ppm THD - what is the effect on our perception to the music produced, all else being equal?
Do you mean all the other forms of distortion being equal?
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Old 8th March 2018, 01:10 PM   #13
scottjoplin is offline scottjoplin  Wales
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Hi destroyer X, I presume you are aware of Nelson Pass' designs
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Old 8th March 2018, 01:38 PM   #14
PMA is offline PMA  Europe
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Well known 20 years old article . Interesting that the thread starter wants for us to discuss it now (again). Not only we have (IMO) much better articles on topic, but also there are much better circuit solutions known now that those 20 years ago, which were mostly "distortion creating effect boxes". Some like it distorted, I agree.
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Old 8th March 2018, 01:43 PM   #15
PMA is offline PMA  Europe
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IMO the biggest improvement in sound (speaking about good recordings) now, compared to situation 20 years ago, is because of huge improvement of digital sources. Now we can make a choice of very decent D/A converters and they, with a good 96/24 source program, are able to give us fantastic sound quality. There is no need for added colorization anymore and the most accurate components give the best sound, in case they are also well engineered regarding EMI immunity.
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Old 8th March 2018, 02:20 PM   #16
billshurv is offline billshurv  United Kingdom
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A very good article about amp musicality vs measurement
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Old 8th March 2018, 02:57 PM   #17
john_ellis is offline john_ellis  United Kingdom
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It would be necessary to dissect the amplifier circuits Mr Collom set up and get the data to know what lies behind his aural listening results. Many amplifiers of that era may have had distortion levels around 0.1%- just detectable. However, IMD is more important than THD IMHO as that seems to me to lead to signals that might be called unclear - generating distortion signals that were not originally present. With 0.1% or so THD, IMD could be higher.
With today's fast transistors and wide bandwidth amplifiers with THD around 0.001% IMD has almost vanished too. I doubt that the comparison would work with todays best circuits.
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Old 8th March 2018, 03:49 PM   #18
stocktrader200 is online now stocktrader200  Canada
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if you want the sound of no feedback, add a 3 - 5 ohm resistor inline to the speaker. nfb gets rid of crossover distortion primarily in a class AB amplifier. Tube amps and class D amps have their best performance below 5 watts. Class AB has it's worst performance at these levels
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Old 9th March 2018, 01:53 PM   #19
Bigun is offline Bigun  Canada
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A very good article about amp musicality vs measurement
Feedback changes many things, there are so many variables that to correlate sound with feedback only gives us limited guidance. It's been pointed out that feedback affects the output impedance - but you can design a feedback network to give you a wide range of output impedances so no general conclusions would be safe.

Like all aspects of amplifier design, any tool used poorly gives poor results. Some feedback is inherent (e.g. Triodes, as mentioned already) and some is created (traditional loop feedback) - it's how you apply it that matters.

I think there have been significant changes affecting quality of sound reproduction from many different things: quality of components (capacitors are now superb c.f. 50 years ago), speakers (not only better drivers but better boxes), semiconductors (higher gm and lower parasitics), music storage.

If only the quality of recording was more consistent, but as always, it's an industry driven by $.
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Old 9th March 2018, 02:56 PM   #20
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Really don't get the point of this old thread coming up again. We have advanced quite a bit on our knowledge of feedback and can make amps with vanishing low levels now.

I know I have heard "very good" sounding amps that didn't use much if any feedback and those that used as much as possible. Do not see any reason at all do demonize either one. Build or buy what you like.
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