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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 22nd November 2018, 06:17 AM   #10111
PMA is offline PMA  Europe
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Quote:
Originally Posted by DPH View Post
Similarly, I need lower gain (unity?!) amps around here. Nearfield and quiet.
It seems that most of us listen at quite low SPL level. You might like to use a unity gain class A power buffer then. You get both noise and distortion as low that there is no reason to speak about it. With a preamp that usually has gain like 5x (14dB) you would probably cover the SPL you need.

Just a small warning, in case you often listen to classical music, many pieces have so low average level that you need overall gain at least as I have mentioned, otherwise it will sound too silent.

Interestingly why do we mostly speak about "steamroller" amplifiers here, if the demand seems to be for lower power and lowest possible noise? No trivial answers, please.
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Old 22nd November 2018, 06:26 AM   #10112
gpapag is offline gpapag  Greece
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by simon7000 View Post
You know perfectly well bells are a ratio and without a reference meaningless

Hi Ed
I understand what 110 dBA or 110dBC (fast or slow) means .
But what this lower case a stands for in these:
110dBa with a fast response "C"
110dBa slow "A" weighted

George
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Old 22nd November 2018, 08:34 AM   #10113
scottjoplin is offline scottjoplin  Wales
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Originally Posted by mmerrill99 View Post
The bit about "helps with our ability to create the illusion in our rooms if we expose ourselves to sound in the natural world, i.e. outdoor spaces" I'm not sure is correct. We've already laid down the sound patterns & behaviors of how sound objects behave in nature - maybe additional exposure helps to remind/reinforce these patterns but I doubt it - the learning has already done its job to completion.
Yes, that's right, he says it does, a good reason to get out more and stop reading books about audio perception and just do it.
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Old 22nd November 2018, 09:40 AM   #10114
TNT is offline TNT  Sweden
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Originally Posted by scott wurcer View Post
Randi got poor advice in setting up his challenge. IIRC he left the door open for someone to choose pathological combinations of speaker/amp/cable where easily detected frequency response anomalies could occur.
Still, no one claimed it.

//
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Old 22nd November 2018, 09:47 AM   #10115
TNT is offline TNT  Sweden
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Do you use this description of the hearing process as input when designing your products?

If so, how?

//

Quote:
Originally Posted by mmerrill99 View Post
Yes, I saw Linkwitz was aware of Bregman & auditory scene analysis (ASA) but does he only reference it in relation to room acoustics - you seem to also limit it to this consideration or have I picked this up wrong?

ASA is really a fundamental & core aspect of what our sense of hearing is about - what enables us to make sense of complex acoustic mixtures in order to best represent the real world & arrive at percepts corresponding
to the individual sound sources or follow, for instance ,a single melody in the midst of an orchestra.

"The task is also known as the ‘cocktail party problem’ [4], which refers to the ability to follow one conversation when many people are talking at the same time. The auditory system has to determine whether a sequence of
sounds all came from a single source, and should be perceived as a single ‘stream’ or whether there were multiple sources [5]. In the latter case, each sound in the sequence has to be allocated to its appropriate source and multiple streams should be heard."

As I said before this is a highly complex task & the fact of the matter is that there is not enough data (nerve impulses arriving on the auditory pathway) to uniquely solve this task i.e to uniquely match the signals to one particular auditory scene - it's an ill-posed problem that suffers from a poverty of stimulus. So at any point in time the auditory scene is the result of some guesswork & we are constantly in somewhat of a confused condition which we try to alleviate by using different techniques - techniques that we are only discovering but the easy ones to understand are - using other signals from other senses to corroborate with auditory signals - so vision is an important source of additional signals.

Other techniques used are predictive top-down guesswork selecting a finite set of previously stored patterns which best match the pattern of incoming auditory signals. Top-down matching isn't just a passive process, it actively directs the bottom-up signals by focusing attention to specific aspects of the evolving sound. And bottom-up signals can cause changes to the set of patterns that best corroborate with the signals - it's a two way communication.

So attention, inattention & previous experience also play a part in what is being heard, what aspects are being heard - like vision, we don't consciously hear what is outside our focus.

There's lots more to be said but the result of all the above is that auditory perception is fragile (as are other perceptions) hence we can experience auditory & visual illusions - it also explains why even when there is an obvious audible difference, we often don't score 100% in identifying this.

A lay persons guide makes an interesting read about the ambiguity of auditory perception & the use of illusions in the study of this perception, with particular emphasis on music perception

ASA: the sweet music of ambiguity
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Last edited by TNT; 22nd November 2018 at 09:55 AM.
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Old 22nd November 2018, 09:57 AM   #10116
Jakob2 is offline Jakob2  Germany
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Originally Posted by TNT View Post
Still, no one claimed it.

//
Maybe the reason for this fact is:

The James Randi Educational Foundation's Million Dollar Challenge has been terminated.
(source:The Million Dollar Challenge - JREF)

a more detailed description of the situation:

JREF Status - JREF
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Old 22nd November 2018, 10:21 AM   #10117
Jakob2 is offline Jakob2  Germany
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Originally Posted by scott wurcer View Post
Randi got poor advice in setting up his challenge. IIRC he left the door open for someone to choose pathological combinations of speaker/amp/cable where easily detected frequency response anomalies could occur.
Simply no, as no further negotations about the specifics were done. Randi "weaseled" out, which means from an objective point of view he was not acting in goog faith, used dubious statements as arguments and violated/changed the rules of the JREF challengs during the back and forth with Michael Fremer.
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Old 22nd November 2018, 11:05 AM   #10118
simon7000 is offline simon7000  United States
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George,

It means I am old and slipping into old habits. It should be upper case. A bit back I managed to stop using kilocycles etc. when folks mentioned that it was replaced by the non descriptive tag of kilohertz almost 60 years ago.
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Old 22nd November 2018, 11:19 AM   #10119
simon7000 is offline simon7000  United States
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Pavel,

If one has inefficient loudspeakers and listens near field the background noise may be matched at the listener's ears by a power level of a milliwatt or two into the loudspeakers. To clearly hear a soft passage you would want about a tenth of a watt going into the loudspeaker. Even better would be a full watt or so. So the maximum power issue becomes what dynamic range is available on the recordings you are listening to.

In practice live music follows the same signal to noise ratios. You would probably not enjoy a concert where you could not clearly hear the soft passages. That would set the lower limit of the possible dynamic range of a recording. The upper limit would be how loud a human can make an instrument sound.

Been a while since I measured that but it would be at least 4 bells. So add 4 zeros to the power requirements! Maybe even 5!
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Old 22nd November 2018, 11:30 AM   #10120
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Quote:
Originally Posted by simon7000 View Post
Pavel,

If one has inefficient loudspeakers and listens near field the background noise may be matched at the listener's ears by a power level of a milliwatt or two into the loudspeakers. To clearly hear a soft passage you would want about a tenth of a watt going into the loudspeaker. Even better would be a full watt or so. So the maximum power issue becomes what dynamic range is available on the recordings you are listening to.
Ed, this is more than obvious to most of us, I would say. However, I know there is a huge difference in the listening level chosen by my various visitors, even if we listen to the same recording. Some of them prefer to listen at so high level, that my 200W amp gets close to clipping in fff peaks (85dB/2.83Vrms/1m speaker sensitivity). Some of them listen at level that 2W are barely attacked. So if Daniel says he listens at low volume level, I am suggesting a class A unity gain power buffer + preamp, provided that he uses something like 85-90dB/2.83V/1m speakers.
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