Do you have any idea why the noise of the 1K termination rises again towards higher
frequencies? ( 100 Ohm also, but less)
In my preamp, I have a switchable termination of 60 Ohms directly in the shielded box.
That gives a very convenient absolute 1 nV/sqrt Hz calibration line on the spectrum
analyzer display, and it is completely flat to 1 MHz where the gain starts to drop.
cheers, Gerhard
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I wish TI provided a plot of input current noise versus frequency for the LME49740 (I assume 79740 was a typo).
Not a particularly good choice for MM with that current noise, despite their application example!
Some can survive, but most can't. 37 C is too hot for comfort.
By night, this typically drops to 27-29 C, which not too bad, especially with a nice breeze.
My room is typically 4-5 C higher than the outside, the rest of the apartmen is 1-2 C above the outside once the concrete heats up.
Yes I found a shorted trace and the issue is now gone. I figure the 100 ohms is 1.3 nV/sqrt Hz.
I get nowhere near 1 Mhz. More like 50,000 Hz. But I strongly suspect I can get noise around 100 pV/sqrt Hz 1,000 to 20,000 hertz. This was more a test of concept with the multipilier.
I think you are still the champ.
Attached current schematic.
Attachments
Do you mean the input to the whole unit or the voltage at the speaker terminals?
It is easy to limit the input voltage to an amp without affecting performance at normal input levels. If you limit the input you also limit the output and therefor the voltage at the speaker terminals.
However how the speakers are handled during limiting makes a big difference sonically. Some amplifiers sound terrible when they clip, but with other amps you hardly notice unless it's really bad. Clipping at the input of an amp can sound worse than clipping at the output.
Why not use a psychological tool, like turning on a red diode when the peak level reach a point (under the amplifiers limits) were it can be dangerous for the speakers ?
Breaking some speakers, you could write a safety curve (Duration/V) and simulate this curve with some ICs to shunt down the input signal when ti begin to be dangerous for the peskers ?
At least, you don't have to protect your amps from short circuits of their outputs ;-)
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All it seems to take is a group of great minds it seems! Kean, yes I was thinking if you could limit the input voltage to the amp so it would only be able to have a certain max output at the amp output to the speakers. Christophe that seems like a good idea to have a simple led that would flash or stay on when the limit is reached. Brad thanks for confirming that this is not only possible but could be done without causing some other problems. I know I have been guilty of doing this myself, pushing the speakers to the point that the suspension just ran out of movement, up to that point no problems with distortion and then ugh, that awful sound.
If it was so easy then why do so few members here not sell to this vast market of money where people that enjoy technobable literally toss money around? Anyone can go to school and learn how to make a low distortion amplifier with low noise. Whether anyone wants to listen to it at all is another story. Even Nelson Pass can't predict which of his DIY releases people will prefer, before he himself hears it; and yet it remains a guess. And that crowd, is this crowd.
even John Atkinson has no idea why the subjective reviews can be superlative when he sees what should be clearly audible flaws in some pieces over his decades of measurements done alongside most equipment reviews at Stereophile
seems accuracy isn't what everyone wants or buys - so the mistake is reasoning from the winners of the fashion, marketing game
and Psychoacoustic researchers have put in the effort, the controlled testing that leads to the conclusion that for valid listening tests finding quality, "transparent" electronics is not at all difficult
this is relative to where it is worth looking at human hearing with the scientific method
for home audio reproduction it really is speakers, their characteristics of frequency response, directivity, room effects - with maybe some times a bit of their distortion properties if Geddes is near right
as a electronic design pro I consider diyaudio electronics an entertaining hobby - if I wanted to advance the quality of my music listening experience I would work on the room and speakers end
seems accuracy isn't what everyone wants or buys - so the mistake is reasoning from the winners of the fashion, marketing game
and Psychoacoustic researchers have put in the effort, the controlled testing that leads to the conclusion that for valid listening tests finding quality, "transparent" electronics is not at all difficult
this is relative to where it is worth looking at human hearing with the scientific method
for home audio reproduction it really is speakers, their characteristics of frequency response, directivity, room effects - with maybe some times a bit of their distortion properties if Geddes is near right
as a electronic design pro I consider diyaudio electronics an entertaining hobby - if I wanted to advance the quality of my music listening experience I would work on the room and speakers end
I think it is obvious that we can't fully trust reviewers' words as they rely on these suppliers to make a living. Often I had to try to read between the lines for "codes" showing where the reviewer didn't really appreciate the product.
Sometimes, I can see a good new product got a "bad" review just because it is a "competitor" to the big sponsor of the magazine. I can see the reviewer tried hard not to say good words and even in the measurement, something that should show how good the product is not shown.
When customers really understand the measurement, I don't believe they will ignore it. The question is whether the customers understand what the charts mean. They only understand the words.
If the reviewers say good words about a product. Then there is bad measurement of the product. Then comes along the measurement conclusion, a good words concurring with the previous reviewers, then who will think that the measurement is bad????
Sometimes when I give print artwork/designs to my clients, they seem to find things which were not put in the first place by me
.
I guess perception of sound may be the same. Meaning in art.
But I also find technical aspects of audio more interesting.
Regards.
I guess perception of sound may be the same. Meaning in art.
But I also find technical aspects of audio more interesting.
Regards.
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Who's to say the problem isn't the original recording leaving out whatever, however, and varied designs correct this to some degree?
There's very accurate amps people like and hate. I wouldn't call it a good way to distinguish based on humans being flawed. Who the **** wants to make audio reproduction we assume some other entity would enjoy? It's like music itself is meant to be "accurate"; even well notaded classic music is up to interpretation for enjoyment. It's hard to believe we should desire for playback not to be related to subjectivity.
Perhaps some day we'll have measurements that people can use to predict, without needing to be an expert reviewing a network analysis of a variety of samples, if people will like it. Class D often is extremely accurate, and yet never sounds truly like anything but class Dead to me - sure sometimes I appreciate some amps abilities but the minute I go back to something else I realize why I call it class Dead.
There's very accurate amps people like and hate. I wouldn't call it a good way to distinguish based on humans being flawed. Who the **** wants to make audio reproduction we assume some other entity would enjoy? It's like music itself is meant to be "accurate"; even well notaded classic music is up to interpretation for enjoyment. It's hard to believe we should desire for playback not to be related to subjectivity.
Perhaps some day we'll have measurements that people can use to predict, without needing to be an expert reviewing a network analysis of a variety of samples, if people will like it. Class D often is extremely accurate, and yet never sounds truly like anything but class Dead to me - sure sometimes I appreciate some amps abilities but the minute I go back to something else I realize why I call it class Dead.
I'm not sure I get your point. This is diyAudio, where build traffic reigns.
Improved accuracy is a very noble goal. I would even say it is true to the precise meaning of "hi-fi." (Fidelity to high-fidelity... my head is starting to spin.) But I don't think that that has been proven to equate to "life-like" (or "live-like"), which is the goal of many audiophiles also.
It seems to me that you are in danger of throwing the baby out with the bathwater. Like the Pendulum that has swung too far?
And your comment about speakers? As somebody who actually designs them, I want the best amplifier to drive them. I want the best source component to deliver and I want the best recordings... looks like a pattern to me?
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