81–90 of 110 posts
> And, of course, we can't change Boltzmann's Constant because Professor Boltzmann is dead[3]. Worth the read just for that punch line.
The opening paragraph of Goodstein's "States of Matter": "Ludwig Boltzmann, who spent much of his life studying statistical mechanics, died in 1906, by his own hand. Paul Ehrenfest, carrying on the work, died similarly in 1933. Now it is our turn to study statistical mechanics."
Earlier quoted context omitted.
I was messing about with contact microphones last year and very much akin area to guitar amps as high-impedance, so very much the same issues. If you run on batteries you will find it works best, as with anything mains, you will want a good ground. What I did find was that if you use peizo's back to back you can effect a balanced signal and that in itself helps immensely in eliminating much of the noise. You can also…
Wait. We have ADCs that produce floats now? That’s amazing.
> In fact, a remarkably common response to a diagnosis of resistor noise is to seek a source of "good" resistors, with "good" being defined as without thermal noise. This is impossible. It's impossible to make a totally noiseless resistor, but it's also important to understand that all resistors are not created equal. Most resistors have noise levels that are orders of magnitude above the Johnson limit. Potentiometer…
Electrical engineer here. Thermal noise is the same for all resistors with a given R, regardless of their method of manufacture. You cannot have thermal noise either less or more than this, so it's not a Johnson "limit" but rather a definite value. You are correct that there are other sources of noise such as 1/f noise. But more importantly, the manner in which noise manifests in the end result has to do with the cir…
Earlier quoted context omitted.
Electrical engineer here. Thermal noise is the same for all resistors with a given R, regardless of their method of manufacture. You cannot have thermal noise either less or more than this, so it's not a Johnson "limit" but rather a definite value. You are correct that there are other sources of noise such as 1/f noise. But more importantly, the manner in which noise manifests in the end result has to do with the cir…
I think you "well actually"'d a bunch of things I specifically didn't say. I use "Johnson limit" synonymously with "thermal noise limit" because they are the same, and it's the limit of how low noise can be after removing all other sources of noise. Most people, if they even learn about resistor noise, will only learn about thermal noise. If they're lucky enough to identify a resistor as the noise troublemaker in a c…
"Metal film or thin film resistors have little excess noise in these tests and thick film resistors show large excess noise"
Earlier quoted context omitted.
Uh, for a looong time already. The LT1028 was available in the eighties and afaik, still unsurpassed (in terms of voltage noise, it's unfortunately a sucker in terms of input current and current noise, so it's for low impedance applications only and it's fairly expensive). The cheaper OP-27 is also old and still available. The challenge is to find a low-noise OpAmp with high input impedance where earlier hybrids with…
Yes, I built a guitar pedal that was designed around JFET gain stages and the JFETs had to be sourced from a specialist. I wonder if they're still being made. Most of the discrete JFETs I see available are for switching applications.
> In fact, a remarkably common response to a diagnosis of resistor noise is to seek a source of "good" resistors, with "good" being defined as without thermal noise. This is impossible. It's impossible to make a totally noiseless resistor, but it's also important to understand that all resistors are not created equal. Most resistors have noise levels that are orders of magnitude above the Johnson limit. Potentiometer…
Electrical engineer here. Thermal noise is the same for all resistors with a given R, regardless of their method of manufacture. You cannot have thermal noise either less or more than this, so it's not a Johnson "limit" but rather a definite value. You are correct that there are other sources of noise such as 1/f noise. But more importantly, the manner in which noise manifests in the end result has to do with the cir…
For other readers: some resistors have much lower flicker noise[1] where “wire-wound resistors have the least amount of flicker noise. Since flicker noise is related to the level of DC, if the current is kept low, thermal noise will be the predominant effect in the resistor, and the type of resistor used may not affect noise levels, depending on the frequency window.”
> And, of course, we can't change Boltzmann's Constant because Professor Boltzmann is dead[3]. Worth the read just for that punch line.
The opening paragraph of Goodstein's "States of Matter": "Ludwig Boltzmann, who spent much of his life studying statistical mechanics, died in 1906, by his own hand. Paul Ehrenfest, carrying on the work, died similarly in 1933. Now it is our turn to study statistical mechanics."
He mentioned something about how resistor noise can actually track with the low frequency portions of the audio signal due to the resistor literally heating up and cooling down as the current through it varies. I thought that was interesting. I knew that noise was proportional to heat, but I didn't realize the temperature could vary that quickly, but I guess it makes sense when you're dealing with tiny parts. There are probably also localized hot spots that have less thermal mass than the entire resistor as a whole.
The interview is posted in this thread: https://www.audiosciencereview.com/forum/index.php?threads/t...
> And, of course, we can't change Boltzmann's Constant because Professor Boltzmann is dead[3]. Worth the read just for that punch line.
The opening paragraph of Goodstein's "States of Matter": "Ludwig Boltzmann, who spent much of his life studying statistical mechanics, died in 1906, by his own hand. Paul Ehrenfest, carrying on the work, died similarly in 1933. Now it is our turn to study statistical mechanics."
My only experience with this is building and designing guitar amps, which often have 80dB of gain or more, a.k.a., a pain in the ass amount of gain to deal with. It's not something on par with, say, radio astronomy, but it's still a lot of gain to deal with. Usually the main source of noise will be a 120Hz or 100Hz buzz, but with humbucking pickups and careful orientation of the guitar you can mostly eliminate that.…
Any reason for guitar pads couldn't use a capacitive divider in place of a resistive divider? (I have no idea what a guitar pad is)