Methinks you thought wrong, Max. It is a very rare effect, few make it up to there, and the least represented subrgoup of those who do make it are owners of High End stuff. Of course, it's not the devices, it's them, they live in a la-la world in which as long as it's famous and expensive, it plays great music and the usual caveats of putting together a good SYSTEM do not apply to them. Those with lesser gear are much more inclined to look the truth in the eye and admit some device dos not do a good job.
Dan
I wish you good luck with that testing.
Very low and sub Hz frequency territory (where you are interested at, if I have understood correctly) is not an easy area to work on, as the target 1/f noise -due to the CC resistors- output of the bridge will be of single digit uV amplitude.
In addition to all the ‘close to DC’ parasitic noise sources of the circuit (thermal imbalance, galvanic, dissimilar metals), you have to think of the DC source purity too.
You may have to find a way to monitor and record all the other noises of the circuit except the noise due to the two carbon composition resistors.
Concurrently monitoring/recording two identically built bridges – one with carbon comp R3, R4 the other with metal film R3,R4 with both bridges fed from the same DC source - seems to me a simple way to achieve this.
George
Those puppies are great. Ours has an annoying habit of pulling multiple pages at a time from the hopper no matter how you fan the stack, what a pita.
jn
We have one of those too, you might need a set of replacement rollers installed to stop that.
In the office where I worked was a photo copier on a trolley/cart with enclosed paper storage below.
Inside was a 15W globe to keep the paper stocks warm and dry.
This cured all paper jam/multi sheet feed in problems.
Dan.
Thanks for the well wishes.
Yeah, I figure on a temp controlled metallic shielding enclosure.....
And very long term FFT sampling/averaging.....
And dead clean DC.....
And dead clean/regulated AC supply.....
And.....
And.....
I am not sure that I need to go to <<< 1 Hz frequencies, but it won't hurt to do so if practicable.
I am also going to try mixing variable levels of LF 1/f noise in with known music in order to subjectively better understand the sonic damages caused.
Ime, typically pink noise does not sound as it should.
I have tried auditioning a pink noise cd and applying a ferrite clamp-on filter and another clamp-on filter with different ingredients (line level cabling).
The subjective results were interesting.
The ferrite increased bursting/memory distortion/tailing type effects, and the other filter caused the pink noise to sound matter of fact/clean and without false embellishment.
The BQP did similar, but added extra colour/flavour of sorts.
Another experiment on a big outdoor show caused the ground to shake when running up sub arrays.
Concurrently running dual bridge/in amp stages is a good idea, thanks.
I intend to get to the bottom of this !.
Dan.
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If you used the exponential approximation equation, your result is too high by a factor of 2 to 3, I'd guess in the 1% range at most.
If you include proximity effect, the result may be too low. I've no idea what it'll be at 20Khz that wire.
If you want group delay, you'll have to consider the drive, load, and cable impedances, as well as prop velocity and length.
Waaaaay over my head...
jn
It isnt of interest nor concern to most people..... But as the freq go higher than audio, it becomes a serious issue.... I would be more concerned with ADC/DAC circuits where the issue of speed, impedance and waveform fidelity can be upset by many such details.
-RNM
I've read many times that thick film SMD resistors are more 1/f noisy than old CCs.
Read this link with some good data (and the references)
CoDesign • Second Thoughts on Electronics • Theory • All the noise in resistors
With proper dual bridge/INAs set-up, many extraneous influences will be diminished in importance.
George
Attachments
Indeed it is unusual, which is a great irony - it is in fact an excellent marker of a system working "correctly", which simply means that the level of audible distortion is at a low enough level that all the information from the original, recorded event can be assimilated by the brain working in a relaxed mode, all the auditory cues from echos, etc, in the spaces where the microphones were located can be unscrambled, and a "big picture" of what was captured in the recording forms without conscious effort. This means that extremely complex recordings, with high levels of acoustics information embedded intentionally, or otherwise, become amazing places "to visit" - takes your breath away!
The pity is that this capability for audio reproduction is largely ignored, mainly because most are oblivious of the possibility of it happening - the equipment itself virtually always has the capability to perform the "trick", but the system made up from these items is normally insufficiently "debugged" to pull it off ...
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Curious that you think that it is 1/f noise, that does not compute for me - however, I certainly can't say that I understand the behaviour, so don't let my twittering put you off doing experiments, your way
...
"See what's left of it" ? ... don't quite follow there ...
Usually what happens is that bits get added, that shouldn't be there - think of a stew, of food, of exactly the right ingredients to give the right flavour - then someone pops into the kitchen and throws in a few bits and pieces of whatever comes to hand, purely at random, as extras. Your job, should you choose to accept it, is to precisely register the "correct", intended taste in your mouth when you sample the broth ...
Usually what happens is that bits get added, that shouldn't be there - think of a stew, of food, of exactly the right ingredients to give the right flavour - then someone pops into the kitchen and throws in a few bits and pieces of whatever comes to hand, purely at random, as extras. Your job, should you choose to accept it, is to precisely register the "correct", intended taste in your mouth when you sample the broth ...
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Thanks, Frank, I've got it now - and yes, the soundstage, and timbre should remain subjectively identical, irrespective of the volume - one of the confirmation tests I do is to raise the level to the maximum level, at onset to audible clipping, etc - and then drop the volume right down to the lowest level that the attenuator can competently handle ... the presentation should remain completely consistent through that exercise.
Hi,
Indeed, it should. Yet rarely ever does would you not agree?
So, I wonder what happens? What causes it and how do we measure it. What does it take for this NOT to happen?
Not so long ago I read things on here stating that a soundstage is just an illusion. Sure enough, soundstages can be created in the studio to achieve such an illusion.
Yet I've owned and still own recordings that are no illusion and were never intended to be that but a decent copy of an event. A recorded copy of a work of art and surely flawed copy at that. And yet with the right system a rather believable copy, one that contains an image of the emotions felt at the time of recording.
Now, I don't mind some types of distortions much, I don't mind bandwidth restrictions much, what I do mind are distortions that rob music of its emotional content for those are the distortions that turn art into a meaningless product, a product that brings no joy, no pleasure at all.
Sorry for the rant but to my mind that is what it should be about and not a headless chase for ever lower distortions (as we known them) or ever increased bandwidth.
Best,
Indeed, it should. Yet rarely ever does would you not agree?
So, I wonder what happens? What causes it and how do we measure it. What does it take for this NOT to happen?
Not so long ago I read things on here stating that a soundstage is just an illusion. Sure enough, soundstages can be created in the studio to achieve such an illusion.
Yet I've owned and still own recordings that are no illusion and were never intended to be that but a decent copy of an event. A recorded copy of a work of art and surely flawed copy at that. And yet with the right system a rather believable copy, one that contains an image of the emotions felt at the time of recording.
Now, I don't mind some types of distortions much, I don't mind bandwidth restrictions much, what I do mind are distortions that rob music of its emotional content for those are the distortions that turn art into a meaningless product, a product that brings no joy, no pleasure at all.
Sorry for the rant but to my mind that is what it should be about and not a headless chase for ever lower distortions (as we known them) or ever increased bandwidth.
Best,
Frank, I'm totally on your side here, ...
What happens, on the positive side, is that at all times the masking of remaining distortion, by the "data" of the musical event, is effective enough for the mind to accept the validity of the illusion. Unfortunately, our hearing is very acute,, and the "mask" can easily slip just slightly askew, and the illusion collapses - the system has to maintain above a standard of replay, at all times, for the illusion to survive!
The measuring is easy, by the ear - but I'm quite certain it will be very difficult to get numbers, from some measuring tool. It is about distortion, this most certainly is the beginning and end of it, but the usual numbers are almost completely meaningless as a means of measuring the competence of the system to get there.
That said, there should still be concerted effort towards understanding this - say, by assembling a system that consistently performs at this higher level, and then meticulously measuring every aspect of its behaviour ...
...What happens, on the positive side, is that at all times the masking of remaining distortion, by the "data" of the musical event, is effective enough for the mind to accept the validity of the illusion. Unfortunately, our hearing is very acute,
, and the "mask" can easily slip just slightly askew, and the illusion collapses - the system has to maintain above a standard of replay, at all times, for the illusion to survive!The measuring is easy, by the ear - but I'm quite certain it will be very difficult to get numbers, from some measuring tool. It is about distortion, this most certainly is the beginning and end of it, but the usual numbers are almost completely meaningless as a means of measuring the competence of the system to get there.
That said, there should still be concerted effort towards understanding this - say, by assembling a system that consistently performs at this higher level, and then meticulously measuring every aspect of its behaviour ...
very nice link and the reference that Scott gave tells all by brand and thin/thick/smd/th. Very nice.
I didnt test for as many brands on a Quan-Tech resistor noise test instrument I have here but similar results.
What affect would the higher noise at low freq have on operation at mid and higher freqs?? ...On a high resolution audio ADC ??
THx-RNMarsh
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