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Old 27th November 2012, 08:48 AM   #5671
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Quote:
Originally Posted by Bruno Putzeys View Post
Pink noise will put exactly equal amounts of power into the three ranges.
20/20 Mr Bruno (as usual and we can feel your jubilation when it is about poles. )
That is something which always has surprised-me, this difficulty to generate a pink noise with those ugly filters.
This energy repartition (1/ƒ noise ) is pretty natural in many physical or biological systems, and our senses works near that way...
When pink noise appears in electronic devices (Flicker noise ) it is always where you don't want because the corner frequency is set by Mr Murphy.
nb: Zeners are pretty noisy, and can be used to generate white noise more easily than with resistances, despite the amp noise itself is not so boring when amplifying resistance noise. ;-)
Mr Murphy allow us to use zeners in power supplies and other reference voltage stages, where we want... No noise.
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Last edited by Esperado; 27th November 2012 at 09:03 AM.
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Old 27th November 2012, 09:13 AM   #5672
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is it necessary that the noise is generated by analog means? FFT filters make arbitrary frequency response possible. or, in other words, what am I missing?

Quote:
Noise voltage goes up with the square root of R. Suppose you have an amplifier with a 100k resistor strapped across it. Measured over the audio range the amp sees 5.6uVrms noise. Suppose you then connect a low resistance source, say 10 ohms. Total resistance, pretty much 10 ohms. The amp now sees only 56nV.
I think Bruno is trying to politely let us know that maybe our DACs have too high output impedances
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Last edited by mr_push_pull; 27th November 2012 at 09:17 AM.
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Old 27th November 2012, 11:11 AM   #5673
robbbby is offline robbbby  Canada
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Quote:
Originally Posted by barrows View Post
I am confused: I thought you said that with the inputs shorted, there is no "bad" sound at the tweeters? If this is the case, then there is no problem with your amps. When then input is shorted, it stops RF pickup through the input (from airborne sources).
I also am a little bit confused by your use of the words "static" and "white noise". Static, I would describe as a scratchy sounding noise, not smooth in nature, with a definite rough texture. White noise, on the other hand, would be a very smooth, even sounding noise, with no texture: by definition I believe white noise is comprised of an even distribution of noise all across all frequencies, with no one frequency at a higher level than another, it should be smooth and even.
In my experience, the self noise of the nCores on their own is smooth and even textured very soft hiss, what I would describe as white noise at an extremely low level. A static like sound, would indicate a possible problem if you had that sound with the input shorted. With the inputs open, they are available to pick up airborne sources of RF, and I would not necessarily conclude that there is a problem, even if you hear a rough noise floor.
Sorry, i would describe it as white noise, it's just a even sound.

And yes with inputs shorted no sound, but open (nothing connected, no dac, no preamp), I get the white noise.
So this is totally normal with nothing plugged in? The input should take care of that noise? So if it still makes white noise with my combination dac/pre plugged in, the noise is because of my dac?
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Old 27th November 2012, 11:19 AM   #5674
Julf is offline Julf  Europe
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Originally Posted by robbbby View Post
So this is totally normal with nothing plugged in? The input should take care of that noise? So if it still makes white noise with my combination dac/pre plugged in, the noise is because of my dac?
I would make one more test - I would try a 1Kohm resistor between the - and + inputs on the input XLR connector to see if the noise goes away.
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Old 27th November 2012, 11:21 AM   #5675
Julf is offline Julf  Europe
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Originally Posted by robbbby View Post
And yes with inputs shorted no sound, but open (nothing connected, no dac, no preamp), I get the white noise.
Oh, and one more thing - could you try disconnecting the input cable from the nCore (connector J9) to check if the noise changes?
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Old 27th November 2012, 11:28 AM   #5676
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Originally Posted by robbbby View Post
So this is totally normal with nothing plugged in? The input should take care of that noise? So if it still makes white noise with my combination dac/pre plugged in, the noise is because of my dac?
if you have a high output impedance DAC and a less than optimal layout I'd say you should do something about it.
single-ended input? improper (not twisted, unshielded, shield not properly connected) input cables running too close to the inductor or high current traces? what DAC? layout (pics)?

also, how bad is it? how sensitive are the speakers, how audible is it (distance)?

PS: I took a look at the audiocircle NCORE builds thread and I simply can't understand why some go to extreme lengths with casework and such but at the same time use "audiophile" output wires left untwisted. somehow I was surprised to see that balanced inputs were used at all.
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Last edited by mr_push_pull; 27th November 2012 at 11:37 AM.
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Old 27th November 2012, 12:55 PM   #5677
Julf is offline Julf  Europe
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Originally Posted by mr_push_pull View Post
I simply can't understand why some go to extreme lengths with casework and such but at the same time use "audiophile" output wires left untwisted
Because audiophile magic voodoo beats science?
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Old 27th November 2012, 12:59 PM   #5678
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Originally Posted by Julf View Post
Because audiophile magic voodoo beats science?
Yupz, it does every time!! Sience is just an inconvenience Takes time and effort..
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Last edited by Mark.Clappers; 27th November 2012 at 01:01 PM.
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Old 27th November 2012, 01:15 PM   #5679
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Originally Posted by Julf View Post
Because audiophile magic voodoo beats science?
that would explain it, but still... properly twisting the wires would take 1 minute and not connecting them on opposing sides takes just as much effort as doing it.

anyway, I'm trying to get my head around something. there are enough reports about the NCORE being substantially better than the UCDs in the bass dept. this correlates with my personal experience, the UCDs sounding bass shy compared to a good class A amp. sometimes (with double bass for instance) I feel that a high-pass filter has been applied and lower tones are missing, thus making the instrument sound not exactly real.
what I'm unable to do is correlate this with the measured performance of said amps. anyone have any idea? even speculation would be better than nothing.

oh, and to robbbby: I searched your posts and looks like you have the Mytek 192 DAC and (according to you) it has a high (100-200 ohms) output impedance. that would explain your noise issues.
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Last edited by mr_push_pull; 27th November 2012 at 01:22 PM.
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Old 27th November 2012, 02:29 PM   #5680
OllBoll is offline OllBoll  Sweden
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Didn't Bruno describe that the NCore improvement over the UCD in the bass an illusion since it is the improved top end that makes the difference?

If I remember correctly he himself was not convinced that the NCore beats the UCD in the bass when used in an active system.
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