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Old 11th December 2011, 12:10 PM   #18941
SY is offline SY  United States
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It does help to read an entire post, rather than stopping after the first sentence. Of course, comprehension of what's written helps as well.
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Old 11th December 2011, 12:19 PM   #18942
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Quote:
Originally Posted by SY View Post
It does help to read an entire post, rather than stopping after the first sentence. Of course, comprehension of what's written helps as well.
Okay, here are entire posts:
Quote:
Originally Posted by Joshua_G View Post
Possibly one is dBv while the second is dB.
Quote:
Originally Posted by SY View Post
dB referenced to what? There's a 60dB (1000x) difference in the reported numbers.

The issue is noise referenced to input vs noise referenced to output.
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Originally Posted by Joshua_G View Post
Atkinson should be asked.
Quote:
Originally Posted by SY View Post
You don't need to, all you have to do is read the article. It's quite clear.
Quote:
Originally Posted by Joshua_G View Post
So why did you ask?
Quote:
Originally Posted by SY View Post
I didn't. I was clarifying some gibberish. That has to happen every now and then in threads like this which alternate between performance and performance art.
Anyhow, comprehension of what's written may improve SNR of the threads here.
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Old 11th December 2011, 12:19 PM   #18943
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Quote:
Originally Posted by scott wurcer View Post
I disagree, eliminating current noise completely is unrealistic.
No reason not to do both. A popular magazine has an interesting quandary- it could measure en and in vs frequency and report that. With this information, any reader with a basic engineering background can calculate the noise that he'll get from a particular cartridge. The problem is that the audience is dentists, investment bankers, and lawyers, who in general wouldn't know what to make of that info.

If it were my magazine, I'd report the shorted input, but then repeat the same measurement with a standard source (say, 400R + 0.5H or something) representing a MM and/or 5R representing a MC. Then show the standard source data compared to an ideal noiseless preamp with the same gain and frequency response curves on the same graph so that the reader can see what the preamp is actually adding, compared to theoretical limits determined by the source. These are easy measurements to do with the sort of setup that Stereophile has and give a readily understandable and graphically dramatic indication of what the real world noise of the preamp is likely to be.
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Old 11th December 2011, 12:22 PM   #18944
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John,

Quote:
Originally Posted by john curl View Post
It's not true, Thorsten.
My concern is with DC current through the coils of the cartridge. If we want to keep this to a minimum with MM Bipolars are out. You can allow a little more with MC, but even here you really have to watch it.

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Originally Posted by john curl View Post
IF you keep the betas high and the Iq low, the problem is minimized.
Why not use a J-Fet? 2SK246 will do fine for MM only...

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Originally Posted by john curl View Post
THEN, if you use a lowish inductance cartridge like a Grado, or a SOTA Shure MM cartridge, the inductance is not so high.
I do not consider any MM to be "Sota", though some can be charming.

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Originally Posted by john curl View Post
Third, the INTEGRATION due to the RIAA curve removes the slight increase in current noise that might be generated with frequency.
Sorry John, but it does not, when compared to a pure resistor.

There is always a rise in noise (self noise and if bipolar's are used a rise in current derived noise) compared to resistor...

Honestly, I would NOT use Bipolar Op-Amp's (or bipolar transistors) in a position where they couple into a MM Cartridge (or a volume control at that) while there is still a low capacitance J-Fet or Mosfet in some garage foundaries sortiment...

But to each their own.

Ciao T
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Old 11th December 2011, 12:47 PM   #18945
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...
If it were my magazine, ...
...
If it were your magazine, would you do only measurements, or would you include also listening impressions?
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Old 11th December 2011, 12:54 PM   #18946
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I'd do what it takes to sell magazines and ads. John has done superbly well in that regard.
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Old 11th December 2011, 01:00 PM   #18947
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Pavel,

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Originally Posted by PMA View Post
The proper definition of S/N I am attaching now.
The definition is for power, which is meaningless in the context of line level electronics though technically correct.

This is a nice attempt at muddying crystal clear waters, as this stages precisely the same as stating the signal amplitude in dB with reference to a known reference level and the noise amplitude in dB with reference to a known reference level, as in -145dBV noise and -66dBV signal.

So what you post underlines precisely why we specify noise we do, as the signal level is essentially unknown and may vary widely with cartridge (from 0.1mV for some of the lowest out MC Cartridges to nearly 10mV for some higher output MM types)...

Quote:
Originally Posted by PMA View Post
I also can make you sure that I know what is a dBV (re input). But is rarely used for the system with 1mV operating range (input).
Well, I'm afraid I disagree on usage. In fact, input noise is VERY commonly used to specify noise in circuits with variable gain and low signal levels, precisely because of the difficulties to come up with any other sensible specification.

See for example the following links. As they are pro-audio related the measurements are stated as Ein in dBu rathe rthan dBV, which will give a touch under 3dB difference...

Measuring Mic-Preamp Noise | Benchmark Media

http://www.avisoft.com/test/noisefloors.pdf

Selecting Mic Preamps

Rupert Neve Designs Microphone Impedance and Noise

APHEX Systems 1100 Class A Tube Mic Preamp +A/D Conv.

All of these use input referred noise (Ein) in dBu for specifying noise, so not only is this kind of specification regular, but in fact common (lest you wish to imply that the folks at Aphex, Benchmark, Rupert Neve, Rane and others all do not know what they are doing).

Ciao T
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Old 11th December 2011, 01:01 PM   #18948
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John has done superbly well in that regard.
Yes. The best, IMO.
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Old 11th December 2011, 01:03 PM   #18949
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It's not a matter of opinion- it's numbers ($$$).
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Old 11th December 2011, 01:12 PM   #18950
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It's not a matter of opinion- it's numbers ($$$).
Yes. In chosing medium-to-high-level technical content and no ads for Linear Audio I am condemned to breaking even at best.
I could never make a living from it.
Then again, nobody tells me what to publish and what not. A great luxury!

jan
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