John Curl's Blowtorch preamplifier part II

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Anyone ever seen true 32 bits without errors, skip codes, glitches and uncorrelated spuriae? Real worls is somewhere at 20 bits, if excellent.
PMA, this 32 bits is not sampling rate, 24 bits is large enough. It is precision for calculation. Then rounded for 24 bits with dithering.
Anyway, i do not know so much AD converters in 32 bits, and i worry what kind of previous analog stage able to use all the bits, indeed :)
 
For the reasons you have just described, I built a measuring amplifier with gain 40dB to be able to measure noise level of preamplifiers and make FFT analysis (noise level which is normally below common audio measuring system threshold) and to be able to measure at low output level. My SW computes unweighted integral noise in 20Hz - 20kHz band, so no tricky "noise bottom" like -150dB etc, which depends on bin width (number of samples in FFT, sampling frequency and possibly averaging as well). Noise of the measuring amp is attached. So I amplify the preamp output by 40dB, measure noise and ten subtract -40dB to get preamp's noise. I also measure distortion, at about 10 - 20mVrms of preamp output voltage. I have not measured any increase of harmonic distortion at low signal output level, but found differeces in noise of preamplifiers and its spectra.

With this method, I can measure noise level down to -126dB/ref 1Vrms (20Hz - 20kHz, unweighted). The best preamp I measured had noise -115dB/1Vrms unweighted, 20Hz - 20kHz. The gain of that preamp was 14dB.


I have to admit I am still in the dark with what exactly you are measuring. In particular the lack of 1/f noise (increasing by 10dB/decade with decreasing frequency) is intriguing.

What are the units on the Y axis? dB ref. 2V of what? It's certainly not the standard nV/rtHz. Could you draw the noise of a 1Kohm resistor on the same graph?
 
diyAudio Member RIP
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What's often interesting about datasheets is what is left out. After that, what the conditions of measurement and specification are.

I miss the characteristic curves in the old databooks for various transistor "processes". But I'd conjecture that people were referring to them and holding the manufacturer to them, rather than the guaranteed specifications for a particular part selected from that process.
 
I use an abacus. None of these newfangled calculational methods.

Just the other day, I was having lunch with some of my colleagues, and we were talking at a level that people here wouldn't understand. There were questions about wire and bead materials and how they can impact the accuracy of accounting. But if you're happy with wood and steel, more power to you. We selected jade and nichrome after extensive testing, but that's the difference between a Bentley and a Yugo. Works for me!


:D
 
diyAudio Member RIP
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Sy,
Don't we just daisy chain a bunch of 8086 chip until we get to 64 bits.........:D
I knew one guy who pointed proudly to a shunt JFET switch and resistor divider at the input to a box with a bunch of signal processing, that commenced thereafter with an ADC, and asserted that with this he had added an extra bit of resolution!

Later he left that company and at another, was proud of specifying a wirewound resistor for its parasitic inductance.

I don't know where he is today --- possibly designing electronics for lithium battery packs?:eek:
 
Why, but why so much people are afraid with digital ? Or believe in some evil inside ?

Comparing TV emitters size and power (analog VS digital) , looking at the number of channels you can get on the same home antenna, and the quality of HD images+surround sound, who will never dream to return back to NTSC ?

Todays personal cameras are hundred times better than all the most expensive analog professional gear ever produced. For 1/1000 the price and the size !!!!
And the same, of course, apply to the audio world.
 
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I use an abacus. None of these newfangled calculational methods.

Just the other day, I was having lunch with some of my colleagues, and we were talking at a level that people here wouldn't understand. There were questions about wire and bead materials and how they can impact the accuracy of accounting. But if you're happy with wood and steel, more power to you. We selected jade and nichrome after extensive testing, but that's the difference between a Bentley and a Yugo. Works for me!
:D

You really crack me up :)
 
Just the other day, I was having lunch with some of my colleagues, and we were talking at a level that people here wouldn't understand. There were questions about wire and bead materials and how they can impact the accuracy of accounting. But if you're happy with wood and steel, more power to you. We selected jade and nichrome after extensive testing, but that's the difference between a Bentley and a Yugo. Works for me!

Who originally wrote this post? :D
 
I was just on a phone call with the CEO of a major car company talking about the problems they're having with their crankshafts. We've been working as competitors since 1964, when I showed them that they were doing their transmissions all wrong. This is the sort of thing my colleagues do between lunches at expensive restaurants. We discussed the fact that no one can tell Coke from Pepsi as well. Have you ever worked in a Pepsi factory? I certainly have!

:D
 
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