John Curl's Blowtorch preamplifier part II - Page 3417 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th February 2013, 05:27 PM   #34161
diyAudio Member
 
Join Date: Nov 2011
Quote:
Originally Posted by Esperado View Post
OPA with offset.
Care to show it how it will work?

Quote:
Originally Posted by Esperado
With 32 bits, you can attenuate by 60db without any audible artifacts. What the hell ?
Indeed ..

http://www.jamminpower.com/PDF/48-bit Audio.pdf
  Reply With Quote
Old 4th February 2013, 05:36 PM   #34162
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Anyone ever seen true 32 bits without errors, skip codes, glitches and uncorrelated spuriae? Real worls is somewhere at 20 bits, if excellent.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 4th February 2013, 05:37 PM   #34163
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by elektroj View Post
Care to show it how it will work?
Nothing complicated: Applying a +2.5V *low noise* reference to the + input of the OPA (gain 1) , while you enter your signal to the -input.
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein
  Reply With Quote
Old 4th February 2013, 05:39 PM   #34164
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
.... yes, low swing (<5Vpp)
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 4th February 2013, 05:44 PM   #34165
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by PMA View Post
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 :-)
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein
  Reply With Quote
Old 4th February 2013, 05:48 PM   #34166
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
If 32 bit calculation is problematic, your computer won't work.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 4th February 2013, 05:54 PM   #34167
Waly is offline Waly  United Kingdom
diyAudio Member
 
Waly's Avatar
 
Join Date: Jan 2011
Location: London
Quote:
Originally Posted by PMA View Post
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?
  Reply With Quote
Old 4th February 2013, 06:00 PM   #34168
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
Sy,
Don't we just daisy chain a bunch of 8086 chip until we get to 64 bits.........
  Reply With Quote
Old 4th February 2013, 06:13 PM   #34169
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
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.
  Reply With Quote
Old 4th February 2013, 06:14 PM   #34170
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
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!


__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 01:02 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2