Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

How do I measure - 140 dB noise levels?
How do I measure - 140 dB noise levels?
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 25th September 2008, 09:03 PM   #1
gentlevoice is offline gentlevoice  Denmark
diyAudio Member
 
Join Date: Oct 2007
Location: Denmark
How do I measure - 140 dB noise levels?
Default How do I measure - 140 dB noise levels?

Hello,

I'm looking for a cheap and straightforward way of measuring noise levels down to about -140 dBs (ref. 2 VDC). Any of you who knows how this can be done? A soundcard would be prefered but I haven't seen any with this kind of specs at a reasonable price .....

Regards,

Jesper
  Reply With Quote
Old 25th September 2008, 09:33 PM   #2
richie00boy is offline richie00boy  United Kingdom
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
How do I measure - 140 dB noise levels?
-140dB is the realm of high quality test equipment, i.e. not reasonable price.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
  Reply With Quote
Old 25th September 2008, 09:47 PM   #3
wakibaki is offline wakibaki  United Kingdom
Banned
 
Join Date: Jan 2008
Default Re: How do I measure - 140 dB noise levels?

Quote:
Originally posted by gentlevoice
-140 dBs (ref. 2 VDC)
You mean 200nV? Ultra low noise opamp ~2.5nV/ Hz^-2 so you're going to see this much noise in the circuit with a bandwidth of 6400Hz already.

Or somebody correct my numbers...

w
  Reply With Quote
Old 26th September 2008, 03:21 AM   #4
ostripper is offline ostripper  United States
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Smoky Mountains , Tennessee
I think Nelson Pass "Passlabs" is/was working on a ultra low
noise precision amp to allow for testing sub 110DB noise.
Do a search in "passlabs" you might find it.

My soundcard (M-audio/envy 24) is -122 at 20khz -126 at 1khz
I use FFT and can see this, but it is good enough.(can see
junction noise in transistors... yikes)

BTW .. Why??? -110-120 noise is spectacular ,if it is below that
why the fuss?
OS
  Reply With Quote
Old 20th October 2008, 04:26 PM   #5
gentlevoice is offline gentlevoice  Denmark
diyAudio Member
 
Join Date: Oct 2007
Location: Denmark
How do I measure - 140 dB noise levels?
Hi again,

- and thanks for your replies - they made me think further into what my needs are.

I would like to measure very, very low noise levels, e.g. the noise of batteries, however, would need to do so also at very low frequencies, i.e. down to <1 Hz. At the same time I will be measuring noise (at a high resolution) up to ~ 100 kHz.

I guess this could be done using a very low noise amplifier feeding into a quality (192 kHz/24 bit) soundcard, possibly with the exception of the ability to measure down to 1 Hz (I haven't seen any capable of measuring at these frequencies..?). The soundcard needs to be able to connect to my PC via USB or firewire. Also it should be able to record and playback at the same time as I intend to use it with the Praxis software (http://www.libinst.com/).

@ Ostripper: BTW I did a search on Nelson Pass' ultra low noise amp but did not find anything ... nor on M-audio/Envy ... ??

Suggestions are appreciated ...

Best regards,

Jesper
  Reply With Quote
Old 20th October 2008, 04:28 PM   #6
kristleifur is offline kristleifur  Iceland
diyAudio Member
 
Join Date: Apr 2006
Location: Reykjavík
This one may work, I'm not sure:

Tangentsoft LNMP (Low Noise Measurement Preamp)
http://tangentsoft.net/elec/lnmp/
  Reply With Quote
Old 20th October 2008, 06:18 PM   #7
gentlevoice is offline gentlevoice  Denmark
diyAudio Member
 
Join Date: Oct 2007
Location: Denmark
How do I measure - 140 dB noise levels?
@kristleifur

Thanks - it would be an interesting design for me, however, I don't have a source for the AD797 - which by the way seems to be very low noise...

Do you know where to source it?

Regards,

Jesper
  Reply With Quote
Old 20th October 2008, 07:48 PM   #8
tschrama is offline tschrama  Netherlands
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
maybe this is an option.. with some mods for the low freq ability.. less then 0.6nV/sqrtHz.. gives 60nV at 10KHz bandwidth, or -150dB ref 2V

http://www.diyaudio.com/forums/showt...hreadid=129961
  Reply With Quote
Old 20th October 2008, 07:55 PM   #9
kristleifur is offline kristleifur  Iceland
diyAudio Member
 
Join Date: Apr 2006
Location: Reykjavík
Quote:
Originally posted by gentlevoice
Thanks - it would be an interesting design for me, however, I don't have a source for the AD797 - which by the way seems to be very low noise...

Do you know where to source it?
Sorry, don't know, but you may want to check with Tangent himself, and at the Headwize.com DIY headphone amp forums. I think they were discussing these amps there a while ago.
  Reply With Quote
Old 20th October 2008, 11:42 PM   #10
cuibono is offline cuibono  United States
diyAudio Member
 
cuibono's Avatar
 
Join Date: May 2006
Location: City of Angles
The Emu 0404 usb and Asus Xonar D2 have very very low noise and distortion levels...
  Reply With Quote

Reply


How do I measure - 140 dB noise levels?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Can I use a scope to measure powerline noise? Saurav Equipment & Tools 31 5th January 2017 04:32 AM
Speakers popping and static noise at all volume levels PPI Amp duderino201 Car Audio 21 8th May 2010 09:19 PM
Lowest noise levels difi Chip Amps 3 3rd March 2004 10:42 PM
Noise levels in NiMh batteries? A 8 Digital Source 2 27th July 2003 04:47 PM


New To Site? Need Help?

All times are GMT. The time now is 12:35 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki