DIY Analog-to-Digital Converter project.Audio measurements tool - Page 5 - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

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 29th March 2010, 04:00 PM   #41
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
The output of the Super Oscillator is a bit high for the HP3577, so an attenuator is necessary. The display is that of the bleed through from the DA4084 notch filter.

Perhaps you've seen this chart -- comparing the AP Generator with a KH-4400:

Click the image to open in full size.
  Reply With Quote
Old 29th March 2010, 07:22 PM   #42
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
Arrow oscillator.

Hello,

jackinnj, below how looks my version of the LT oscillator.

Ghg, i'm not sure that active notch filter allow to improve measurement resolution of THD.
I have built one, using two AD797, and finally, it seem to add THD...
Fully passive notch filter is also poor, impedance is too high and it's low Q factor give high attenuation at harmonics frequency.


Left, the new AA5381 ADC working, at right the oscillator and it's differential outputs.
Click the image to open in full size.

Inside the oscillator...
Click the image to open in full size.

Left, my previous ADC (with AKM5394).At center the new AA5381 and at
right the oscillator again.
Click the image to open in full size.


Frex.
  Reply With Quote
Old 29th March 2010, 08:13 PM   #43
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Very nice work. I tried an aluminum enclosure for my Super-Oscillator, but it would pick up the 60Hz! That's why it's in a steel container. I had to tweak the cap values to get it spot-on for 10kHz.
  Reply With Quote
Old 29th March 2010, 08:57 PM   #44
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
Arrow results.

Hello,

Thank jackinnj, yours is also nice !
I have noticed that the DC source of the oscillator must be quiet for very low HD. Bad line rejection issue could add intermodulation around Fosc.
To solve it, very good PSU or battery powering is required.
Using metal housing is not a problem if is it connected to ground (of oscillator).Metal case improve line and EMI rejection.
I use for mine with a JSR06 low noise PSU.

Now, all my measurements results on the AA5381 ADC, and some others with my older ADC to compare.
Hello,
Attached Files
File Type: pdf AA5381_noisefloor_48kHz_0dBFS.pdf (103.4 KB, 323 views)
File Type: pdf AA5381_noisefloor_96kHz_0dBFS.pdf (102.3 KB, 110 views)
File Type: pdf AA5381_noisefloor_192kHz_0dBFS.pdf (190.5 KB, 173 views)
File Type: pdf AA5381_10kHzTHD_96kHz_4Vpp_se.pdf (137.2 KB, 143 views)
File Type: pdf AA5381_10kHzTHD_96kHz_4Vpp_diff.pdf (131.7 KB, 102 views)
File Type: pdf AA5381_10kHzTHD_192kHz_4Vpp_diff.pdf (136.4 KB, 162 views)
File Type: pdf EADCAKM_noisefloor_48kHz_0dBFS.pdf (102.8 KB, 116 views)
File Type: pdf EADCAKM_noisefloor_192kHz_0dBFS.pdf (102.3 KB, 109 views)
File Type: pdf EADCAKM_10kHzTHD_192kHz_4Vpp_diff.pdf (135.8 KB, 205 views)
  Reply With Quote
Old 30th March 2010, 10:43 AM   #45
ghg is offline ghg  Austria
diyAudio Member
 
ghg's Avatar
 
Join Date: Apr 2002
Location: Vienna
You both did a fine job on these 10kHz super oscillators, I am jealous ...
Any boards left, you layout kings ???

>frex: Ghg, i'm not sure that active notch filter allow to improve measurement
>resolution of THD.I have built one, using two AD797, and finally, it seem to add THD...

Well, the AD797 is a beast, I never managed to get it 100% stable on the breadboard and was too lazy for doing a good pcb layout,
but just take an AD712 and all is fine. Take a look at the plot below, a standard active twin T dual opamp twin T, gives 60dB attenuation,
THD is at the same level as the related "sweet spot" FFT of the TI eval board.
A standard soundcard without this notch would be worse by 20dB.

>Fully passive notch filter is also poor, impedance is too high and it's low Q factor >give high attenuation at harmonics frequency.

Works too, use just a +20dB FET buffer and take the insertion loss in account.
Attached Images
File Type: png Act. Twin-T.png (38.7 KB, 2305 views)
__________________
I hate "sounding amps", except these are Marshalls, driven by Eric C. or Jeff B., period.
  Reply With Quote
Old 30th March 2010, 12:43 PM   #46
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
Quote:
Originally Posted by ghg View Post
Works too, use just a +20dB FET buffer and take the insertion loss in account.
Gary, do you mean a fet input opamp based +20dB buffer after the notch filter? The buffer/amp would also have to be very low thd+n, no? I'm planning to build a notch filter myself so I'm interested in what you built.
  Reply With Quote
Old 30th March 2010, 01:30 PM   #47
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Quote:
Originally Posted by ghg View Post
You both did a fine job on these 10kHz super oscillators, I am jealous ...
Any boards left, you layout kings ???
One of the guys at big semi bought all the boards I had made -- I don't know if they ever got them working!

Same thing happened when I built the phase-meter from an Intersil Application Note -- the semi companies will sell their development modules for a fraction of the engineering time and money which goes into them in the hopes of selling tens of thousands of parts.

AD797 seems to like a copper plane underneath it -- if you don't want to lay out a PCB consider "dead bug" style development. Development boards are OK, but really fall down in low noise circuits as they pick up all kinds of radiated energy. With the AD797, it's important as well to read the entire datasheet!

Last edited by jackinnj; 30th March 2010 at 01:38 PM.
  Reply With Quote
Old 30th March 2010, 04:39 PM   #48
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
ghg,

The PCB of my oscillator is not professional. It's home made.
If you are interested, i can send you Gerber files to build it.
(you can read/print it with any Gerber reader like GCprevue or others).
(Maybe if enough DIYers are also interested, it could be a good idea to get professional PCB from PCBcart or others ? )

For the notch filter, i will try to work on it this week with others OPAMPs.
Like says ikoflexer , could you post or send your schematic of notch filter ?

Frex
  Reply With Quote
Old 30th March 2010, 05:13 PM   #49
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
Before seeing this discussion I was thinking of building the attached. Not exactly with that opamp... but something like that. Haven't thought about the 20dB buffer/amp yet.
Attached Images
File Type: png filter-notch-1b.png (22.4 KB, 1038 views)
File Type: png filter-notch-1b-plot.png (11.9 KB, 909 views)
  Reply With Quote
Old 30th March 2010, 10:57 PM   #50
ghg is offline ghg  Austria
diyAudio Member
 
ghg's Avatar
 
Join Date: Apr 2002
Location: Vienna
TWIN T notch filter

1. passive + 20dB amp:

EDN -- 11.10.94 Oscillator keeps THD below 1 ppm Fig. 2

2. active:
Distortion Analyser Fig. 4


@frex: Gerber would be fine, thanks a lot.

@ikoflexer:
>Gary, do you mean a fet input opamp based +20dB buffer after the notchfilter? The buffer/amp would also have to be very low thd+n, no?
Imagine 0dBV to the notch, after the notch you will get app. -60dBV.
Todays opamps show about/or less than -100db THD ( 0dBV input,1kHz,+20dB gain ).
At an input of -60dBV we have app. -160dB opamp selfdistortion.
__________________
I hate "sounding amps", except these are Marshalls, driven by Eric C. or Jeff B., period.
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
need an analog-to-digital converter schematic prorms Digital Source 0 28th March 2008 09:29 PM
Digital to Analog Converter DAC With Cable mg16 Swap Meet 1 11th September 2006 07:27 AM
Analog to Digital converter amirmk Digital Source 9 26th November 2005 01:50 PM
Differences between Digital and Analog Audio oscarcasalini Digital Source 1 8th January 2004 12:32 AM
Digital to Analog converter condor655 Digital Source 4 15th May 2003 11:02 PM


New To Site? Need Help?

All times are GMT. The time now is 07:08 AM.


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