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

Equipment & Tools From test equipment to hand tools

EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
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 6th March 2016, 05:52 PM   #11
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
Hello,

You are right Chris, PPS needs some care when soldering.
I've not tried COG on the design, but i will do it maybe if i have the time.
From what i've read, PPS and NPO /COG are both very linear (very low THD contribution).

I've done today some others measurements on the oscillator, but with my notch filter,
slightly modified to have better depth at it's frequency.
The output level is set to 0dBm (710mVrms).

Spectrum with notch filter before ADC :

Click the image to open in full size.


Frex
  Reply With Quote
Old 7th March 2016, 07:25 AM   #12
Samuel Groner is offline Samuel Groner  Switzerland
diyAudio Member
 
Join Date: Jun 2005
Location: Zürich
Quote:
Originally Posted by Frex View Post
It's a good idea, would you be ok if I send you a bare PCB to build it and make some tests? (I will of course send it for free). I need to keep the finished unit to investigate and tried some others things.
Thanks very much for your offer! At the moment it is hard for me to find any spare time, and I want to set my priorities on my own oscillator design. So building a unit myself is not feasible. But of course I would return your unit ASAP (shouldn't take more than a few days)--just let me know in case!

Samuel
__________________
www.nanovolt.ch
  Reply With Quote
Old 7th March 2016, 07:06 PM   #13
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
Ok i understand.
I want to make some extended tests on a second unit to compare them together.
So i prefer to wait the end of this month and then i will send you
an unit to perform some test with your equipements.

Regards.

Frex
  Reply With Quote
Old 13th March 2016, 11:15 AM   #14
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
Arrow EOSC10KV3 performance measurements

Hello all,

These days i worked on the oscillator in two ways ;
1 / Wiring a second circuit board using NPO/COG capacitors instead of PPS.
2 / Improving my notch filter box to show more easily spurious below 120dB.

The notch filter box has been modified to add 40dB (x101) gain of the signal at the notch output.
Even with this 40dB gain, the level at the output is enough low to not produce significant THD in the ADC
(Level is about -18dBV, near to be the lowest THD point of ADC).
To verify this, i use a passive divider instead of the notch to check Gain block at same signal level.
The schematics of the notch filter box look like this :

Click the image to open in full size.

You can also show below some pictures of the box, and how it is connected to ADC input (EADCAKMV1).

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

You can show the shielded (French chocolate) box that avoid spurious noise coming from anywhere.

Click the image to open in full size.


The good news is that effectively the NPO capacitors seem to be superior,
i can get lower harmonics level than with PPS type.

First you can show the check spectrum where no significant harmonics are visible.
(Here the oscillator signal through the divider without notch filter)

Click the image to open in full size.


You must note that the showed spectrum must be translated to -40dB down to give the real level
because of the 40dB gain of the notch box output.

We can see that without the notch filter, the amplifier output noise is very low with all spurious
below 160dBV (-120-40 = -160dBV).
So, we can resolve very low harmonics level with this amplifier, without introducing significant THD.
(Because we will get same level at the ADC input when we fit the notch in signal path).


Now, in the graph below we show the notch filter response (with the 40dB gain) and the oscillator signal.
We verify then that the attenuation of the notch at the oscillator frequency is equal to the attenuation
we have previously tested the signal chain to ensure no THD is introduced by the ADC at this signal level.
The attenuation is -58dB +40dB gain = -18dBV level at ADC input
==> This is well the signal level we have tested previously.

Click the image to open in full size.


Finally, we can show the measurement result of the new EOSC10KV3 oscillator using NPO/COG capacitors.
The last graph show the notch filter/gain box Bode plot (violet) and the amplified output of the notch
filter.

Click the image to open in full size.


As we see, all harmonics level are extremely low, below -140dBc (H2) !
The calculated THD using these harmonics levels is about -136.5dB or 0.000015 %

Samuel, i will prepare a unit for send you this week for testing with your high-end setup.
I'll send you PM about that soon.



Frex
  Reply With Quote
Old 14th March 2016, 03:28 AM   #15
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Q: Have you looked at the phase response of the notch at 2H to be sure the angle isnt subtracting from the true 2H level ??

THx-RNMarsh
  Reply With Quote
Old 14th March 2016, 04:30 PM   #16
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
Hello Richard,

Why do you think phase shift of the notch filter will change the H2 level ?
I think that FFT show harmonics level regardless of the phase. No ?
(except if others THD products occur after the notch and are in opposite phase...).

Frex
  Reply With Quote
Old 15th March 2016, 06:43 PM   #17
akhi9980 is offline akhi9980  India
diyAudio Member
 
Join Date: May 2013
Smile Ultra Low distortion oscillator

Hi Frex,

Can you post Gerber for same? I want to build the same for 1KHz oscillator.

With Regards,
AKHILESH K
  Reply With Quote
Old 15th March 2016, 08:17 PM   #18
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
Hello Akhilesh,

First, the oscillator has not been designed to work at 1kHz, so changing frequency could be much work than you expect (I will work soon on the 1kHz version but not ready yet).
I don't provide the Gerber files, but you can buy the bare PCB from me, see first post.
With the bare PCB i provide a very complete design folder to build the oscillator.
Regards.

Frex
  Reply With Quote
Old 16th March 2016, 06:34 AM   #19
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by Frex View Post
Hello Richard,

Why do you think phase shift of the notch filter will change the H2 level ?
I think that FFT show harmonics level regardless of the phase. No ?
(except if others THD products occur after the notch and are in opposite phase...).

Frex
Only because I have seen the notch affect the 2H level with other analyzers and notch filters.

You might change the notch Q and or depth to see if there is any 2H level change. usually, the affects are not an issue on 3H and beyond.

THx-RNMarsh
  Reply With Quote
Old 16th March 2016, 08:40 PM   #20
Frex is offline Frex  France
diyAudio Member
 
Join Date: Nov 2009
EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !
Ok Richard.
I've done many measurements and i am very confident about their validity.
But of course, when we speak about some hundreds of nanovolts, we must take much care when interpreting ...
So, i have finished my first oscillators with it's enclosure (updated pictures on my first post).
and i am nearly ready to send the unit to Samuel.
I think he could make some serious measurements with it's high-end setup that i can only dream....

Frex
  Reply With Quote

Reply


EOSC10Kv3 - LT AN67 10kHz oscillator : new updated version !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
LT AN67 Ultralow THD 10kHz sine oscillator group buy. Frex Group Buys 63 6th March 2016 08:36 AM
AN67 Ultra-low THD 10kHz sine oscillator PCB iko Swap Meet 6 25th September 2010 06:43 AM
UPDATED!!! It blew the fuses! <cries!> Rarkov Solid State 7 6th November 2002 09:12 AM


New To Site? Need Help?

All times are GMT. The time now is 10:03 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki