Low-distortion Audio-range Oscillator - Page 219 - 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 12th April 2013, 06:16 AM   #2181
1audio is offline 1audio  United States
diyAudio Member
 
Join Date: Mar 2004
Location: SF Bay Area
Blog Entries: 3
First, how I added injection locking to the KH4400. Its a junk box Radio Shack transformer (1:1) and two 100K resistors and a cap. I used a transformer to get ground isolation. It did not really work. I need to find a shielded transformer.

Then the QA400 during measurements runs the generator in bursts. This does not work well with injection locking.

Fortunately the Boonton 1120 can be set very precisely (6 digits) and is locked to a TXCO. (I get value from the toy. . . )

I locked the KH4400 to the Boonton set to the frequency of the QA400 internal generator. You can see how the skirts narrow when the generator is locked. You will also see the third harmonic increase when locked.
Attached Images
File Type: jpg KH4400 locking.jpg (419.2 KB, 153 views)
File Type: png KH4400 locked.png (22.8 KB, 149 views)
File Type: png KH4400 free run.png (23.3 KB, 146 views)
File Type: png KH4400 locked to 1120.png (29.4 KB, 137 views)
__________________
Demian Martin
Product Design Services
  Reply With Quote
Old 12th April 2013, 06:34 AM   #2182
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by scott wurcer View Post
Dick, the comparison was aluminum with fins, anodization, and all the other good stuff. the copper was just a lump. I keep pointing out there is nothing to learn unless ALL the factors are covered.
Scott, one thing to check is whether your buddy actually allowed for enough time to reach equilibrium. Until that point, his block of copper may well look better, but possibly after equilibrium, the alu-with-fins might do better.
The copper may rise slower in temp, but end up at a higher final temp.

jan
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!

Last edited by jan.didden; 12th April 2013 at 06:37 AM.
  Reply With Quote
Old 12th April 2013, 12:33 PM   #2183
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Demian -- that is really neat!
  Reply With Quote
Old 12th April 2013, 12:35 PM   #2184
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Scott

The other issues are that the e of tarnished copper is quite high. As mentioned copper conducts heat much better so all of the surface area will be at the same t. And of course the method used to measure the t. A probe with putty is accurate an ir sensor can give silly readings. That brings up the issue of the anodizing. Black is the color you see. There are different methods to get to black. The cheapest way is with a dye. Cheaper dyes are not as black at ir as the better ones from sources such as Sandoz.

I thought the distortion reduction in injection locking were clear. If you do a high level of 10% that is 20 db. Even a square wave has only 1/3 sin (3x) or another -10 ish. Add the minimum two pole filtering of the tuning elements for another 18 on the 3rd.

Now 10% is a high injection level. But you are starting with a clean sine wave. In actual practice they of course don't exist. Also for most folks locking at 1% injection from the output of a digital frequency divider has low enough distortion, there is no reason to go any cleaner.

Now using a D-A with smarts behind it opens entirely new methods of not just locking it but also opens up all the other control issues. Not just loop gain and matching harmonic cancelation, but also some neat sampling based cancelation or correction techniques.

ES
  Reply With Quote
Old 12th April 2013, 02:04 PM   #2185
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by simon7000 View Post
Scott

The other issues are that the e of tarnished copper is quite high. As mentioned copper conducts heat much better so all of the surface area will be at the same t. And of course the method used to measure the t. A probe with putty is accurate an ir sensor can give silly readings. That brings up the issue of the anodizing. Black is the color you see. There are different methods to get to black. The cheapest way is with a dye. Cheaper dyes are not as black at ir as the better ones from sources such as Sandoz.

I thought the distortion reduction in injection locking were clear. If you do a high level of 10% that is 20 db. Even a square wave has only 1/3 sin (3x) or another -10 ish. Add the minimum two pole filtering of the tuning elements for another 18 on the 3rd.

Now 10% is a high injection level. But you are starting with a clean sine wave. In actual practice they of course don't exist. Also for most folks locking at 1% injection from the output of a digital frequency divider has low enough distortion, there is no reason to go any cleaner.

Now using a D-A with smarts behind it opens entirely new methods of not just locking it but also opens up all the other control issues. Not just loop gain and matching harmonic cancelation, but also some neat sampling based cancelation or correction techniques.

ES
Ed I thought you said to avoid a pure sine wave? That's what made no sense. It turns out this system seems to act like an ultra high Q amplifier which is perfect. This will reject the injectors harmonics by a huge amount. I think you misunderstand I am pulling the frequency by 10% the amplitude is tiny.

Also I have to apologize a little on the heatsink stuff. I have been fighting this for years. The JEDEC specs for ThetaJA are very pessimistic because the don't include things that would apper in a normal application like conduction out the leads. Parts are to be measured soldered to small dots on tiny boards.

Does it make sense to thermally isolate a heatsink and mount it upside down to defeat natural convection to prove the point that radiation can be up to 20% of the loss? (number from IBM) Bolted to the chassis and free and clear to encourage natural convection we are down to a few percent at best difference. BTW turning off radiation all the way in that program will give a wrong answer anyway, raw aluminum extrusion is .2-.3 emissivity.
__________________
Silence is so accurate.

Last edited by scott wurcer; 12th April 2013 at 02:08 PM.
  Reply With Quote
Old 12th April 2013, 02:05 PM   #2186
davada is offline davada  Canada
diyAudio Member
 
Join Date: Jul 2004
Location: Fort St John, BC Canada
Quote:
Originally Posted by RNMarsh View Post
FYI -- Attachment 342057

So there you are. Clear now? Good.

[Physicsforums.com/archive/index.php/t-131758.html]
That's why copper bottoms are put on cooking pots. Nothing new here.
__________________
David.
  Reply With Quote
Old 12th April 2013, 02:19 PM   #2187
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Scott,

I thought you misread that. Using a simulation with a clean sine wave is misleading because that is not how it was normally done.

I though you were injecting 10% because of component tolerances. 1% is typical. A pull range of 10% is wide, normal is +3/-2 or so. I have done most of this with Wein bridges.

As you know the e part of the heatsink depends on operating temperature. For an exposed heatsink 45C is often the limit to prevent injury. Inside a case you might see 80C with modern power transistors. Allowable die temperatures are 50C higher than when I started designing stuff. So the e ratio really depends on how hot you can take it. BTY 10% is what I would consider starting to be significant.

On a cost basis it is about $.03 per square inch for quality anodizing in small quantities. A .1" x 1" x 1" piece of aluminum costs just about the same. Makes the economics interesting.

ES
  Reply With Quote
Old 12th April 2013, 02:25 PM   #2188
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Demian

Ever try two transformers in series? (Load R between them.)

ES
  Reply With Quote
Old 12th April 2013, 04:03 PM   #2189
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by jan.didden View Post
Scott, one thing to check is whether your buddy actually allowed for enough time to reach equilibrium. Until that point, his block of copper may well look better, but possibly after equilibrium, the alu-with-fins might do better.
The copper may rise slower in temp, but end up at a higher final temp.

jan
That was the first suggestion from the gathered elites.
__________________
Silence is so accurate.
  Reply With Quote
Old 12th April 2013, 04:33 PM   #2190
1audio is offline 1audio  United States
diyAudio Member
 
Join Date: Mar 2004
Location: SF Bay Area
Blog Entries: 3
Quote:
Originally Posted by simon7000 View Post
Demian

Ever try two transformers in series? (Load R between them.)

ES
Good idea. I'll need to check the junk box. I can ground the intermediate connections to reduce the noise coupling.
__________________
Demian Martin
Product Design Services
  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
Radford Low Distortion Oscillator Series 2 audiomik Equipment & Tools 21 19th February 2014 10:46 AM
ultra-low distortion audio oscillator geekysuavo Analog Line Level 16 26th March 2013 03:04 PM
Low distortion oscillator? rjm Equipment & Tools 30 4th May 2011 10:45 PM
Can we improve this low distortion sine oscillator ? gaetan8888 Solid State 22 29th March 2009 12:30 PM
Simple, low distortion 1kHz oscillator jackinnj Solid State 4 6th October 2003 03:58 AM


New To Site? Need Help?

All times are GMT. The time now is 07:49 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