Low-distortion Audio-range Oscillator - Page 160 - 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 24th January 2013, 06:26 PM   #1591
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 1audio View Post
No schematic. Have not found a source. Perhaps we should buy a manual or two.

The FFT requirements are simple since it converts everything to 420 Hz or so, so even the tenth harmonic is only 4 KHz. You could even use an ipod-iphone spectrum analyzer app.
I'd buy one if I could find one (manual). BTW -- here is the patent number for the ShibaSoku distortion analyzer: USA ---4,417,310 Nov.22, 1983.
  Reply With Quote
Old 24th January 2013, 06:33 PM   #1592
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Dick: I have a 4400 and 4402. They have a procedure for adjusting the oscillator (I think Demian sent me the manual) -- to get to this level it's almost mandatory to work on a weekend morning, use as short a cable as possible, and let it warm up for a half-hour or so without changing the frequency. You can watch the THD tick down as it relaxes. If you muck up with the frequency and controls it will still oscillate below 0.001% One of these had a bad power supply regulator and was pretty inexpensive.
  Reply With Quote
Old 24th January 2013, 07:01 PM   #1593
1audio is offline 1audio  United States
diyAudio Member
 
Join Date: Mar 2004
Location: SF Bay Area
Blog Entries: 3
Dialing in a 4400 is easy with the Shibasoku. Simply adjust for minimum 2nd. Its almost cheating. They are very good, much better than the specs. I have not explored opamp tweaks. With the Shibasoku generators I just don't feel the need.

I have modified the KH4400 for injection locking. It helps when doing the really high res stuff since the generator has enough drift and phase noise to limit measurements. Here are measurements of my KH4400 using the AKM5394A (and 16M point fft) (locked to my Boonton)

I saw a cheap KH4400 on ebay a few days ago. I don't think there are customers for them at the usual $500+ price range.
Attached Images
File Type: jpg KH4400 locked to Boonton 16M.JPG (129.3 KB, 286 views)
File Type: jpg KH4400 locked to Boonton 16M 10 KHz.JPG (134.7 KB, 267 views)
__________________
Demian Martin
Product Design Services
  Reply With Quote
Old 25th January 2013, 05:26 PM   #1594
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 1audio View Post
I have modified the KH4400 for injection locking. It helps when doing the really high res stuff since the generator has enough drift and phase noise to limit measurements. Here are measurements of my KH4400 using the AKM5394A (and 16M point fft) (locked to my Boonton)

.
From what i've read, -120 is about it for stock used oscillators. A few new ones are better and the old one's can get improved. Below that -120 is possible with a bit of work.... but it looks like you then get into parts selection -- contacts, caps, pots et al. perhaps even changing the C & R in the twin-T for lower noise values. Those parts have to be the best and a lot of trial and error to find them. Eventually, the noise of R's etc get in the way. Fortunately, for audio amps IMO under -100 (.001) under load is quit good and nothing to be ashamed of. Thx-RNMarsh

Last edited by RNMarsh; 25th January 2013 at 05:30 PM.
  Reply With Quote
Old 28th January 2013, 08:37 AM   #1595
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Interesting situation here --- Two oscillators - the 339A and Victors -- show very low on ShibaSoku.... verified Victors oscillator distortion spec. BUT, the FFT from the new unit QA400 shows both at -100-ish (<1.0 v rms). Now what the heck? -RNM
  Reply With Quote
Old 28th January 2013, 09:23 AM   #1596
dimitri is offline dimitri  United States
diyAudio Member
 
dimitri's Avatar
 
Join Date: Oct 2002
Location: retired
Send a message via ICQ to dimitri
Richard, you posted 339A measurements in #1580. Can you please mention data for Victor's oscillator? Can you put a load for Victor's oscillator, say 600 Ohm?
  Reply With Quote
Old 28th January 2013, 11:36 AM   #1597
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
Quote:
Originally Posted by RNMarsh View Post
Interesting situation here --- Two oscillators - the 339A and Victors -- show very low on ShibaSoku.... verified Victors oscillator distortion spec. BUT, the FFT from the new unit QA400 shows both at -100-ish (<1.0 v rms). Now what the heck? -RNM
Weird, can somebody borrows you an AP?
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 28th January 2013, 02:08 PM   #1598
davada is offline davada  Canada
diyAudio Member
 
Join Date: Jul 2004
Location: Fort St John, BC Canada
Quote:
Originally Posted by RNMarsh View Post
Interesting situation here --- Two oscillators - the 339A and Victors -- show very low on ShibaSoku.... verified Victors oscillator distortion spec. BUT, the FFT from the new unit QA400 shows both at -100-ish (<1.0 v rms). Now what the heck? -RNM

Hi Rick,

Are you using a notch filter to suppress fundamental? If not then you are measuring the qa400 distortion.

I had the same trouble measuring Victor's oscillator. Reads high on the QA400.

On the other hand is the Shibasoku distortion unit calibrated?
You can test this by injecting known levels at harmonics of and along with a fundamental.
Use two 600 ohm oscillators in series or parallel. Set fundamental to 1Vrms and vary the harmonic level at different frequencies.

You can do the same for the QA400. Remember you have to do the math for any THD readouts on either but individual harmonics should be fine.
The injected harmonic(s) must be well above oscillator distortion to be meaningful.

Be aware that all windowing of FFT produces ripple in the pass band to some degree. Flat top is the only one that doesn't but the noise is higher.
Read the help file.
__________________
David.

Last edited by davada; 28th January 2013 at 02:26 PM.
  Reply With Quote
Old 28th January 2013, 05:20 PM   #1599
HpW is offline HpW  Switzerland
diyAudio Member
 
Join Date: Mar 2002
Location: Switzerland (Bern)
Well,

Quote:
Originally Posted by davada View Post
H
Be aware that all windowing of FFT produces ripple in the pass band to some degree. Flat top is the only one that doesn't but the noise is higher.
Read the help file.
It really depends of the used FFT Window... there are low and higher order functions even on the Flat top...

What really surprises (on the given spectrum) the repeated inter-modulation, more or less, over the full measured bandwidth. Interesting would also to zoom on the fundamental to have to phase noise..

HpW
__________________
www.hpw-works.com
  Reply With Quote
Old 28th January 2013, 06:08 PM   #1600
1audio is offline 1audio  United States
diyAudio Member
 
Join Date: Mar 2004
Location: SF Bay Area
Blog Entries: 3
Quote:
Originally Posted by RNMarsh View Post
Interesting situation here --- Two oscillators - the 339A and Victors -- show very low on ShibaSoku.... verified Victors oscillator distortion spec. BUT, the FFT from the new unit QA400 shows both at -100-ish (<1.0 v rms). Now what the heck? -RNM
You are bumping into the Crystal ADC's limits.

I have attached a plot of the same generator as above (KH4400) measured with the QA400. You can see the difference in the distortion floor. Other key tricks, you must get the frequency to be precise or the bins will miss. That's why I added the injection lock to the KH4400. Make sure the internal generator matches the frequency since that is what their software uses to determine the harmonics.

The QA400 software is a good start and will get useful results immedately. However if something like HPW-works were to support the hardware I would find that very helpful (hint!).
Attached Images
File Type: jpg QA400.jpg (179.3 KB, 174 views)
__________________
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 11:46 AM
ultra-low distortion audio oscillator geekysuavo Analog Line Level 16 26th March 2013 04:04 PM
Low distortion oscillator? rjm Equipment & Tools 30 4th May 2011 11:45 PM
Can we improve this low distortion sine oscillator ? gaetan8888 Solid State 22 29th March 2009 01:30 PM
Simple, low distortion 1kHz oscillator jackinnj Solid State 4 6th October 2003 04:58 AM


New To Site? Need Help?

All times are GMT. The time now is 05:17 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