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 2nd July 2008, 02:37 AM   #21
diyAudio Member
 
mod_evil's Avatar
 
Join Date: Dec 2004
Location: Rio
Send a message via MSN to mod_evil
I found the SG505 schematic on Diyaudio.com and I'm thinking to build this.

Does anybody have a PCB for this?

Thanks for the help.

Best Regards,
Felipe
__________________
My blog!
www.felipenavarro.net
  Reply With Quote
Old 2nd July 2008, 11:52 AM   #22
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
The PCB which Cordell used for his Audio article can be found on page 11 of this PDF:

http://www.cordellaudio.com/instrume...d_analyzer.pdf

You can save yourself a lot of headache by purchasing a used Wavetek, Krohn-Hite Oscillator, using the chassis, power supply and putting in new switch assemblies. The power supply should be well insulated from the rest of the oscillator -- you can even use some PCB material or a cut up beverage can to prevent emi and rfi from migrating onto the oscillator PCB.
  Reply With Quote
Old 2nd July 2008, 01:13 PM   #23
diyAudio Member
 
mod_evil's Avatar
 
Join Date: Dec 2004
Location: Rio
Send a message via MSN to mod_evil
Dear jackinnj,

I live in Brazil, here haven't that Oscillators... The unique option which we can have here is some China Function Generators, and the Goods Functions Generators from HP and Tektronix is really expensive.

That PCB at the page 11 is the PCB of SG505? In the page 12 there is a schematic different of SG505.

Are you certain?

Best Regards,
Felipe Navarro
__________________
My blog!
www.felipenavarro.net
  Reply With Quote
Old 2nd July 2008, 01:38 PM   #24
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
The SG505 and the Cordell Oscillator use the same topology -- they are both state variable oscillators -- Bruce Hofer -- the inventor of the SG505 went on to co-found Audio Precision. Cordell credits Hofer at the end of the article on page 8 of the PDF. The paper is on the AES website "A Comparison of Low Frequency RC Oscillator Topologies" -- written when Hofer was at TEK.

The Cordell oscillator provides only a few number of frequencies, while the SG505 is continuously variable, but in reality, you don't need to check every little nook and cranny.
  Reply With Quote
Old 2nd July 2008, 02:03 PM   #25
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
If you really want low-tech solution for a low THD oscilator, then the lamp-stabilized wien-bridge is very good...especially if you use a low-wattage, high voltage lamp bulb such as a 240volt/3Watt .. these have very slow thermal reactance and will easely give you low THD...


Second hand is also very nice: I bought a Krohn-hite 4400 for ? 150$ off ebay.. wich give me <100dB THD...
  Reply With Quote
Old 2nd July 2008, 03:22 PM   #26
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Quote:
Originally posted by tschrama

Second hand is also very nice: I bought a Krohn-hite 4400 for ? 150$ off ebay.. wich give me <100dB THD...
You and Martin are the only guys who have purchased one of these.

There was another really, really good oscillator described in Audio Amateur a while back -- you use a CMOS clock (divide down with a crystal) and follow it with a pair of LTC1063 low pass oscillators. There is a tiny bit of clock-through which can be removed with a 2nd order active filter. I suppose that you could use other LP switched cap filters, I just happened to buy a bunch of the Linear chips off ebay a couple years back/
  Reply With Quote
Old 2nd July 2008, 11:12 PM   #27
diyAudio Member
 
mod_evil's Avatar
 
Join Date: Dec 2004
Location: Rio
Send a message via MSN to mod_evil
Friends,

When you need to use a Wien Bridge to generate a sinewave, YOU MUST HAVE A OPA602 or a OPA627.

The sinewave is WONDERFUL with these op-amps.

I'm generating 130khz with the OPA627 and 126,4khz with the OPA602. I will test other smaller cap value to see the hightest frequency which OPA627 can oscillate with the Wien Bridge.

The problem now is with the square wave.

When i'm using a OPA602, to top frequency which I have a clean sinewave was 7khz.

=/

Best Regards,
Felipe Navarro
__________________
My blog!
www.felipenavarro.net
  Reply With Quote
Old 3rd July 2008, 02:37 AM   #28
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
A square wave is the sum of all the odd harmonics of a sine wave. Most voltage feedback opamps run out of gain...
  Reply With Quote
Old 3rd July 2008, 03:37 AM   #29
diyAudio Member
 
mod_evil's Avatar
 
Join Date: Dec 2004
Location: Rio
Send a message via MSN to mod_evil
I will test a 4011 to generate the square from the sine.

Do you have any idea why I'm having problems with the period of the square wave, when it is bigger than 18khz, and when it's smaller than 400hz.

When the square wave is smaller than 300hz the top of the square have a angular problem.

See the photo which it attached here.

The frist photo is the lower problem. And the second photo is the problem with high frequencies.

This is a circuit using a operational in comparator mode. The negative input is connected to the sinewave output, and the positive input is conected to the ground.

Best Regards,
Felipe Navarro
Attached Images
File Type: jpg dsc05956 (large) (medium).jpg (32.7 KB, 322 views)
__________________
My blog!
www.felipenavarro.net
  Reply With Quote
Old 3rd July 2008, 03:38 AM   #30
diyAudio Member
 
mod_evil's Avatar
 
Join Date: Dec 2004
Location: Rio
Send a message via MSN to mod_evil
Another photo.

Another information. The suppy haven't a regulator.
Attached Images
File Type: jpg dsc05961 (large) (medium).jpg (43.0 KB, 317 views)
__________________
My blog!
www.felipenavarro.net
  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
I hate violin. tade Music 43 14th June 2007 04:26 PM
Don't you just hate it when Trout Tubes / Valves 49 31st May 2006 05:06 PM
Things you hate xplod1236 Everything Else 131 14th April 2006 02:27 PM
I hate you. Sch3mat1c Forum Problems 10 3rd February 2003 11:58 PM
I hate Veneer!!!! Milzie Multi-Way 38 21st December 2002 06:27 PM


New To Site? Need Help?

All times are GMT. The time now is 04:07 PM.


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