THD Analyzer finished w/ pics

[Val_r]

Hi,

I just wanted to share with the forum bros my last build, based on the project by Mr. Bob Cordell, that I wish to thank for his good attitude.
It can be found at:

http://www.cordellaudio.com/papers/build_a_thd_analyzer.shtml

This is a serious project for advanced DIY lovers! Yes, I really mean that, since you should REALLY love DIY'ing to get involved in this kind of project, be prepared to spend a LOT of hard working time before you can finally measure your machine THD.
Obviuosly I'm saying this because, loving DIYing, I decided to do it, but for more practical people out there, that will sure ask me: "Is it worth the pain?" , the answer is: go on the web and buy a good used piece of gear!
:grin:

Enjoy the pics.

 

[veermaster]

Amazing! Well, I know I would never dig into building this but I highly respect your beautiful work!

 

[radiance]

Yes sire! Serious DIY indeed...Man, this looks like a lot of work.

:thumb:

 

[barclaycon]

Complimenti !
That looks like like a lot of work. Well done.

 

[NewYorkDave]

Nice work!

I was into DIY test equipment myself a few years ago. It's quite a good feeling to be able to build, test and troubleshoot projects using equipment you also built yourself.

 

[Rossi]

Holy cow! :thumb: :thumb: :thumb:

I guess I better keep measuring/ballparking THD using a PC and software. This looks way out of my league. :shock:

 

[bcarso]

Congrats for having the stamina to finish it!

 

[JohnRoberts]

yup congrats... That Cordell design is pretty serious stuff. I recall reading it when it was originally in the magazines.

Some brute force but some very clever design work in there too. I liked the agc circuit he used in his low distortion sine wave generator.

JR

 

[Samuel Groner]

Excellent! :thumb:

Did you do the mods I suggested in the other thread? No hum problems with the torroid unshielded?

Samuel

 

[Val_r]

Hi guys,

Thank you all for your appreciations.

[quote author="bcarso"]Congrats for having the stamina to finish it![/quote]
Oh, you are absolutely right, a real stamina needed to build this...

[quote author="JohnRoberts"]yup congrats... That Cordell design is pretty serious stuff. I recall reading it when it was originally in the magazines.

Some brute force but some very clever design work in there too. I liked the agc circuit he used in his low distortion sine wave generator.

JR[/quote]
Yes, it works fine all the time.

[quote author="Samuel Groner"]Did you do the mods I suggested in the other thread? No hum problems with the torroid unshielded?[/quote]

Hi Samuel, didn't know about your mods, do you have a link to that thread?
Hum... no probs for all the frequencies, only in the 20Hz range I can see a bit of residual, but I will sure add a shield.
One prob I encountered:
HF oscillations, many hours spent to find the guilty one: it was IC33, an LM318 used as voltage follower in the product filter amp, problem solved by using a 0.1uF cap between pins 5 and 7, a compensation which reduces somewhat the settling time of the op amp.
Besides that, all went ok.

Respect,

Val.

:wink:

 

[Samuel Groner]

Didn't know about your mods, do you have a link to that thread?

I remembered wrong, I suggested the changes to another oscillator, but they equally apply to the Cordell design: www.groupdiy.com/index.php?topic=24311

Did you implement the fixed or variable filters?

Samuel

 

[tony dB]

Congrats and Massive Respect!!!

 

[Val_r]

[quote author="Samuel Groner"]
I remembered wrong, I suggested the changes to another oscillator, but they equally apply to the Cordell design: www.groupdiy.com/index.php?topic=24311

Did you implement the fixed or variable filters?[/quote]

Ah, I see. Interesting.

As you can see from the first picture, I have used the variable filter version.

Thanks again.

Respect,

Val.

:green:

 

[guavatone]

Wow .... cojones grandes!