DIY Distortion Analyzer/Analysis?

[Speedskater]

The Cordell THD Analyzer

The "Audio" magazine article (July, Aug, Sept 1981) is 30 pages long, of which 9 pages are schematics !

The project uses 40 IC's and 5 multi-pole, multi-section rotary switches !

One is a 5 position, 9 section 18 pole switch.

 

[mlloyd1]

Someone posted them at one time, but was warned about copyright infringement. Mr. Cordell requested the schematics not be posted.

A local college MIGHT be a place to see if microfilm of the back issues (and therefore copies) are available that way.

Check earlier in this thread. I posted the address of the company that provided PCBs for this project a LONG time ago.
mlloyd1

 

[vbd]

Cordell analyzer
I checked the previous posts, and the schematics were not posted, as the copyright problem arose...
Unfortunately, the Audio magazine is not well known here, in France...
I'm contemplating the schematics published in Electronics World August 1999 by Ian Hickmann, that would make a much simpler analyzer, with a smart topology, at first glance...
Any thoughts about it ?

 

[jackinnj]

Audio Mag - 1981

ok, you asked for it: http://www.tech-diy.com/thd_analyzers.htm

 

[Pjotr]

Re: THD, IMD, S/N testing software

You might want to check-out

http://www.purebits.com

Sample Champion software is their main product

It has several plug-ins available,
one of which deals with Audio Quality.

(SNR, THD, THD+N, and IMD)

Other plug-ins available deal with -

Room Acoustics
Impedance (Thiele-Small parameters)
Filter Banks and more

Purebits is really good software but it cost some money. I am quite happy with it.

Also check out:

http://www.sumuller.de/audiotester/
http://www.audiotester.de/mainE.htm

For $28 it is really a bargain. With a 96 kHz soundcard you can do almost any distortion analyses needed for DIY.

 

[sam9]

bad link

The tech-diy.com link posted by jackinnj has gone bad. Too bad, the image looked good.

 

[Kay]

http://www.dazyweblabs.com/shannonsoft/page3.html

Try this for measure, it's free

best regards
Kay

 

[cocolino]

originally posted by sam9 The tech-diy.com link posted by jackinnj has gone bad. Too bad, the image looked good.

Try it again later - if it does not work anymore and when You have a big mailbox - email me - I saved the hole article already

By the way building this Analyzer looks like hell of a project.
I think it`s much less hassle to buy a used Tek AA501/SG505 combo or a HP339 at ebay and at the end this might be even cheaper.

 

[jackinnj]

My apologies

I moved the folder on the website. It'll be fixed in the morning.

Jack

 

[jackinnj]

File is PDF'd

it's saved as a PDF (actually 3 PDF's) at the following location:
http://208.55.153.67/thd_analyzers.htm

 

[sam9]

Thanks.

Thanks for your efforts. I had wondered where such a project might be hidden. Now for some heavy reading.

 

[vbd]

Thanks a lot, jackinnj for your time !!!
This classical hard wired approach looks interesting !!!
Cheers !!!!

 

[tortello]

Thanks Jackinnj,
very interesting stuff!
Marcello

 

[AuroraB]

2 questions ...

1. Having studied the analyzer article quite extensively over the last months, - I wonder if it is possible to further improve upon it, by careful component selection, new opamps etc... the ref. .0003% is quite impressive for a DIY design, but still.......any ideas..??

2. Have any of you tried the programs referred to, like the Sumuller audiotester??
results anyone...

 

[jackinnj]

to get even lower

if it really has to go a lot lower, you can consider using very low noise op-amps (let me know if you need AD797's !) and hand matching the filter network resistors, more careful attention to power supply noise, more shielding -- there has been a really great series of articles in Electronics World by Bateman in which he crafted a 1kHz distortion analyzer capable of reading the wrinkles on a gnat's eyebrow.

if you go to the Analog Devices website and noodle around their application notes dealing with ultrasound, sonobuoys etc. you will pick up some valuable hints.

 

[john curl]

Folks, you are pushing your luck. Do you have the time and money to build a first class distortion analyzer? Why not try to get a pretty good one on e-bay or somewhere else and modify it, if necessary? Trust me, it will save you both time and money, to get something that already is in a box, ground loops worked out, and has a good meter. If you look around, (and are lucky) you can get a good distortion measuring instrument for 5%-10% of new cost. The used equipment companies seem to charge very high prices for the same thing that you can find elsewhere. Just look around.

 

[Nelson Pass]

All true, but this is diyAudio.com

 

[cocolino]

All true, but this is diyAudio.com

Indeed, and exactly therefore I buy equipment second hand -
because after building my own DIY distortion-analyzer, DIY power-supplies, DIY spectrum-analyzer, DIY noise-meter, DIY curve-tracer, DIY scope (no joke, I have done this already.....well, it was a kit.... but still), DIY LCR-Meter... .......I would need a second life for my actual audio projects and....... meanwhile I`m aware that I got only one

 

[Michael Rothacher]

Don't forget one of NP's favorite Sagan quotes:

'To make an apple pie, you must first create the universe'

 

[sam9]

Oscillator to match ?

Of course to get the most from a distortion analyzer you need a sine wave source with lower distortion and noise than the analyzer. Most diy sine generators come up a little short comparred to what people have been talking about in these post.

This leads me to the question: Has anyone tried to build the sine wave generator in the LT1115 datasheet?

If so, can you explain how it works -- it is just too many opamps "running in circles" for me to grasp clearly (or even murkily).