My implementation of the Cordell Distortion Analyser - Page 3 - diyAudio
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Old 2nd November 2009, 02:53 PM   #21
Jaac is offline Jaac  Netherlands
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Looks realy nice !

Where did you get those switches ?

And how did you implement the balanced part ? doesn't that add distortion ?
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Old 2nd November 2009, 03:16 PM   #22
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A 24 bit 192kHz sound card will allow measurements up to half that frequency 88kHz), and the 24 bit resolution also means the noise floor of the system is well below -120dB, which is quieter than most electronics you will ever make.

We bought a used M-Audio card for 100 euro and Audio tester software for another 50 euros - works a treat!

Regards, Allen (vacuum State)
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Old 2nd November 2009, 05:54 PM   #23
EUVL is offline EUVL  Europe
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> Where did you get those switches ?

Just stack multiple normal 3-stack ones to make them up, with some specially made mechanical parts to extend the shafts.

> And how did you implement the balanced part ? doesn't that add distortion ?

The output is just an inverting amp with an IC-buffer (HA5002) in the feedback loop. The input part is another opamp configured as differential amp. Using one of these LM4xxx opamps, there is hardly any additional distortion that you can measure.

Yes, I am sure there are many solutions for distortion measurement, not the least Audio Precision gear. But that is not the point of this thread.


Patrick
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Old 3rd November 2009, 08:04 AM   #24
Jaac is offline Jaac  Netherlands
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I forgot to type the next question; what kinda battery do you use and how long could you operate the analyzer with it ?
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Old 3rd November 2009, 12:38 PM   #25
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Quote:
Originally Posted by EUVL View Post
> Where did you get those switches ?

Just stack multiple normal 3-stack ones to make them up, with some specially made mechanical parts to extend the shafts.

> And how did you implement the balanced part ? doesn't that add distortion ?

The output is just an inverting amp with an IC-buffer (HA5002) in the feedback loop. The input part is another opamp configured as differential amp. Using one of these LM4xxx opamps, there is hardly any additional distortion that you can measure.

Yes, I am sure there are many solutions for distortion measurement, not the least Audio Precision gear. But that is not the point of this thread.


Patrick
The Harris IC's were in a Krohn-Hite analyzer I owned at one time -- it was single frequency, 1kHz.

Not to gild the lily too much, but the THAT Corp line drivers measure better than those from ADI.
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Old 3rd November 2009, 08:12 PM   #26
EUVL is offline EUVL  Europe
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Just ordinary alkaline. Never used up one set as yet. I don't measure for hours.

Patrick
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Old 4th December 2009, 08:33 AM   #27
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Stupendous achievement Patrick, really well done!
Are a couple of months I'm thinking of building it.
I have already ordered the rotary switch, but are still undecided whether to use relays.
You had thought?
I realize the high number of relays necessary but this could, for example, allow a kind
of automatism in the tests. Of course, driving the relays with a digital logic.

Giuliano
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Old 4th December 2009, 04:15 PM   #28
EUVL is offline EUVL  Europe
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Switch is very simple to use.

If you want to do automated testing, you might as well go for complete software control and use some 24 bit sound cards as mentioned in post #22.
He did not have the fun though.....




Patrick
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Old 4th December 2009, 05:13 PM   #29
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Hi,
I prefer the stand-alone instruments, are more pratical.
Screen with the copper board you used, it's necessary or as a preventive precaution?

Giuliano
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Old 4th December 2009, 05:45 PM   #30
EUVL is offline EUVL  Europe
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I had some boards with outdated photo-resist. So rather than throwing them away, I used them as shields.

Patrick
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