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Old 29th December 2010, 10:05 PM   #11
jcx is online now jcx  United States
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RMAA has useful free version

Audacity open source sound editor lets you play/record

Ltspice can generate complex test .wav, and import the recorded response for analysis with its fft and .meas

SciLab is a free MatLab workalike for more complex signal processing of the .wav data

I've used all of the above freeware with the Juli@

another interesting looking sw is Audio DiffMaker for null testing/residual difference meas with time alignment, FR correction

Last edited by jcx; 29th December 2010 at 10:11 PM.
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Old 30th December 2010, 02:38 AM   #12
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Quote:
Originally Posted by panomaniac View Post
I dunno. Here is a quick look at my computer soundcard playing a 1KHz tone.
Pico set to 156Khz limit, zoomed in. 1M termination (the scope).

It does allow you to see noise and other stuff pretty low.
Looks very good for 12bit. I'm just curious, why they name their DAC 12bit-16bit. THD also looks much better than I would expect from 12 bit.
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Old 30th December 2010, 03:44 AM   #13
Pano is offline Pano  United States
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Beats me.

It's not mine, I just borrow it from time to time. I do find it very handy.
Some of their stuff goes much higher, but is only 8 bit. 10Mhz is plenty for most audio use. For Class-D higher could be better, but even this one helps.
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Old 30th December 2010, 05:18 AM   #14
BV is online now BV  Slovakia
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I am using for THD an IMD measurements Lynx L22 card and ARTA software (free)
Some results with loopback
Attached Images
File Type: png IMD.png (11.0 KB, 334 views)
File Type: png THD1k.png (11.5 KB, 338 views)
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Old 30th December 2010, 05:42 AM   #15
Frex is offline Frex  France
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begemot61 ,

Hello,
Of my own experience, the AKM AD/DA converters are really excellent. If you find a sound card that use the AK5394A ADC you will get one of the better ADC system with very low THD specs.
TI or Cirrus IC aren't better, only maybe the ESS sabre ADC(ES9102), but not many infos are available on this IC and they are locked...
About your needs, i think too that sound card like juli@ or others is very good starting point for low budget(less than 150$).
If you have more, Pico-scope is good too, but not exactly same instruments.
Wider bandwidth, lower resolution. It's depend on what you want to do with.
I personnaly use the digitial I/O of Juli@ sound-card (supporting 24/192l SR), with my DIY external ADCs. It's more easy to use than analog I/O of sound card (BNC inputs,+/-10V FS,DC coupled,..).
You can see more about this here.

I recommend you to absolutely avoid USB sound card for 192kHz operation.
This high sampling rate require high USB bandwidth that even USB2 don't work fine.
And of course, USB2 ask high processor resources.
For an external ADC/DAC, prefer Firewire you will avoid many problems.

About analysis software, two are very very good;
Spectraplus (not free, a 30 days free trial can be downloaded)
Oscillometerz (not free, shareware version fully working but stop analysis after 15s)
Many others FFT software exist, but i don't have find better than this.



Regards.


Frex

(Note; if i'm not wrong i think that ADC use in Lynx L22 of previous post is AK5394 from AKM !)

Last edited by Frex; 30th December 2010 at 05:44 AM.
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Old 30th December 2010, 05:46 PM   #16
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Quote:
Originally Posted by Frex View Post
begemot61 ,

Hello,
Of my own experience, the AKM AD/DA converters are really excellent. If you find a sound card that use the AK5394A ADC you will get one of the better ADC system with very low THD specs.
TI or Cirrus IC aren't better, only maybe the ESS sabre ADC(ES9102), but not many infos are available on this IC and they are locked...
About your needs, i think too that sound card like juli@ or others is very good starting point for low budget(less than 150$).
If you have more, Pico-scope is good too, but not exactly same instruments.
Wider bandwidth, lower resolution. It's depend on what you want to do with.
I personnaly use the digitial I/O of Juli@ sound-card (supporting 24/192l SR), with my DIY external ADCs. It's more easy to use than analog I/O of sound card (BNC inputs,+/-10V FS,DC coupled,..).
You can see more about this here.

I recommend you to absolutely avoid USB sound card for 192kHz operation.
This high sampling rate require high USB bandwidth that even USB2 don't work fine.
And of course, USB2 ask high processor resources.
For an external ADC/DAC, prefer Firewire you will avoid many problems.

About analysis software, two are very very good;
Spectraplus (not free, a 30 days free trial can be downloaded)
Oscillometerz (not free, shareware version fully working but stop analysis after 15s)
Many others FFT software exist, but i don't have find better than this.

Regards.

Frex

(Note; if i'm not wrong i think that ADC use in Lynx L22 of previous post is AK5394 from AKM !)
Thank you.
Lynx card showed really excellent results. But it is not in my preferred price range. Juli@ sound-card is probably the best option for me with very good performance.
Speaking about usb, is it so bad for modern multi-core PC? This is not really mastering application. Usb2 works OK while transferring big data arrays for external HDD. Is latency so important for THD measurements? Or I'll get glitchy data that the software would not be able to properly process?
What if I will not use it for duplex mode and use external test signal generator.

Probably, the most convenient way for measuring system is to use SPDIF in/out and build external AD/DA with some buffers and attenuators. This is not very complicated and some sort of additional front end would be convenient for any sound card. Are there any options for just SPDIF board or USB-SPDIF, that support 24/192?
Regards,
Eugene
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Old 31st December 2010, 12:12 AM   #17
mt490 is offline mt490  Australia
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Quote:
Originally Posted by BV View Post
ARTA software (free)
As far as free packages go I like ARTA as well, it's a bit better featured than RMAA.
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Old 31st December 2010, 07:42 AM   #18
Frex is offline Frex  France
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Hello begemot61,

Yes, a juil@ sound card is the more cost effective solution, and these AD/DA converters are very good.
About USB link, if you use high sampling rate, even with powerful computer you risk to get discontinuous audio data that is problematic for FFT processing.
Of course, it is worse with full-duplex mode....
With external HDD you can achieve high data rate, and fall of data rate is not a problem. Contrariwise, with external USB sound card, if at any time the data rate fall below what it need, you will have loss of data!
These problem is not a concern with internal PCi card or with firewire interface.
But, of course you can try it at your own risk.

Note too that if you use external generator instead of sound card DAC out(full duplex mode), you will not easily do some measurements that allow full-duplex mode, like Bode plot (frequency response)...

And last, you're right. Using SPDIF I/O of sound card (juli@!) with external A/D unit is the best solution. It's that i do.
Did you have read about my AA5381external ADC project ?



Frex.
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Old 31st December 2010, 06:32 PM   #19
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Hi Frex,
Yes, I looked at you ADC project. I was not able to download schematic (for some reason it was forbidden ) but it is clear what it is. I'm thinking in the same direction. And you right, it is not completely clear what you will get, until you build it and test. I was thinking about more complicated front end, some built in attenuators, but other than this it is very similar to yours.
I also liked your evaluation of LT AN67 generator. You results look good, but I'm thinking of the structure that is more like old Bob Cordell's generator. It has some reserves left, while using modern components. And I'm thinking of different amplitude stabilization method as soon as I don't need fast amplitude setting (not going to do F sweep, just a couple of fixed frequencies). This may allow to redo amplitude diagram, and, may be, get better THD and noise. Not finalized my thoughts and have not done any simulations yet.

Happy New Year!

Thanks,
Eugene
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Old 1st January 2011, 08:58 AM   #20
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Default Picoscopes

Just a further word on Picoscope, their 4000 series scopes are up to 16-Bit and that gets me down another order or so and quite sufficient for DIY work. So as not to seem biased, there are similar products from The Netherlands called Handyscope, by Tie-Pie Engineering which offers this resolution and possibly higher now.

However, the software capabilities of the PCB card scopes are really tempting because they offer so many graphical variations which are commonly posted here. Agree about how good Juli@ cards are but there are some other well shielded cards of 24/192 capability now, even in the big-name-brand domestic market. To realise anything approaching 24 bit you need a really good interface/ attennuator with cards. This little extra can cost unless you DIY as per some excellent threads here. Pete Millet's recent creation comes to mind as the ultimate.
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