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USB sound card for audio spectrum analysis
USB sound card for audio spectrum analysis
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Old 24th April 2016, 01:23 AM   #171
vicnic is offline vicnic  Latvia
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Join Date: Oct 2004
Location: Riga
Wish to tell you little about one amazing result with the E-MU 0202. Not far ago got this card from the ebay auction for 30 EUR. I was planning this for my laptop as spectrum measurement tool. This USB sound card uses AK5385 as ADC. The chip is semi compatible with the AK5394, and I thought, that maybe I can replace the ADC chip, if it needed, but seems that is not needed. After one working day, some changes in the buffer amp and little tricks I got wonderful results from the right channel of the ADC. The left channel was more worse (seems that the chip internal problems), and I blocked it. As result I got this relatively small "magic" box, and the nice spectrum picture:
http://content32-foto.inbox.lv/album...02/0202out.jpg
http://content32-foto.inbox.lv/album...2/1kHz0202.jpg
http://content32-foto.inbox.lv/album...02/0202ins.jpg

Victor.
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Old 24th April 2016, 05:21 AM   #172
altor is offline altor  Israel
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Victor, what was the signal in dBFS?
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Old 24th April 2016, 06:07 AM   #173
Frex is offline Frex  France
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Hello,

The spectrum seem to have fundamental level at 0dBFS, but it need to be confirmed.
I'm very surprised by this results, THD is less than -130dB here and even AK5394 doesn't reach this ! Maybe you fell on the best one
I have a ESI juli@ that have same ADC as E-MU202 (AK5385), and i would be interested to know what mods you have done ?
And also, i'm curious but what is the FFT software do you use ?
Regards.

Frex
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Old 24th April 2016, 07:54 AM   #174
mkc is offline mkc  Denmark
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USB sound card for audio spectrum analysis
Hi Victor,

Looks good. Could you be persuaded to go into a bit more detail about your modifications? Perhaps detailed enough so it could be replicated?

Mogens
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Old 24th April 2016, 10:30 AM   #175
altor is offline altor  Israel
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Quote:
Originally Posted by Frex View Post
Hello,

The spectrum seem to have fundamental level at 0dBFS, but it need to be confirmed.
I'm very surprised by this results, THD is less than -130dB here and even AK5394 doesn't reach this !
I see -135dB noise floor.
Don;t know about 5385 in this soundcard, but with 5394 it can be expected ~ -150dBFS, so this picture can have 0dB=-15dBFS.

@-15dBFS signal, 5394 have harmonic level ~ -140dBFS (see attachment. @44.1 the results are better).
Attached Images
File Type: png onyx_192_1k15db.png (30.8 KB, 912 views)
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Old 24th April 2016, 12:04 PM   #176
vicnic is offline vicnic  Latvia
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Join Date: Oct 2004
Location: Riga
Hi,
Yes, Alex. You are almost right. 0dB=-16dBFs in my picture. All the soundcards, that I previously had, required offset for the best results in the spectrum measurement. My main internal soundcard Asus Xonar D2 works with -23dB offset...
I am using Spectrum Lab ver. 2.4.0.31. Sampling rate was 192/24 with maximum averaging.
Mainly all changes was done around ADC buffers. High gain and noisy input amps was disconnected. Later, I shall post more detailed information - when I get it in suitable format.

Regards,
Victor.
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Old 24th April 2016, 12:10 PM   #177
euro21 is offline euro21  Hungary
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Join Date: Sep 2004
Location: Budapest
USB sound card for audio spectrum analysis
Hi Victor,

Do you know this topic?
http://www.diyaudio.com/forums/equip...ml#post4175441

EMU USB soundcards is super devices, but its PCB design is not optimal, so need to some modifications (left channel power line redirection).

For years ago I use 0404USB for measuring (Audiotester, Visual Analyser). I use it below -10dB
because over it distortion of input device is growing.
Attached Images
File Type: jpg Victors 1k right.jpg (66.2 KB, 867 views)
File Type: jpg Victors 1k left.jpg (72.3 KB, 853 views)
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Old 24th April 2016, 12:13 PM   #178
mkc is offline mkc  Denmark
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USB sound card for audio spectrum analysis
Hi Victor,

Thanks, always interesting to see how much performance these boxes can be hot-rodded to deliver.

Looking forward to see your modifications.

Mogens
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Old 24th April 2016, 01:41 PM   #179
vicnic is offline vicnic  Latvia
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Join Date: Oct 2004
Location: Riga
Quote:
Originally Posted by euro21 View Post
Hi Victor,

Do you know this topic?
http://www.diyaudio.com/forums/equip...ml#post4175441

EMU USB soundcards is super devices, but its PCB design is not optimal, so need to some modifications (left channel power line redirection).

For years ago I use 0404USB for measuring (Audiotester, Visual Analyser). I use it below -10dB
because over it distortion of input device is growing.
Hi,
Yes, I heard about this problem in the E-MU 0404. The schematic around the input buffers seems very similar, but the PCB topology probably may be different.
I observed small level spikes in my E-MU 0202 left channel also without the signal, and I could not remove these spikes even if I short circuit the ADC chip left channel inputs. Similar, but lower spikes also was induced to the right channel, before I drastically blocked the left. It was blocked with the big DC offset - one input almost to +5V, other input to GND.

Regards,
Victor.
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Old 24th April 2016, 03:38 PM   #180
HpW is offline HpW
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Join Date: Mar 2002
Quote:
Originally Posted by vicnic View Post
I was planning this for my laptop as spectrum measurement tool. Victor.
Here some measurements using your lovely LDO's...

And it will always be the hard part with the input LNA & best ADC. And finally for a DIY, to effort such HW/SW or even to build with the existing knowledge such HW.

Hp
Attached Images
File Type: png LDO Victor 1kHz - 10kHz-1.png (16.5 KB, 846 views)
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Last edited by HpW; 24th April 2016 at 03:41 PM.
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