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P3 Adjustment for the average Hobbyist
P3 Adjustment for the average Hobbyist
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Old 20th July 2018, 01:17 AM   #111
wintermute is offline wintermute  Australia
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P3 Adjustment for the average Hobbyist
Yes the 2i2 is a proper sound card which is connected via USB. But performs the same basic functions as a PCI or pcie sound card. The main advantage of going with USB is that it is portable and can be used with a laptop.

There are some things I prefer about using a pci card (I find the gain knobs on the 2i2 really finicky to adjust), but the portability and being able to use a laptop running off battery are the main reasons I went with a 2i2.

edit: the main advantage of using a laptop (apart from portability) is that you can completely eliminate the PC as a source of ground loops.

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Last edited by wintermute; 20th July 2018 at 01:22 AM. Reason: add ground loop comment.
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Old 20th July 2018, 03:39 AM   #112
Russellc is offline Russellc  United States
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P3 Adjustment for the average Hobbyist
Quote:
Originally Posted by wintermute View Post
Yes the 2i2 is a proper sound card which is connected via USB. But performs the same basic functions as a PCI or pcie sound card. The main advantage of going with USB is that it is portable and can be used with a laptop.

There are some things I prefer about using a pci card (I find the gain knobs on the 2i2 really finicky to adjust), but the portability and being able to use a laptop running off battery are the main reasons I went with a 2i2.

edit: the main advantage of using a laptop (apart from portability) is that you can completely eliminate the PC as a source of ground loops.

Tony.
Thanks, I am beginning to understand more and more about this setup!

Russellc
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Old 20th July 2018, 08:51 PM   #113
MEPER is offline MEPER  Denmark
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I had my first play with 2i2 and ARTA software. A loop back test with a 1k sine. Fs = 48k and FFT = 131072. It looks very clean. No 2nd and 3rd harmonic which of course is good for a test sine generator. But it looks a little to good to be true?
If I turn up the signal so the green ring goes red......then I got a lot of distortion…..as expected.


What is a good value for FFT?
The number is the resolution? …..higher number better?
The recording takes longer if FFT is high.....which probably is logic.
There is a steep learning curve……...….
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Old 20th July 2018, 10:39 PM   #114
silasmellor is offline silasmellor  Denmark
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P3 Adjustment for the average Hobbyist
Hmm to me it looks like your noise floor is quite high at -80'ish. Maybe lower preamp gain and turn up your output dial. Did you use smoothing? Here is a loopback from my Mbox3 for comparison. Master volume all the way up (as i think Wintermute mentioned) and preamp around 10-11 o'clock.

P3 Adjustment for the average Hobbyist-ts-loopback-out1-in2-png


That's the lowest distortion i could get. Using balanced cables made no difference, and disconnecting the sleeve from the jack (or corresponding pin on XLR) actually gave me increased distortion.


You should be able to go lower for FFT length, 16 or 8k. I don't think it is a critical parameter, just makes measurements faster (with lower values).
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Last edited by silasmellor; 20th July 2018 at 10:42 PM.
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Old 20th July 2018, 11:11 PM   #115
MEPER is offline MEPER  Denmark
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Ok.....I tried again by setting the sine generator to -6 dB and set monitor to max. and then input gain to approx. 11 o'clock. But what did the real trick was to change Wnd from Uniform to Hanning. Avg set to linear. I have 0 dB at top and noise floor is now close to -130 dB. Now it looks more realistic with some 2nd and 3rd harmonic. One should think that output of sine generator will give best result if set to 0 dB for max. resolution in the DAC?
Will play more with that…….
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Old 21st July 2018, 01:38 AM   #116
Russellc is offline Russellc  United States
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P3 Adjustment for the average Hobbyist
Glad to see you getting somewhere with your setup! What was your device under test? A BA3 FE?

Russellc
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Old 21st July 2018, 07:37 AM   #117
MEPER is offline MEPER  Denmark
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Quote:
Originally Posted by Russellc View Post
Glad to see you getting somewhere with your setup! What was your device under test? A BA3 FE?

Russellc
It was just a loop back test......so output back to input to check how ARTA works and also get a feeling for how clean the built-in test generator is.


I wonder if it is possible to work with an external test generator in such a setup with ARTA.
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Old 21st July 2018, 09:14 AM   #118
MEPER is offline MEPER  Denmark
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By playing a bit with the settings in the loop back test I was able to get the noise floor just under -140 dB and 3rd harmonic which is the most dominant below -100 dB. All other harmonics are well below -100 dB. Is this considered a quality sine that can be used for testing preamps? ….would I be able to adjust P3 using such a setup? ….it will require that the distorsion of the test generator is much lower than the distortion pattern of the BA3 pre?
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Old 21st July 2018, 09:25 AM   #119
silasmellor is offline silasmellor  Denmark
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P3 Adjustment for the average Hobbyist
ARTA should be able to tell you the the+n figures, which should be close to or less than the ones i showed above. AFAIK that is fine for measuring ba-3 harmonics.

An external test generator is fine (and potentially even better than the 2i2 outputs).

Last edited by silasmellor; 21st July 2018 at 09:28 AM. Reason: Mobile phone...
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Old 21st July 2018, 09:55 AM   #120
MEPER is offline MEPER  Denmark
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Yes, I could add that in "view". It shows THD 0,00095% and THD+N = 0,0019% for the built-in sine at 1 kHz. Could be interesting to measure the sine generator I have....how clean it is.
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