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Focusrite Scarlett 2i2 Gen3 - Measurements in loopback mode

pma

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#1
Focusrite Scarlett 2i2 Gen3

The main review by @amirm is here:
https://www.audiosciencereview.com/...rlett-2i2-audio-interface-gen-3-review.10187/

I have decided to add several measurements in loopback mode with this soundcard

1. THD and THD+N at 1kHz, XLR input

2i2_TRS_XLR_loop_1k_2.png


This is not bad, considering the price. THD is quite low, THD+N (SINAD) is higher but still below 0.001%. The main contributor to higher THD+N is DAC output noise. ADC is quieter.

2. CCIF IMD 19+20kHz

2i2_TRS_XLR_loop_CCIF.png

I am not very happy with this result. Though difference tone 1kHz is low, we can see skirts of H3 and higher harmonics near the test tones that indicate to worsen high frequency linearity. This is my favourite test and I miss it in most reviews here.

3. THD vs. frequency at -3dBFS

2i2_TRS_XLR_loop_thdfreq.png

Good up to 1kHz and then we can see rise of distortion with frequency. Mostly the 3rd harmonic. We can see the effect in CCIF measurement here above.

4. THD and THD+N vs. amplitude, at 1kHz

2i2_MSYS_loop_thdampl.png


THD result is quite good, THD+N result is not so good and is affected mostly by the DAC noise. Pity.

Conclusion

This is not a bad soundcard, taking into account its price about $140. I appreciate the absence of mains spuriae, balanced inputs and outputs and reasonable THD. DAC noise could be lower.
 
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pma

pma

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Thread Starter #2
Two ways to go to standard XLR cable from the 2i2 TRS outputs

2i2_TRStoXLR.JPG


Left channel goes through Neutrik TRS/XLRmale adapter, Right channel through Neutrik TRS/XLR 1m cable


Immunity to signal ground loops (CMR) is very good. Below is a measurement of a preamplifier with balanced I/O that is placed in another room and connected via 2 XLR-XLR cables of 10m length with the Focusrite. No sign of mains hum frequencies. The PC notebook is supplied from its 2 prong plug adapter, that means that there is no additional loop created by mains PE wire between the PC and the preamp. The preamp is class I device.

2i2_PRE.png
 

restorer-john

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#3
Two ways to go to standard XLR cable from the 2i2 TRS outputs

View attachment 142591

Left channel goes through Neutrik TRS/XLRmale adapter, Right channel through Neutrik TRS/XLR 1m cable


Immunity to signal ground loops (CMR) is very good. Below is a measurement of a preamplifier with balanced I/O that is placed in another room and connected via 2 XLR-XLR cables of 10m length with the Focusrite. No sign of mains hum frequencies. The PC notebook is supplied from its 2 prong plug adapter, that means that there is no additional loop created by mains PE wire between the PC and the preamp. The preamp is class I device.

View attachment 142592
@pma your last plot (arta) above is 96kHz sampling but only showing 20kHz upper most freq. The noise rise is chopped off the display, unlike the IMD where you display a 40kHz upper most freq.

I have both the 2i2v2 and the 2i2v3 and they perform best at 48kHz. Their sweet spots are also much lower output voltages, around 381mV (2i2v2) and no gain on the input pots (put them at zero)

2i2v2 (unweighted):
1626853580478.png


I'll run the same on the 2i2v3 tomorrow and find the sweet spot for THD and noise and levels.
 
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pma

pma

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Thread Starter #4
I have both the 2i2v2 and the 2i2v3 and they perform best at 48kHz. Their sweet spots are also much lower output voltages, around 381mV (2i2v2) and no gain on the input pots.
I tend to have a different opinion. In your "sweet spot" you get THD=0.00034%, but THD+N is high = 0.0038%. This is the result of low level + high intrinsic noise. On contrary, if you see my post #1, I get THD = 0.00035% (same as you) at much lower THD+N = 0.00089%, in a loop, close to full XLR input level. This is a significant difference of 13dB less noise. Try to think about it thoroughly :).

Regarding the plot in post #2 that you have mentioned, the DAC noise is amplified by the preamp measured so the THD+N is higher. It is not a loopback measurement of the soundcard itself, but the preamp with gain is inserted, in a loop of 20m total length. This was to demonstrate very good CMR of the 2i2 input amplifier.

2i2_TRS_XLR_loop_1k_2.png
 
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restorer-john

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#5
Don't forget, yours is A weighted, mine (2i2v2) is not. A-weighting gives an almost 10dB response reduction by 20KHz. :)

Anyway, we'll do an apples to apples comparison with my 2i2v3 and see how close they are. Will be interesting. They really are great little interfaces aren't they?
 
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pma

pma

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Don't forget, yours is A weighted, mine (2i2v2) is not. A-weighting gives an almost 10dB response reduction by 20KHz. :)
Again wrong, John. The THD+N in post#1 is measured without weight with BW = 20Hz - 20kHz. You are referring to measurement with PRE inserted which is irrelevant to card noise. My humble suggestion for you is to read thoroughly before you write an opinion, because your opinion is valid for many members. However, you have to suppose that I will be strict in engineering terms and interpretations of results.

BTW, my measurements strictly correspond to Amir's results in his review. I have just added CCIF and THD(freq) to show the worse linearity at higher frequencies.
 

restorer-john

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#7
Again wrong, John. The THD+N in post#1
Ah. I just looked your post above which is A-WTD:

1626855902262.png



Apologies. In the interests of like comparisons, make them either all UWTD or A-WTD, not a mixture of the two.
 

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pma

pma

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Ah. I just looked your post above which is A-WTD:

Apologies. But in the interests of like comparisons, make them either all UWTD or WTD, not a mixture of the two.
Well, accepted. But the key is that you picked up the measurement of the preamp and not the card loopback. And it all was explained in the posts. The problem of web discussions is their shallowness, especially if many different topics are to be replied.

The main post is post #1 and the REW measurement gives all the info. Measuring bandwidth, noise, distortion, noise + distortion. Only you have to open the image and read the description. THD+N = 0.00089% (20 - 20000Hz unweighted) makes 101dB SINAD, at THD = 0.00035% (valid just for the measurement, may differ with warm-up). I think the loop SINAD 101dB cannot be beaten by finding the "sweet spot". Anyway, There are also plots of THD and THD+N vs. level in post #1. THD/level shows some interesting inflection. Most probably if it was measured after longer period of warm-up the numbers below 0.001% might be a bit different.
 

restorer-john

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#9
It's all good Pavel. I looked at your last ARTA plot and assumed they were all A-WTD after a quick glance. :)

We'll see how different my setup is with the 2i2v3 tomorrow (same settings- 1M TRS-XLR cables are my standard) My PC is sitting on the same ground/earth as all the test gear and the USB outer/0V, so I get some issues with (what I think is) USB packet noise sometimes when going single ended/unbal. 8/16kHz spikes.

Do you have any experience with high speed USB isolators?
 
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pma

pma

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Thread Starter #10
Loopback TRS ==> XLR, 44.1kHz, unweighted (BW 22kHz). OUT = 0dBFS, level adjusted by monitor volume pot to get input close to 0dBFS. THD+N slightly below 0.001%, SINAD slightly above 100dB. ARTA.

In a long term run, THD slightly varies around 0.0005%.

2i2_SINAD_unw.png
 
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pma

pma

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Thread Starter #11
Some more measurements .....

Headphone output
is the weakest point of this soundcard.
2i2_head_thd.png

However, the distortion is acceptable up to some 200mV with 50 ohm load. The good point is low output impedance about 1 ohm. I think they use the ancient cheap JRC4556 opamp in the headphone amp which would explain this distortion behaviour.

Maximum output voltage
from TRS balanced output is 4.8Vrms
2i2_maxout.png


Noise measurements

Wideband output ultrasonic noise is about 27mVrms
2i2_noisetime.png


It is a result of sigma-delta DAC noise shaping which starts above audible frequencies
2i2_noisespectrum_190kHz.png


It has however "noise shape" with no high individual spectral lines even at higher measuring bandwidth
2i2_noisespectrum_780kHz.png
 
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AnalogSteph

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#12
I think they use the ancient cheap JRC4556 opamp in the headphone amp which would explain this distortion behaviour.
Close but no cigar. NJM8065 I think, i.e. the NJM4565 "reboot" - a much better load driver than the 4558 but still nothing special by modern standards, certainly for a headphone driver. Bit of a dubious choice for this position, I don't think the 0.5-0.75 mA more idle current for a 4580/8080 would have killed them (it wouldn't go much louder but distortion would have been a good bit better). Last time I checked it should also be possible to accommodate both SOP-8 and DMP-8 with a single footprint, so even the trusty NJM4556A of O2 fame may potentially have been an option even if its power hunger would have been more significant (almost 4 mA more in idle).
 
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pma

pma

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Close but no cigar. NJM8065 I think, i.e. the NJM4565 "reboot"
Thank you! Yes the 4556A should be better than what I have measured, according to the datasheet curves. I will not bother with re-soldering, as I do not need the headphone output for anything but functional monitoring.
 
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