Focusrite Scarlett 6i6 2nd gen measurements

[Matias]

I am totally new to doing loopback measurements in REW, this is my first try, so please correct me if there is a better way to do this.

I have a Focusrite Scarlett 6i6 2nd generation audio interface and connected the Output 1 line out into the Input 3 line in using a 1/4" TS cable with about 2 meters (7 feet) that I have here. Using a 1 kHz sine wave full scale and set the monitor level to the max.

I tried to compare the difference between the stock switching mode power supply (SMPS) and the iFi iPower SMPS.

While measuring I noticed the noise floor raised and lowered with ambient noises. I tried closing the doors and windows and grab the screen shot in best moments, but microphony definitely has been picked, specially between 80 to 300 Hz.

Questions:
1. Is there a better way to measure without picking up microphonics? In the middle of the night maybe?
EDIT: fixed here https://www.audiosciencereview.com/...tt-6i6-2nd-gen-measurements.12761/post-379502

2. Are these lots of harmonics OK? I found this to be quite noisy. I expected around -100dB some 2nd and 3rd, sure, but not the higher ones.

3. Any settings in REW I should use to improve these measurements?

 

[RayDunzl]

What happens as you reduce the tone level?

I think REW throws some harmonics unless you back it off a little.

(Maybe it was an earlier version... Not seeing it today.)

 

[naagratrax]

I am totally new to doing loopback measurements in REW, this is my first try, so please correct me if there is a better way to do this.

I have a Focusrite Scarlett 6i6 2nd generation audio interface and connected the Output 1 line out into the Input 3 line in using a 1/4" TS cable with about 2 meters (7 feet) that I have here. Using a 1 kHz sine wave full scale and set the monitor level to the max.

I tried to compare the difference between the stock switching mode power supply (SMPS) and the iFi iPower SMPS.

While measuring I noticed the noise floor raised and lowered with ambient noises. I tried closing the doors and windows and grab the screen shot in best moments, but microphony definitely has been picked, specially between 80 to 300 Hz.

Questions:
1. Is there a better way to measure without picking up microphonics? In the middle of the night maybe?
2. Are these lots of harmonics OK? I found this to be quite noisy. I expected around -100dB some 2nd and 3rd, sure, but not the higher ones.
3. Any settings in REW I should use to improve these measurements?

View attachment 59791
View attachment 59790
View attachment 59792

Are you happy mate with the iFi iPower SMPS ? i seen a post from Amir in 2018 that it's make no difference with the stock psu

 

[RayDunzl]

I have a Clarett 4 Pre USB

REW 1kHz -0.90dBfs -> USB -> USB Playback 3 -> Output 3 -> guitar cable -> Line Input 7 -> USB Input 7 -> REW matching your -7.17dBfs

Look familiar?


---


-3.30dBfs source at REW

There's no "volume knob" in this path, though.

 

[LTig]

While measuring I noticed the noise floor raised and lowered with ambient noises. I tried closing the doors and windows and grab the screen shot in best moments, but microphony definitely has been picked, specially between 80 to 300 Hz.

Questions:
1. Is there a better way to measure without picking up microphonics? In the middle of the night maybe?

Repeat the test and knock on the TS cable, does this change the noise floor? If yes much more than ambient noises? If yes try another cable, preferably a balanced one.

 

[Matias]

I deleted my previous post because it was wrong.

I am using volume knob at maximum, which I measured with a multimeter 2.0V between tip and sleeve of the cable.

Now measuring with -12dB on the generator things are a lot cleaner too.

 

[Matias]

Repeat the test and knock on the TS cable, does this change the noise floor? If yes much more than ambient noises? If yes try another cable, preferably a balanced one.

Yes, knocking on the cable, the table or even speaking loud the noise floor rises.
I wish I had a short 1/4" TRS here to test but I don't... Would have to order it specially for measuring.

 

[Matias]

I have a Clarett 4 Pre USB

REW 1kHz -0.90dBfs -> USB -> USB Playback 3 -> Output 3 -> guitar cable -> Line Input 7 -> USB Input 7 -> REW matching your -7.17dBfs

View attachment 59797

Look familiar?

-3.30dBfs source at REW

View attachment 59798

There's no "volume knob" in this path, though.

Interesting. I was looking into upgrading my interface to a Clarett 4Pre USB.
Are you using the same configs I set on the right of my prints, with FFT length and averages and window the same?

 

[LTig]

Yes, knocking on the cable, the table or even speaking loud the noise floor rises.
I wish I had a short 1/4" TRS here to test but I don't... Would have to order it specially for measuring.

Disconnect the cable and knock on the table or speak loud.

 

[RayDunzl]

Are you using the same configs I set on the right of my prints, with FFT length and averages and window the same?

Probably not... Just wanted to show the harmonics ADC likes to create at higher input levels, and matching your levels.

Let me look again.

 

[Matias]

Disconnect the cable and knock on the table or speak loud.

Yes, it picks up microphony... Specially around 80-300Hz.

 

[LTig]

Yes, it picks up microphony... Specially around 80-300Hz.

How high does the noise floor rise, cable disconnected?

 

[Matias]

Here are some multitone measurements with stock and iPower SMPS.

Generator I used the following settings, just before clipping.

 

[Matias]

How high does the noise floor rise, cable disconnected?

This is multitone with all cables disconnected. How come it still measures something??

 

[Matias]

I am very impressed how much microphony picks up on an unbalanced cable. And here is a quite room. I can only imagine how much noise a guitar amplifiers picks from a guitar cable on a live concert!

Edit: forget this, I left a microphone connected, stupid mistake.

 

[LTig]

This is multitone with all cables disconnected. How come it still measures something??

Looks like crosstalk from output to input.

 

[LTig]

I am very impressed how much microphony picks up on an unbalanced cable. And here is a quite room. I can only imagine how much noise a guitar amplifiers picks from a guitar cable on a live concert!

The real problem is that even an open (not connected) input picks up microphony. Next step would be to short the input.

 

[Matias]

The real problem is that even an open (not connected) input picks up microphony. Next step would be to short the input.

Thanks! You nailed it. I had inputs with no cables but I left them out to the monitors, this was causing the microphony! I told you I was noob.
Edit: even worse! I had a microphone plugged into input 1. This was routing to the monitor outs. This explains a lot, including my stupidity.

Here are the multitones with no inputs enabled.

No other inputs to the monitor outputs, just the software signal.

 

[Matias]

Now for reference, with the noise generator 1kHz at full scale, the volume knob at 10 o'clock which would be a good listening level for me, this is how they both measure. Extremely low distortion below -130dB or so. Noise from the power supply is dominating.

I guess I should stick to my 6i6 2nd gen and skip the Clarett 4Pre USB then.

And multitone.

 

[Matias]

And to fix the first post, this is the 1kHz full scale signal into maximum volume (2.0V) monitor out with no inputs enabled.