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Loopback measurement of RME ADI-2 PRO FS (Black Edition)

exaudio

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I am going to modify the software so that you as a user can select a range of settings. My initial thought is 0.5V, 1V, 2V, 3V but suggestions are welcome.

I suggest nominal 0.85V, 2.4V and 4.75V.


I think a lot of ADC sound cards inputs would be saturated / clipping at 2.4V and 4.75V, so while @Rja4000's suggestion might be ideal for the RME's input ranges, wouldn't @jan.didden's suggestion of 0.5V, 1V, 2V, 3V provide more flexibility for a wider array of sound cards / ADCs?
 

SIY

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I think a lot of ADC sound cards inputs would be saturated / clipping at 2.4V and 4.75V, so while @Rja4000's suggestion might be ideal for the RME's input ranges, wouldn't @jan.didden's suggestion of 0.5V, 1V, 2V, 3V provide more flexibility for a wider array of sound cards / ADCs?

Right now, it's selectable for two voltages, so I imagine that going to four would not be insuperable.
 

Blumlein 88

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I think a lot of ADC sound cards inputs would be saturated / clipping at 2.4V and 4.75V, so while @Rja4000's suggestion might be ideal for the RME's input ranges, wouldn't @jan.didden's suggestion of 0.5V, 1V, 2V, 3V provide more flexibility for a wider array of sound cards / ADCs?
It depends, lots of recording interfaces take at least +16 dbu at the input which is 4.88 volts. Better ones will take 20 or 24 dbu. Now if by soundcards you mean soundcards in computers, then yes I don't think most take more than 2 volts.

If we had a choice of 4 levels I would probably choose 1, 2, 3 and 4 volts myself. Mr. Didden's .5, 1, 2, and 3 volts would work plenty well too.
 

MC_RME

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Yeah, I would love to see those 4 voltages!
Stuart, as we have a kind a roundtable here (just grabbed my beer): did Jan bring up the topic of the output level limit? The diodes D10, D12, D13, D14 limit the max output level to +18 dBu. Without these the AR II can send out a whopping +28 dBu balanced and +21 dBu unbalanced, which would be cool to squeeze out the last bit of performance with the ADI set to +24 dBu (and use it for other cool test applications as well). I of course removed these in my unit (also D1 and D2 at the TRS output), but think these diodes should be either an option via jumpers or just be removed. Prost!
 

SIY

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Yeah, I would love to see those 4 voltages!
Stuart, as we have a kind a roundtable here (just grabbed my beer): did Jan bring up the topic of the output level limit? The diodes D10, D12, D13, D14 limit the max output level to +18 dBu. Without these the AR II can send out a whopping +28 dBu balanced and +21 dBu unbalanced, which would be cool to squeeze out the last bit of performance with the ADI set to +24 dBu (and use it for other cool test applications as well). I of course removed these in my unit (also D1 and D2 at the TRS output), but think these diodes should be either an option via jumpers or just be removed. Prost!

This is good to note- when the RME-2 gets here, we're using it for an article demonstrating it combined with a Autoranger and MI for an inexpensive measurement system. I see that one of our Belgian friends is a step ahead of us...:cool:
 

jan.didden

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Yeah, I would love to see those 4 voltages!
Stuart, as we have a kind a roundtable here (just grabbed my beer): did Jan bring up the topic of the output level limit? The diodes D10, D12, D13, D14 limit the max output level to +18 dBu. Without these the AR II can send out a whopping +28 dBu balanced and +21 dBu unbalanced, which would be cool to squeeze out the last bit of performance with the ADI set to +24 dBu (and use it for other cool test applications as well). I of course removed these in my unit (also D1 and D2 at the TRS output), but think these diodes should be either an option via jumpers or just be removed. Prost!

Yes, that protection system also has to be adapted. Actually, if I knew that all soundcards could withstand +/-15 on their inputs we could just leave them out. At the time I developed this I was warned that some soundcard inputs would be damaged with anything above 5V amplitude (+ or -).

Jan
 

Rja4000

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My initial thought is 0.5V, 1V, 2V, 3V but suggestions are welcome
I was just thinking:
wouldn't that be feasible to allow user to choose nominal output at startup?
You already allow switching between 0.4V and 1V.
Why not to allow a change by, say, 3dB steps, using the 2 SE/BAL buttons to decrease/increase at power on ?
 
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jan.didden

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I was just thinking:
wouldn't that be feasible to allow user to choose nominal output at startup?
You already allow switching between 0.4V and 1V.
Why not to allow a change by, say, 3dB steps, using the 2 SE/BAL buttons to decrease/increase at power on ?

That is exactly what I had in mind! Maybe not 3dB steps, but more like 6dB steps.
No sure when I get to it; SIY has me chained to his workbench, ;-) but probably sometime coming weeks.

Jan
 

jan.didden

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Just realized there is a limit in the current hardware, as the ADC ref is 4.1V. So the controller can process max 4.1V peak which is about 2.8Vrms.
There's an easy way to like double it but that would require a hardware change ...

Jan
 

Rja4000

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That is exactly what I had in mind! Maybe not 3dB steps, but more like 6dB steps.
No sure when I get to it; SIY has me chained to his workbench, ;-) but probably sometime coming weeks.

Jan
Hi @jan.didden

I just see that you posted an update on your website and a new software is available, supporting a range selection from 0.5V to 3V in 0.5V increments :)

Nice !! :)
 

polmuaddib

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Hello,
I bought RME ADI-2 Pro FS BE yesterday and wanted to try measuring my analog stereo preamp. Hope I didn't make too many mistakes, but if I did, I appreciate the input and help.
I connected ADI's output to Preamp's input and then Preamp's output to ADI input. That is now measuring Preamp, because i supposed that ADI is more accurate then preamp.
So, this is the result.
If you want more info, please ask and comment.
The preamp is Jeff Rowland Capri, and all connections were balanced.
Thanks
Capri preamp.jpg
 

Rja4000

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Hello,
I bought RME ADI-2 Pro FS BE yesterday and wanted to try measuring my analog stereo preamp. Hope I didn't make too many mistakes, but if I did, I appreciate the input and help.
I connected ADI's output to Preamp's input and then Preamp's output to ADI input. That is now measuring Preamp, because i supposed that ADI is more accurate then preamp.
So, this is the result.
If you want more info, please ask and comment.
The preamp is Jeff Rowland Capri, and all connections were balanced.
ThanksView attachment 121119
Hi

I think you should show the generator settings.
And what's 0dBFS level ? (Which range is used for output and input on RME, in other words ?)
 

polmuaddib

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Hi,
I will screenshot Generator level next time. REW didn't save it. Just saved RTA window.
RME ADI was set to +13dBU input level, REW Generator was at -3.0 and JR preamp was at about 92 (that is in percentage, cause it goes from 0 to 100), but i didn't measure output voltage on the preamp. I just messed with volume of the preamp and generator to get 1 khz peak to 0 dBFs and couldn't get it. As soon as i went with preamp over 94, clipping occured. Then I changed to dBc and 1 khz level was at 0. Happy that I got some logical picture, I posted.
So these results are not exact, but some ballpark....
How should I do it better? Should i use voltmeter on other XLR output (Left or right, which i am not using)?
What settings should be on ADI?
Thank you.
 

Rja4000

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Hello,
I bought RME ADI-2 Pro FS BE yesterday and wanted to try measuring my analog stereo preamp. Hope I didn't make too many mistakes, but if I did, I appreciate the input and help.
I connected ADI's output to Preamp's input and then Preamp's output to ADI input. That is now measuring Preamp, because i supposed that ADI is more accurate then preamp.
So, this is the result.
If you want more info, please ask and comment.
The preamp is Jeff Rowland Capri, and all connections were balanced.
ThanksView attachment 121119
Hi

A few quick comments:

- switching UoM to dB would be more readable than %. The limiting factor is obviously noise, so dB makes even more sense (88dB SNR is more readable than 0.0039%)

- Make sure and show that measurement is done for a range limited to 20Hz-20kHz, otherwise noise may be out of display. Also, sampling rate (44k or 48k), window type and size should be specified to allow others to duplicate

- Input level and gain are arbitrary
Given Amir's standard is 2Vrms (unbalanced) or 4Vrms (balanced), you should probably use those as preamp input level (and 0 gain - RME input level = RME output level) per default.
Display the dashboard with those values.
If THD is then too high, lower input level to a value where SINAD is best. Specify this input value.
If Noise is still predominant, do the opposite: raise input level until THD starts to be predominant and you get the best SINAD.
Those are probably the 2 most useful dashboards

- If you have time you may check the gain limits for best SINAD with input level at 4V (or 2V)

- Try to measure 31 tones
(Don't saturate RME output, and show input level)

- Try to measure frequency response at 48k sampling rate or higher

- Channel balance vs gain level is useful

- IMD (Amir uses SMPTE IMD) vs input level and crosstalk vs frequency are other interesting measurements
...

The RME performance is way better than what you measure here.
It still makes sense to optimize it, as an habit, though.
So, at least, measure with RME input and output ranges where your level on RME is between -0.5 dBfs and -6dBfs.
For 4Vrms balanced, RME range should be +19dBu and level on REW at -4.7dBfs.
For 0 gain on preamp, RME should show the same -4.7dBfs with +19dBu range. If possible, check the preamp input and output voltages with a true RMS multimetre with a 80Hz signal to make sure.
There are other tricks to improve RME performance even further, but you don't need that here.
 
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polmuaddib

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Thanks for comments,
I will try to do all those things on the next go.
One thing, though. When you say that RME performance is way better then I measure... Maybe I wasn't clear or I am not getting your point right, I was trying to measure a different component, not RME. I saw RME measurements form others and I know it is good. I measured a JR Capri preamp. Maybe, when I said loopback, I didn't use that right.
 

Rja4000

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Thanks for comments,
I will try to do all those things on the next go.
One thing, though. When you say that RME performance is way better then I measure... Maybe I wasn't clear or I am not getting your point right, I was trying to measure a different component, not RME. I saw RME measurements form others and I know it is good. I measured a JR Capri preamp. Maybe, when I said loopback, I didn't use that right.
I say RME is way better because that means that the measures you have here are actually showing your preamp performance.
If it was closer to the RME (say, less than 10dB worse than RME), you'd have to make sure to optimize the loopback RME performance, in order to lower the influence of RME on your measurements results.
 

polmuaddib

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Right. Thanks. So, I should first learn how to properly setup RME, do loopback and then go to preamp...
 

Rja4000

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It's always interesting to check the tested device's specs, to know what to expect.

Here, you read that max Output level is 13.5Vrms (+24.8dBu)
(I supposed it's original S, not S2, version)

and expected THD+N is <0.001% @2Vrms Output
(We don't know if that's measured with balanced or unbalanced, though)

Your measurements are far off... but that may be for a different gain
(Much lower - Max gain being 14dB)
Or they cheat...
(Which is always a possibility)

JR Capri Specs.png
 
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