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

[vitalii427]

I just performed some measurements on the RME ADI-2 Pro fs (initial version) in loopback mode for the various methods:

RME ADI-2 Pro fs Loopback @4Vrms
Output and input +19dBu range
Balanced Y Cable on both outputs (Main out)
Balanced Y Cable on both inputs and M/S mode

View attachment 46338
SINAD = 112dB


RME ADI-2 Pro fs Loopback @2.5Vrms
Output and input +13dBu range
Balanced Y Cable on both outputs (Main out)
Balanced Y Cable on both inputs and M/S mode
View attachment 46339
SINAD = 114dB


RME ADI-2 Pro fs Loopback @2.5Vrms
Input +13dBu range
Output Balanced Phone mode - Low gain (+13dBu)
Balanced cables of both channels to each input
(So NO output sum)
RME input in M/S mode
View attachment 46340
SINAD = 115dB !


I also received today my Linear Audio Autoranger II

RME ADI-2 Pro fs Loopback through Autoranger II @4Vrms
Autoranger in 1V output mode
RME Output +19dBu range @4Vrms
RME Input +4dBu range
Balanced Y Cable on both outputs (Main out) to Autoranger Balanced in
Balanced Y Cable from Autoranger Balanced out to both RME balanced inputs and RME input in M/S mode
View attachment 46337
SINAD = 110dB
or 2dB loss vs direct RME loopback


RME ADI-2 Pro fs Loopback through Autoranger II @2.5Vrms
Autoranger in 1V output mode
RME Output +13dBu range @2.5Vrms
RME Input +13dBu range
Balanced Y Cable on both outputs (Main out) to Autoranger Balanced in
Balanced Y Cable from Autoranger Balanced out to both RME balanced inputs and RME input in M/S mode
View attachment 46341
SINAD = 110dB

All this means the loopback SINAD for the Autoranger II alone should run somewhere between 112dB and 123dB...
Should be good enough to perform basic measurements on speaker amps.

1V is a bit low. Can you do some more tests?
1) RME at 1V output without Autoranger
2) Then 1V to Autoranger (gain 0 dB)
3) Then hold Autoranger at 0 dB and set RME output level 4V and 2.5V

 

[Rja4000]

1V is a bit low. Can you do some more tests?
1) RME at 1V output without Autoranger
2) Then 1V to Autoranger (gain 0 dB)
3) Then hold Autoranger at 0 dB and set RME output level 4V and 2.5V

So what you suggest is that I measure the Autoranger at unity gain ?
That's not really the use case... But I may give it a try.

I'll create a separate thread for that though, with more Autoranger measurements and some Stereo amps tested @5W.
I have a few legacy amps at hand:
Naim NAIT3, Pioneer A400X, an old Technics, Arcam P75, Linn Majik I (first generation), Yamaha AX470...
Also a (more recent) Musical Fidelity M6PRX (my main Amp).
And some Bluesound Powernodes N150 too...

But that's not the subject here.

 

[vitalii427]

So what you suggest is that I measure the Autoranger at unity gain ?
That's not really the use case... But I may give it a try.

I’m going to order Autoranger too and just curious of its performance. About the use case: with +24 dBu input why measure amps at 1V if you can control attenuation??

 

[Rja4000]

with +24 dBu input why measure amps at 1V if you can control attenuation??

Well, it's more secure, isn't it ?
Don't want to risk breaking the RME input if there is a spike @50Vrms or so...

 

[vitalii427]

Well, it's more secure, isn't it ?
Don't want to risk breaking the RME input if there is a spike @50Vrms or so...

Disagree. First I’m pretty sure input can tolerate more than 50Vrms. If you doubt you can use at least 4V which is still 12 dB better than 1V

 

[Rja4000]

Disagree. First I’m pretty sure input can tolerate more than 50Vrms. If you doubt you can use at least 4V which is still 12 dB better than 1V

It looks to me that the RME is more efficient around +10dBu (2.5Vrms) than at 4Vrms.

Other than that, the Autoranger is designed to standardize output to either 1Vrms or 0.4Vrms (with a 6dB variation window).
If you want it to have an output level around +4Vrms, you'll have to fix the attenuation/gain manually... or to ask Jan Didden to modify the design.
(If you're at this, please ask to use an Arduino or similar to control the device. Then we'd have a chance to feed back the Voltages and gain to the PC)

 

[Blumlein 88]

What's the output impedance of the auto ranger?

 

[Rja4000]

What's the output impedance of the auto ranger?

I dont know.
Input impédance is 10k ohm, but output is not specified. I'll ask Jan.

 

[Rja4000]

Disagree. First I’m pretty sure input can tolerate more than 50Vrms. If you doubt you can use at least 4V which is still 12 dB better than 1V

Well, I found this on RME forum
https://forum.rme-audio.de/viewtopic.php?pid=134010#p134010

"The protection is designed to work up until 21 Vrms or 60 Vpp or 28.7 dBu unbalanced and 34.7 dBu balanced. Above that expect some smoke signs coming out of the unit"

That's a post from Mathias (@MC_RME), I guess.

 

[MC_RME]

There is some screwed-up logic here. How can the AutoRanger give out higher voltages than the ADI can accept? The AutoRanger works internally with +-15V...it's not a passive attenuator.

With regards to the ADI, the use case of the AutoRanger is not to provide the same level for measurement no matter what you feed it. It has a big level range 'window' in auto mode so that won't happen anyway. The use case - especially in combination with an ADI that already includes hardware based level steps - is to scale down too high input levels, typically from power amps, to measure them without overloading the ADI's input.

Also to get the best SNR and THD+N one should indeed use higher levels as 1 V. I successfully used a 2 V setting (custom EPROM from Jan) which equals +13 dBu range in the ADI. Even 3 V would be possible, and that is how I use the AutoRanger by doing what vitalii427 suggested - use the manual mode. I set the ADI to +19 dBu and dial down the amp's signal with the Autoranger manually so they best fit.

 

[MC_RME]

What's the output impedance of the auto ranger?

The AR II has 50 Ohm series resistors on all output signals, means 100 Ohm output impedance for XLR.

 

[Rja4000]

I successfully used a 2 V setting (custom EPROM from Jan) which equals +13 dBu range in the ADI.

I sent an email to Jan to ask for the 2V output this morning. If that's simply an Eprom swap, that's really a no-brainer.

One annoying thing with the 1V range is that it switches on 6dB more attenuation when level reaches 1.27Vrms, which is just too high to be able to use the +4dBu range on the ADI.

 

[vitalii427]

Well, I found this on RME forum
https://forum.rme-audio.de/viewtopic.php?pid=134010#p134010

"The protection is designed to work up until 21 Vrms or 60 Vpp or 28.7 dBu unbalanced and 34.7 dBu balanced. Above that expect some smoke signs coming out of the unit"

That's a post from Mathias (@MC_RME), I guess.

Thanks for the info! Sure it was an exaggeration on my part. I was too lazy to search actual info.

There is some screwed-up logic here. How can the AutoRanger give out higher voltages than the ADI can accept? The AutoRanger works internally with +-15V...it's not a passive attenuator.

With regards to the ADI, the use case of the AutoRanger is not to provide the same level for measurement no matter what you feed it. It has a big level range 'window' in auto mode so that won't happen anyway. The use case - especially in combination with an ADI that already includes hardware based level steps - is to scale down too high input levels, typically from power amps, to measure them without overloading the ADI's input.

Also to get the best SNR and THD+N one should indeed use higher levels as 1 V. I successfully used a 2 V setting (custom EPROM from Jan) which equals +13 dBu range in the ADI. Even 3 V would be possible, and that is how I use the AutoRanger by doing what vitalii427 suggested - use the manual mode. I set the ADI to +19 dBu and dial down the amp's signal with the Autoranger manually so they best fit.

Thanks your time, Matthias! You’ve answered my question that I didn’t even have time to ask. Your input is very valuable.

 

[Rja4000]

There is some screwed-up logic here. How can the AutoRanger give out higher voltages than the ADI can accept?

I thought he wanted to connect the amp to the RME directly, without the Autoranger. In that case, there is a risk to break it.

With regards to the ADI, the use case of the AutoRanger is not to provide the same level for measurement no matter what you feed it. It has a big level range 'window' in auto mode so that won't happen anyway. The use case - especially in combination with an ADI that already includes hardware based level steps - is to scale down too high input levels, typically from power amps, to measure them without overloading the ADI's input.

Not a fixed level, but a level within a 6dB window around either 1V or 0.4V, indeed.
The goal is clearly to lower voltage from an amp to a level acceptable for the ADC (the Autoranger accepts up to 100Vrms at its input).
My post was not clear.

Also to get the best SNR and THD+N one should indeed use higher levels as 1 V. I successfully used a 2 V setting (custom EPROM from Jan) which equals +13 dBu range in the ADI. Even 3 V would be possible, and that is how I use the AutoRanger by doing what vitalii427 suggested - use the manual mode. I set the ADI to +19 dBu and dial down the amp's signal with the Autoranger manually so they best fit.

Thanks a lot for the hint.
I'll give it a try.

I updated my previous post for clarity.

 

[SIY]

I have a lot of measurements of the Autoranger set for appearance in AudioXpress. I'm hoping they'll be useful. It challenges the APx555 B Series. The output voltages I saw were about 1.7V, so this should help, even without the new modified version.

And an RME-2 FS is on the way here. Put together, these will be an excellent measurement tool.

edit: Jan is sitting across the table from me at the moment.

 

[jan.didden]

I sent an email to Jan to ask for the 2V output this morning. If that's simply an Eprom swap, that's really a no-brainer.

One annoying thing with the 1V range is that it switches on 6dB more attenuation when level reaches 1.27Vrms, which is just too high to be able to use the +4dBu range on the ADI.

Yes 50/00 ohms Rout is correct. To the level switching: the kit now includes the updated controller which has two settings, 1V and 2V nominal. As Matthias mentioned, that is a nominal value; the AR typically switches up or down at 0.7 or 1.4 times this value.

Just discussed this with SIY (over a cup of coffee no less) and 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.

Jan

 

[Rja4000]

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

Sounds great !
Will that be available as an (Eprom) update ?

I suggest nominal 0.85V, 2.4V and 4.75V.
That would allow max range values (×1.4) below the limit of +4dBu, +13dBu and +19dBu, for optimal use of the RME ranges

 

[Rja4000]

Just discussed this with SIY (over a cup of coffee no less)

Are you both in Belgium, or in the US?
If you're in Belgium, I may join you
And bring some beers...

 

[SIY]

Are you both in Belgium, or in the US?
If you're in Belgium, I may join you
And bring some beers...

We’re in the US, but you can still bring beer.

 

[jan.didden]

We could swap beer from my hometown Turnhout, brewery 'Het Nest'.
https://www.brouwerijhetnest.be/en

Sorry for OT.

Jan