RME LNI-2 DC honest talk

[johny_2000]

The only thing of interest I see in the plots are the slightly different mains spurs. For some reason the battery pack setup produced the largest peaks (at 4x, 240Hz) but is cleaner everywhere else. Of course all of this is irrelevant as it is 30dB below the RMS noise floor.

Correct. I noticed the same 240Hz peak on the battery pack.

All these low-frequency peaks came from the ether through interconnecting cables. I measured the same thing without the ADI-2 DAC at all. In fact, as soon as any cables were connected to the active notch filter, it already picked up some low-frequency EMI from the environment. So this can be ignored when assessing the overall impact of power supplies.

To double check, I often repeat the same measurement several times on different days, rigging up the tests again from scratch, and maybe it is slightly colder or warmer or the units haven't fully warmed up etc. +-0.5dB variance is nothing.

That's right! I repeated these measurements several times with all three sets on different days and times.
The graphs provided are the most representative of the results I saw during the tests.

May I suggest another measurement that would expose the effect of different mains leakage currents (the battery pack shouldn't have any), if you want to take the extra effort&time, that is?

• Add a 2-prong 12V/2A SMPS to the set of tested supplies.
• Leave the Intona in place to keep USB clean.
• Measure the unbalanced output of the RME with a normal unbalanced interconnect.
• Don't use the APU notch.
• Connect the shell/GND of the unbalanced interconnect at the receiving end at the ADC Iso to mains earth, to emulate an earth-grounded amp or similar. Alternatively, when using the original three supplies, connect the receiving end shell to the 2-prong supply, emulating an amp with such a supply.
• Play a lower level sine like -30dBFS, sort of a test signal the represents a quiet passages in music
• Look at the resultant SNR and spectra

An interesting proposal for future tests. Please draw a small schematic diagram of your proposals to better understand the conditions:

• Connect the shell/GND of the unbalanced interconnect at the receiving end at the ADC Iso to mains earth, to emulate an earth-grounded amp or similar. Alternatively, when using the original three supplies, connect the receiving end shell to the 2-prong supply, emulating an amp with such a supply.

 

[KSTR]

Nice to see this kind of thoroughness, highly appreciated.

As for your question:

 

[johny_2000]

@KSTR
Thanks for drawing.

A few more clarifications are needed:
1. What is the connection inside the DAC unit between the power supply, the center core, and the shield of the single ended cable?
2. What are the top and bottom terminals of the power supply?

 

[KSTR]

In a DAC, the output GND is connected to the supply GND, and the output signal is also referenced to GND and has low impedance, that's why everything is effectively connected together for the leakage current.

The supply is a black box with a connection to mains (of course not only a single wire) and a connection to the DAC (again not single wire). Details don't matter here, what counts is the common-mode coupling from primary to secondary side. Like the typical 1nF EMC cap connection from rectified mains input to secondary side in your typical class-II SMPS, effectively bridging the transformer. With 50/60Hz transformers it is the winding-to-winding coupling capacitance, etc.

 

[Bob from Florida]

I think you misunderstand what the BMS (battery management system) does. It isn't a regulator. It's mostly a switch to disconnect the battery in various fault conditions, plus the relatively low current bit to keep cell voltages in balance.

I did misunderstand the BMS. After digging deeper I have a better handle on it now. During my digging, I found that most 12 volt packs utilize 4 cells in series to get a nominal 12.8 volts out - parallel depends in current rating desired. The Talent Cell battery in question “cheats” by using 3 cells in series, which as @restorer-john pointed out is 11.1 volts in the 3S2P configuration at a full 3.7 volts per cell or 100 % charge. Odd that the OP was able to get 12.4 volts in his testing except it comes with a 14.6 volt charger which if the BMS allows will overcharge the battery. Reduce life in this case while saving money in manufacturing by using fewer cells in series. See the Bluetti link for some pertinent information about 12 volt batteries using 4 series cells and recommended charging, discharging, etc.

All Guide to LiFePO4 Voltage Chart 12V/48V/24V

Are you curious about LiFePO4 battery voltage? In this guide, we'll explore the details to help you understand and optimise the performance of these safe and reliable energy storage devices. Read on to learn more!

www.bluettipower.eu

 

[johny_2000]

3S2P configuration at a full 3.7 volts per cell or 100 % charge. Odd that the OP was able to get 12.4 volts in his testing

When it comes to 18650 cells, NMC (Lithium-Nickel-Manganese-Cobalt-Oxide) chemistry is the most common. This chemistry has a nominal voltage of 3.6 or 3.7 volts (depending on who you ask) and a maximum charge voltage of 4.2 volts. To prevent damage to the battery, these cells should not be discharged to below 2.5 volts to prevent damage to the battery. This is one of the reasons choosing a good BMS (battery management system) is required.

18650 voltage chart

State of Charge (%)	Voltage (V)
0	2.5
10	3.0
20	3.2
30	3.4
40	3.5
50	3.6
60	3.7
70	3.8
80	3.9
90	4.0
100	4.2

3S×4.2V=12.6V.
2P=2×3Ah=6Ah

The included charger provides a max voltage of 12.4V, so it keeps the voltage on each cell at max 4.13V, which is perfect to prevent overcharging. And of course, this is the voltage of a fully charged power bank. But I used it for 30-45 minutes to power the RME-2/4 Pro SE unit, so the overall voltage never dropped below 12V.

 

[Chrise36]

So here we go!

Test conditions:
DAC: RME ADI-2/4 Pro SE
Output: XLR
Level: +19.5 dBU
USB isolator: Intona High-Speed USB Isolator 7054-DK (1kV)
ADC: E1DA Cosmos ADCiso
APU17 Notch filter: E1DA Cosmos APU@1 kHz@0 dB preamp
Power sources: Original 3-prong grounded Power Supply, Lithium 18650x6 12.4V battery pack, RME LNI-2 DC.
Power grid 60 Hz.

View attachment 396825

View attachment 396826

View attachment 396827

The summary:
Original PS:
Noise=-124.5 dB SNR=121.9 dB THD+N=-119.5 dB

Lithium 12V battery pack:
Noise=-124.7 dB SNR=122.1 dB THD+N=-119.7 dB

RME LNI-2 DC:
Noise=-125.4 dB SNR=122.8 dB THD+N=-120.1 dB

Conclusions:
As RME stated, the ADI-2 unit is not sensitive to power supply. It has a marginal +/- 1 dB improvement in any output specifications with most complex power supplies, such as the original grounded power supply, lithium battery pack, RME LNI-2 DC module. This is a big compliment to RME's engineering team, who managed to maintain the specification with all USB sources and 12V power supplies.

You need to measure the impact of the different power supplies to amps connected in the same power strip with the different lower supplies. Older amps with high hum spec like my old Technics should reveal the differences.q

 

[johny_2000]

You need to measure the impact of the different power supplies to amps connected in the same power strip with the different lower supplies. Older amps with high hum spec like my old Technics should reveal the differences.

Chris,
You are probably talking about a speaker power amplifier connected to a DAC.
I don't have an amplifier connected to the RME ADI-2/4 Pro SE.
The advantage of this device is that it's an all-in-one unit for USB->Headphone signal transmission.
And in this particular configuration, the benefit of using a different power supply for the RME ADI-2 DAC can be ignored.

 

[Chrise36]

Chris,
You are probably talking about a speaker power amplifier connected to a DAC.
I don't have an amplifier connected to the RME ADI-2/4 Pro SE.
The advantage of this device is that it's an all-in-one unit for USB->Headphone signal transmission.
And in this particular configuration, the benefit of using a different power supply for the RME ADI-2 DAC can be ignored.

Ok you just wanted to measure your specific setup cool.

 

[PGAMiami]

My LNI-2 arrived today. Does the RME DAC sound any different with it? It sounds great with it and great without it. System is dead quiet either way. Some may ask then why buy one? My personal answer is this is a hobby, not a business. I like having it. Your mileage may vary!

More importantly perhaps is that everything about the LNI-2 says it’s a luxury product, from the packaging to the solid billet of aluminum that houses the electronics. And then my next question is whether this is a foreshadowing of more audiophile oriented product to come? I could see in a pro setting where you’re setting up your DAC in many different systems that you would want a foolproof power supply that essentially eliminates ground loop problems. But wouldn’t pros would be happy with a simpler case at a lower price.

So what’s the point of them possibly deliberately positioning this as a luxury item? Don’t know and I’m surely speculating, but I would be thrilled to buy an upgraded DAC if RME made one. Their products are a true bargain when you look at the total package.

 

[Purité Audio]

You can’t ‘upgrade’ from an RME at least not in SQ terms you can place the internals into a ‘milled from solid’ enclosure.
When are RME going to make a streamer?
Keith

 

[PGAMiami]

You can’t ‘upgrade’ from an RME at least not in SQ terms you can place the internals into a ‘milled from solid’ enclosure.
When are RME going to make a streamer?
Keith

Add this below plus RooADI and you essentially have a streamer. Works great with Roon, including bidirectional volume control

rooExtend® EXTENSION BOX FÜR ROON

Extend roon with things you love. rooExtend erweitert den Musikserver Roon in den Bereichen Zuspielung, Steuerung und Wiedergabe um vielerlei Funktionen.

shop.rooextend.com