Measurements of RME ADI-2 DAC and Headphone Amp

[MC_RME]

The goal here was to be fully galvanically isolated, right? Charging the battery while using it prevents that. Then there is no difference to using the ADI via its own power supply.

 

[entrophy]

I was assuming your recommendation was based on the notion that it's galvanically isolated. Because otherwise, if it can't be used in a permanently charged state you'd be inviting a whole bunch of other issues, like voltage drops when depleting the cells. So how does the XT behave when nearing a full discharge, will it cut off or just keep discharging? And did you measure voltages while discharging? Is it built to maintain 12V (+-tolerances) throughout its rated capacity?

 

[Alan S]

... I don't believe that.

Nothing is unbelievable.

 

[badboygolf16v]

My XTPower is on the way, but maybe I should have got the TalentCell 12V/9V as that could power both my ADI-2 and Koss ESP/95X and RPi at the same time!

 

[MC_RME]

My XTPower is on the way, but maybe I should have got the TalentCell 12V/9V as that could power both my ADI-2 and Koss ESP/95X and RPi at the same time!

Yes, if you need both voltages that seems to make sense. But the next question is: what do you want to achieve with the battery operation? If it's perfect audio nirvana then a combined solution might not work perfectly, and you would need two separated powerbanks, one 9V, one 12V. At least in my measurement applications using two devices from the same powerbank sometimes fails with noise showing up again.

 

[MC_RME]

I was assuming your recommendation was based on the notion that it's galvanically isolated. Because otherwise, if it can't be used in a permanently charged state you'd be inviting a whole bunch of other issues, like voltage drops when depleting the cells. So how does the XT behave when nearing a full discharge, will it cut off or just keep discharging? And did you measure voltages while discharging? Is it built to maintain 12V (+-tolerances) throughout its rated capacity?

You misunderstood my post. Let me explain again: the goal with battery usage is to get rid of SMPS leakage current, and any capacitive coupling to the power grid (and earth/ground connections, of course). The moment you connect a SMPS charger to the powerbank that advantage is lost. I also don't see why a powerbank should or need a galvanic isolation between its charging port and its output. No one expects that. After all it's a relatively cheap powerbank...

 

[Alan S]

You misunderstood my post. Let me explain again: the goal with battery usage is to get rid of SMPS leakage current, and any capacitive coupling to the power grid (and earth/ground connections, of course). The moment you connect a SMPS charger to the powerbank that advantage is lost. I also don't see why a powerbank should or need a galvanic isolation between its charging port and its output. No one expects that. After all it's a relatively cheap powerbank...

How strong power supply noise can ADI-2 DAC handle? How about 100mVp-p?

Edit:
About "handle", I mean “does not degrade the sound quality”.
Many users have bought expensive linear power supply for their ADI-2 DACs, but I think it is not necessary.
I asked so because I just have an idle power adapter, I'm wondering if it could be suitable for ADI-2 DAC.
Here is more information about the adapter, please see GSM40A12 (12V).
https://www.meanwell.com/webapp/product/search.aspx?prod=GSM40A

 

[solderdude]

How strong power supply noise can ADI-2 DAC handle? How about 100mVp-p?

Common mode or differential mode ?
Which frequency band(s) ?
According to what standard ?
What do you mean with 'handle', to the point of influence (and how much) or becoming defective ?

Your question is way too general to answer properly.

 

[McFly]

This whole power supply movement is the biggest rolleyes thing since cables became an issue. Must be some manufacturers making serious bank on people’s ... stupidity ..for lack of a better term. Kudos to them.

 

[Alan S]

Common mode or differential mode ?
Which frequency band(s) ?
According to what standard ?
What do you mean with 'handle', to the point of influence (and how much) or becoming defective ?

Your question is way too general to answer properly.

I got you, will improve.

 

[MC_RME]

How strong power supply noise can ADI-2 DAC handle? How about 100mVp-p?

Edit:
About "handle", I mean “does not degrade the sound quality”.
Many users have bought expensive linear power supply for their ADI-2 DACs, but I think it is not necessary.
I asked so because I just have an idle power adapter, I'm wondering if it could be suitable for ADI-2 DAC.
Here is more information about the adapter, please see GSM40A12 (12V).
https://www.meanwell.com/webapp/product/search.aspx?prod=GSM40A

I have the GSM36. I bought it to check the differences in leakage current to our own power supplies. Basically it is not worth the extra money expense, because IF you have an audible problem with leakage current THEN going from 0.25 mA of our PS to around 0.08 mA of the Meanwell does not bring enough advantage. It's exactly what one could easily calculate/show in dB: -10 dB. A noticeable and worth it solution requires at least -20 to -40 dB, or a leakage current of only 0.002 mA (to repeat: IF you have a problem in your specific setup and combination of devices). A linear power supply does not have leakage current problems, but usually emits a strong magnetic field that might unexpectedly introduce hum in your setup as classic ground loop.

But back to your question: apart from a bit lower leakage current the Meanwell is in no way better than our supplied PS, the tech specs are more or less identical and more or less industry standard. The ADI uses heavy filtering at the DC input, then processes the incoming energy by a switched mode supply, then cleans the newly generated voltage by normal, then super low noise voltage regulators. Exactly as mentioned in the manual.

While I have never tried the maximum ripple and noise tolerance at the DC input I expect ripple tolerance to be around +/- 3 Volt (derived from the simple fact that the input voltage range is 9 V to +15 V, with 12 V as default). Noise might be less, but how to measure this without defining 'noise' first (as Solderdude mentioned)?

So far I was never able to measure differences in the analog outputs, no matter what PS or battery was used.

 

[entrophy]

You misunderstood my post. Let me explain again: the goal with battery usage is to get rid of SMPS leakage current, and any capacitive coupling to the power grid (and earth/ground connections, of course).

I understood you perfectly fine, I was just wondering if the usage of a powerbank wouldn't introduce other issues that might not be obvious immediately.

Anyway, I noticed I never confirmed it explicitly, but you were right, of course: the noise in my setup is indeed not audible when listening through the headphones, so it is indeed the active monitors by themselves that make the noise audible.

Today I received a Radial Ice Cube IC-1 balanced line isolator:

https://www.radialeng.com/product/icecube

Plugging it into the XLR chain from ADI-2 DAC to active monitor first did nothing, noise was unchanged, but engaging the ground lift on the IC-1 made the noise go away.

EDIT:

Doing a few more tests, and changing the position of the active monitors in the powerstrip, the noise actually came back, even with the line isolator and ground lift engaged, so that points to the power connection of the active monitor that's picking up the noise. I'll be attaching an UPS to try and isolate the issue.

 

[Veri]

So far I was never able to measure differences in the analog outputs, no matter what PS or battery was used.

=) as it should be. Thank you for confirming.

 

[Alan S]

CD input

You mean DC input, right? See, everyone needs edit function. My English is so poor that I edited my first post 3 times in RME User Rorum. But I will improve, as knowledge.

Noise might be less, but how to measure this without defining 'noise' first (as Solderdude mentioned)?

I have already read the manual earlier, and I know the impact of power supply noise is very indirect as the DAC performs secondary filter and re-regulation.
But everything has its limit, and I don't have much technical knowledge about power supply noise, so I try to describe my question in the most common language possible and paste a web link about this Meanwell power adapter.

So far I was never able to measure differences in the analog outputs, no matter what PS or battery was used.

No worries, only enjoyment, this is what music should be like.
Thanks a lot.

 

[MC_RME]

I understood you perfectly fine, I was just wondering if the usage of a powerbank wouldn't introduce other issues that might not be obvious immediately.

Not that I am aware of. I have a very old powerbank that is so terrible that the noise becomes audible with anything. Its ground line must be modulated a lot. But since I recommended an earlier XTPower for the first Babyface I did not see problematic behaviour anymore, circuits seem to have improved. I measured both the XTPower and the TalentCell, and their outputs are even a bit better than the PS ones - nothing to worry about.

 

[entrophy]

Not that I am aware of. I have a very old powerbank that is so terrible that the noise becomes audible with anything. Its ground line must be modulated a lot. But since I recommeded an earlier XTPower for the first Babyface I did not see problematic behaviour anymore, circuits seem to have improved. I measured both the XTPower and the TalentCell, and their outputs are even a bit better than the PS ones - nothing to worry about.

That sounds good, thanks. Will definitely check the XTPower out.

EDIT:

Did some more testing, starting with the most basic setup: my active monitor speaker attached to an UPS that's running off battery, with the mains plug physically detached. Turns out that the speaker was buzzing, which leds me to believe that these have a general issue with their onboard PSU being poorly made. And the ground loops in the overall system are then amplified in the PSU.

 

[ShiZo]

I have a similar story to yours entrophy, except I've never heard any ground loop noise on the rme adi 2dac.

 

[badboygolf16v]

Yes, if you need both voltages that seems to make sense. But the next question is: what do you want to achieve with the battery operation? If it's perfect audio nirvana then a combined solution might not work perfectly, and you would need two separated powerbanks, one 9V, one 12V. At least in my measurement applications using two devices from the same powerbank sometimes fails with noise showing up again.

I was thinking of the portability aspect.

I've bought a USB DC-DC 5V to 9V step-up converter which I can plug into the XTPower and so will be able to power both the ADI-2 and ESP 95/X.

Whether there will be noise issues, I will soon find out!

 

[mcgo]

Baby, it’s HOT in here...

BMR-C1 Forged Copper
CG 50mm x 20mm x 2 5V USB

Target acquired in 3.. 2.. 1..

 

[Tks]

@mcgo Are you going to actively cool the DAC or something?