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RPi-4B and Power ??

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Posted on January 13, 2021 at 11:42:54
tvr2500m
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Location: Boston
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...and maybe signal clean up, but first, power.

I'm pretty dug into the RPi-4B streamer thing now, and still learning. Tried Volumio and VitOS. Running Roon/RoPieee and also piCorePlayer/LMS/SL (thanks, again, Cut-Throat for your help on getting this going). It's all humming along well enough.

I have a question about what's going in and out of the RPi-4B, both for power and signal. I'm especially and particularly curious about power in and out of the RPi for those devices that run only off USB power (and signal) supplied by the RPi. I have several devices that do this - the Meridian Explorer2, the Resonessence Herus DSD DXD and Concero HP DSD DXD.

I'm currently feeding my RPis with Canakit wallwart RPi supplies and I'm supplying these DAC/amp devices with the USB power out of the RPi.

On the power topic only, I'd like to hear people's experience of feeding the RPi a tidier power source, and also then tidying up the power out of the RPi feeding the DAC/amps.

For all devices fed by the RPi, I'd like to hear people's experience of using something that also cleans up the RPi output signal.

I know there are lots of ways to address all this - HATs, external devices like the ifi micro iUSB3.0, and higher-spec'ed power supplies.

Feedback appreciated.

Thanks.

 

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Here is what I do ................., posted on January 13, 2021 at 12:03:18
Cut-Throat
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For my Main (Critical) Listening System, I use a Linear Power Supply. I got mine from Swagman Labs.
http://www.swagmanlab.com/Product_PSU?product_id=631 -- I have a couple of these. The Base Model costs around $160 -- The 'Signature' Model is around $300....

I assume you are using the USB output into a DAC? -- If so, I would not worry about 'Cleaning Anything Up'... I would however advise against powering a USB Drive from the Rpi (For Critical and your Main Listening System). I Would get a NAS for this purpose.

If you want to use a Coax Output from your RPi, I would look at the Allo Digione 'Hat'

I use both the USB Output and the Digione Coax Output into my DAC. In fact I have both hooked to my Same DAC on my main system, so it is easy to switch back and forth. The USB output can play DSD, while the Digione Coax output cannot.






 

Ditto C-Ts advice, posted on January 13, 2021 at 14:44:24
E-Stat
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Avoid SMPS as they sacrifice resolution.

I use battery or ultra capacitor based solutions with mine.

 

Fit to RPi4, posted on January 13, 2021 at 18:27:33
valvesonly
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Posts: 748
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I don't see the Pi USB connector in there though the 5V 3A works.

How much did this improve the stock powersupply. Currently I use the Argon 5.25V 3.5 Amp so I can drive the USB3 for a SSD boot and run LMS with the music Library. Seems as good as ethernet from a full Win 10 PC harddrive but I have not had recent time for critical listening.

.
must..NOT..resist..."upgraditis"

 

RE: RPi-4B and Power ??, posted on January 14, 2021 at 01:31:12
soundchekk
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Posts: 2187
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Any of the advise you've been given so far I consider highly questionable.

If you experience "hum" in the system it's usually bad grounding connection
or a broken device.
Check your cables and connectors and also introduce a proper grounding scheme,
such as a star grounding scheme. Keep your cables short.

Now there keeps the myth "SMPS is bad", "Linear is good" and "battery is better"
nonsense floating around. Well underlined by the other responses to this thread.

There are characteristics which clearly define the quality of a power supply, such as

* current capability
* ripple (periodic) and
* noise (random),
* transient response,
* impedance,
* accuracy,
* load regulation,
* temperature stability,
* and more

These characteristics will define the quality of a power supply.

You can achieve top quality results with any type of power supplies.
What matters is the implementation first of all. Usually designing
a high quality SMPS is more complex then designing a Linear supply though.
And that's the key factor. Complex = high cost and effort. That's why you'll find many low Q SMPS out there and SMPSes got a bad rep.


However. There's no reason why a well done (having a good spec according to above) SPMS with a
nice buffer on it's output shouldn't do as good or better as a high Q (according to above spec) linear supply or a high Q battery supply.

Again, what matters are the specs.

Unfortunately manufacturers do not tell you much about it.
Even if the "Noise" spec is shown, it won't tell you much.
Often you'll find noise specs shown for a 0-20kHz range.
That's simply not enough. Higher frequency noise can also very well impact attached devices.
And it's a noise spec produced in a lab environment. You wouldn't know how such a device would work in a real world setup. How much noise it generates on the mains etc in your home environment.


Manufacturers hiding these and most quality parameters IMO for a reason.
Not many people demand them! I once did demand them for the Allo devices.
The answer was like. "We provide what others are providing". All I can tell I didn't make friends by asking for it.

E.g. attaching a 5 foot cable and some el-cheapo connectors plus adapters to a PS will definitely kill every "transient response" characteristic.
That's IMO why manufacturers simply avoid showing it. iFi and Allo belong of course to the few companies who talk about the subject at all.

You might want to have look at quality Lab Power supply specs. Usually these offer more related info. I'd expect high quality (audio) power supply manufacturers to at least extend their datasheets on that lab supply level.

I also had to taken my choice, even without having plenty of specs around.


I've been running my RPis with modified iPower SMPS for years. My RPi 4 server with 2 USB SSDs attached still runs stable with one of these. This doesn't mean that a stable and rather clean $15 SMPS wouldn't be able do the same job.

Still. Nowadays I'd buy an Allo Nirvana SMPS. For that purpose. I can keep the cable short. That keeps the impedance low and betters the transient response all at a reasonable price tag.

Now the streamer.

I'd try to keep the RPi and audio interface PS separated. I'd use two Allo Nirvanas or one Allo Shanti - the Shanti only in my modded version (shorter cables, DC relays) though.



I did have iFi and other USB filters around. I still use one on my Khadas Toneboard.
On modern DACs like the D90 - according to Audio Science Review - these filters do not show any effect on their measurement equipment. This of course could differ from DAC 2 DAC.

The Allo devices also offer a nice starground point to cope with groundloop issues.

Bottom line.


Even this response can not be satisfactory. I know. It's because there's
simply not the one and only solution.



Good luck on your journey.

Enjoy.

 

RE: Fit to RPi4, posted on January 14, 2021 at 03:59:13
Cut-Throat
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Location: Minneapolis - St.Paul Area
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"I don't see the Pi USB connector in there though the 5V 3A works. "

The will make the cable any way you want. Just specify that you want a Micro-USB Cable to fit into the Model 4 Raspberry Pi.. I've got Cables that Fit Model 3 and 4 as well as the old Squeezebox Touch.






 

RE: RPi-4B and Power ??, posted on January 14, 2021 at 07:16:17
E-Stat
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Nowadays I'd buy an Allo Nirvana SMPS.

Allo disagrees with your love of switchers unless you have a restricted budget.

I'd go for a Shanti. ;)

"As explained, Shanti is not only shining because of the ultra-low differential noise and common mode noise, but because of incredible low impedance / deep reservoir of electrons at the output of the PSU."

 

RE: RPi-4B and Power ??, posted on January 14, 2021 at 08:23:21
soundchekk
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Joined: July 11, 2007
I own and run a Shanti - I think I mentioned more than once.

Allo doesn't disagree. They "hear" a minor difference. That's how I recall it. Let's not talk under what conditions.

They want to sell the product that very well fits the picture of the crazy audio crowd out there. And that's gotta be a linear supply.

Top high end audio gear manufacturers use SMPSs since years. That linear thing is a myth.

Once more. What matters is the implementation.


If Allo would have attached the same supercaps to the Nirvana output, which wasn't done, and I guess wasn't done on purpose, we wouldn't have this discussion. That's simply been a marketing decision. They needed to stay in the iPower ballpark.

And the Shantis "incredible low impedance" - a nice try. Have you seen
any transient response measurements?

Yep. Supercaps can a have quite a low ESR. At the soldering pins. But what's left of it after a 5 foot cable and some el-cheapo connectors and adapters. I never received an answer on that question.

The first thing I've done, was replacing and shortening the Shanti cables and of course getting rid of the plugs.

Enjoy.

 

RE: RPi-4B and Power ??, posted on January 14, 2021 at 08:29:43
E-Stat
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Top high end audio gear manufacturers use SMPSs since years

Perhaps to you. I'm always amused when folks play the role of apologist to a manufacturer's product decisions. I hear the same silly explanation for speakers having bi-wiring posts. :)

Have you seen any transient response measurements?

I couldn't care less about simplistic metrics. What I hear is far more important. As for DC cables, both of mine are one foot and use low inductance star quad construction. What I hear is better dynamics, especially at the PP end of the scale.

 

RE: RPi-4B and Power ??, posted on January 14, 2021 at 09:11:09
soundchekk
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Posts: 2187
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Yep. "You couldn't care less."

Sounds pretty ignorant to me.

You're fighting my arguments about lower impedance and better transient response as objective, thus measurable, quality parameters for power supplies and then you're telling us, that you actually did lower the impedance and improve the transient response in your setup by replacing the cable.

...obviously without realizing what you're doing.

Watch your attitude!

Enjoy.


 

I greatly prefer listening to music, posted on January 14, 2021 at 09:17:00
E-Stat
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to reading charts. There are few metrics with direct correlation to what we hear.

To each his own. Even grumps like you. ;)

 

Cable Length ? .................., posted on January 14, 2021 at 10:09:07
Cut-Throat
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You mentioned a 5 ft. Cable Length. In your opinion, what is the longest cable you'd be comfortable with?

Also would the distance between the Power Supply and the Raspberry Pi matter at all. In other words, could you place the Raspberry Pi on top of a Power Supply?






 

RE: RPi-4B and Power ??, posted on January 14, 2021 at 14:20:36
zacster
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Posts: 1668
Location: NYC
Joined: November 22, 2003
I use an Anker phone charging battery to power my Pi and also my Topping E30 since it has 2 USB ports. I then connect the Pi to the Topping with yet another USB cable that carries signal only.

I've tried using the stock SMPS supply with the Pi, and an iFi iPower unit. With the iFi, I bought it after I had been using the battery for a while and my first reaction was it ruined the sound. I used it for a few days and then switched back to the battery. The reason for trying the iFi was that I wanted to automate the on/off sequence using Alexa. The battery would cut power to the Pi when it received power, which was good in that it would charge itself that way, but when power to the battery was cut it did not automatically power up the Pi. I would need to push the side button to power up the Pi. Not a huge deal but I wanted to be able to control it from the couch. At the time I did this I used an Allo Boss hat on a Pi3. At some point I went back to the iFi again and said I could just live with it, until I decided yet again I couldn't and switched back to battery. And guess what? It really did just sound better with the battery.

When I bought the E30 the battery came in handy in that it had 2 ports so I could supply both the E30 and the Pi from the same pack. And by default the E30 separates the power from the signal, which is nice. I never tried an SMPS on the E30 though. I even have a linear supply that it came with (both used) that I never tried. I switched to a Pi4 also somewhere during this time.

As for the Pi3/Boss/iFi, my daughter now has it all and couldn't care less about the subtle sound difference. She just wanted to stream music from her phone, plus it is a direct plugin to the TV.

 

RE: RPi-4B and Power ?? Buck-Boost converter IC, posted on January 15, 2021 at 06:57:33
AbeCollins
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I have the iFi iPower and it works about as well as my $6 wall wart smps from Amazon ;-)

Inmate E-Stat reports that his Raspberry Pi sounds better with an external USB battery.

The only reason I can think of that might support the improvement from a technical perspective is that the battery is isolated from the AC mains during operation. Otherwise, USB battery packs are essentially DC-DC converters (switching power supplies) in that the relatively low 3.6v from the Li-Ion battery needs to be boosted to 5vdc. If there are 3.6v batteries in series in the battery pack, the higher voltage needs to be bucked down to 5vdc.

As for iFi's marketing department, they really know how to spin tech ;-)

iFi ad from a couple years back:
I think they pulled the ad cuz too many folks laughed at them!

Come on iFi, it's just a freak'n wall wart!



 

usb y cable, posted on January 15, 2021 at 11:22:14
LtMandella
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Location: CA
Joined: May 27, 2019



For many of my devices that use a usb plug for power I use a "dual plug".

So two USB power sources are combined to one, or one supplemental and one integral with signal can be combined.







If art interprets our dreams, the computer executes them in the guise of programs!

 

RE: RPi-4B and Power ?? Buck-Boost converter IC, posted on January 15, 2021 at 17:20:22
zacster
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Posts: 1668
Location: NYC
Joined: November 22, 2003
Doesn't surprise me. This is yet another example of an internet company that relies on positive reviews that are suspect. I also have an iFi DAC that I still use but not in a critical environment. It sounds OK but it isn't great and I have trouble with charging. I'm still not sure which way to turn it on to get it to charge vs. just play off power.

 

RE: RPi-4B and Power ??, posted on January 16, 2021 at 01:45:24
fmak
Audiophile

Posts: 12992
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Add power supply bandwidth. Most supplies have an upper frequency limit beyond which 'regulation' is ineffective. Typically, IC regulators are poorer than solid state high quality units.

 

transient response, posted on January 16, 2021 at 01:47:45
fmak
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very important

 

RE: RPi-4B and Power ??, posted on January 16, 2021 at 05:51:00
soundchekk
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Transient response somewhat relates to bandwidth.

https://www.electronicdesign.com/technologies/test-measurement/article/21805656/simple-transientresponse-measurement-determines-powersupply-bandwidth

I'd be happy to see any of these in a PS datasheet.

 

On a system level, yes, posted on January 16, 2021 at 06:07:02
E-Stat
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there are many components which determine that.

Speakers having diaphragms with lower mass than the air around them is one important factor to me.

 

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