Linear PSU for Raspberry Pi 3, which one? Confused.

[drtebi]

I am having trouble to figure out which PSU (kit or assembled) to choose for my raspberry-based network transport project.

The plan so far is:

- Filtered Power Inlet module with fuse
- R-Core transformer with two 110V primaries
- Linear PSU
- Powerblock
- Raspberry Pi 3 with Allo DigiOne
- S/PDIF output jack
- Ethernet input jack

The PSU is where I am stuck. I have searched all over the internet for a PSU kit with instructions etc., and initially settled on building the sigma 11 PSU from amb.org, but now the site is down!

There appear to be suitable Chinese PSUs offered on eBay, but with vague or confusing instructions (if there are any).

I am looking for something like the PSU-2448 from FiveFish Audio but that particular one is rather for mic-preamps.

I am new to this, but from what I have learned, this appears to be what I need:

-> A transformer with two 110V primaries and a secondary of about 6V output
I want to be able to switch it to 220V later on, so two 110V primaries running either in series or parallel should work for that(?).

-> A low noise PSU that can handle at least 1.5 amps.
The raspberry in the proposed configuration shouldn't need more than ~700mA, although I don't know the power consumption of the Allo DigiOne; but 1.5A would be safe, also considering the occasional USB connection to a keyboard/mouse etc.

I would really appreciate any pointers. You can also tell me that I am completely wrong with my approach... convince me of something better 🙂

 

[Mark Johnson]

If the raspberry pi 3 is a digital circuit board, the benefits of supplying its DC power from a linear PSU, will be small.

 

[jplesset]

Rasberry Pi is indeed digital. It's a small computer. Unless you end up with an extremely noisy power supply, liner is not a requirement for excellent sound.

 

[drtebi]

If the raspberry pi 3 is a digital circuit board, the benefits of supplying its DC power from a linear PSU, will be small.

Rasberry Pi is indeed digital. It's a small computer. Unless you end up with an extremely noisy power supply, liner is not a requirement for excellent sound.

I have heard that a few times, but I have also heard the opposite a few times, so I guess it is debatable.

So let's just say I want to do it anyway... any suggestions on a good kit?

 

[Andrewbee]

May I suggest you read this article, based on measurements and not "subjective science"

If you still want a linear supply after that then I would suggest one of those USB power banks - a big battery, maybe one of the 20K mAh units. Whats more linear than a battery afterall.

Archimago's Musings: MEASUREMENTS: Raspberry Pi 3 as USB Audio Streamer (with recommended CRAAP config & TIDAL/MQA arrives)


Andrew

 

[drtebi]

May I suggest you read this article, based on measurements and not "subjective science"

If you still want a linear supply after that then I would suggest one of those USB power banks - a big battery, maybe one of the 20K mAh units. Whats more linear than a battery afterall.

Archimago's Musings: MEASUREMENTS: Raspberry Pi 3 as USB Audio Streamer (with recommended CRAAP config & TIDAL/MQA arrives)


Andrew

But the article clearly says:

It just sounds much better now that I have tweaked the parameters. Bass is deeper. Treble even more trebly. Soundstage goes back a mile with 360° envelopment.
​

!!

OK, just kidding. Although the test was not between a switching and linear power supply, I must assume that the difference of these two is rather inaudible, and I may just kill the idea of a linear power supply.

Well then, any other suggestions to get the best out of a raspberry pi 3 based transport?

Should I also assume that the difference between USB -> DAC vs. Allo DigiOne S/PDIF -> DAC should be indistinguishable? What is the advantage of the Allo DigiOne then? Longer cables?

 

[Andrewbee]

In a nutshell, a digi output HAT gives you a digital output which you then plug into your DAC. Think of the Digi HAT and RPI3 as a transport. S/PDIF is the recommended connection vs e.g. USB (quieter).

The other version is as a DAC where you have a DAC HAT as the output e.g. Hifiberry DAC + on the RPI so you now have a DAC output.

So for instance in my particular situation I have a digital amp so only need a transport. I use the optical output from my CD player straight into the optical input of my digital amp, no DAC needed but next for me is a second RPI3 and a DIGi HAT so I can use my HDD with FLAC files on the digital amp.

For my analogue amps I use a HDD with FLAC files connected to a RPI3 with a Hifiberry DAC + Pro so that would be like a transport and DAC.

Hope that helps.

Andrew

 

[drtebi]

In a nutshell, a digi output HAT gives you a digital output which you then plug into your DAC. Think of the Digi HAT and RPI3 as a transport. S/PDIF is the recommended connection vs e.g. USB (quieter).

The other version is as a DAC where you have a DAC HAT as the output e.g. Hifiberry DAC + on the RPI so you now have a DAC output.

So for instance in my particular situation I have a digital amp so only need a transport. I use the optical output from my CD player straight into the optical input of my digital amp, no DAC needed but next for me is a second RPI3 and a DIGi HAT so I can use my HDD with FLAC files on the digital amp.

For my analogue amps I use a HDD with FLAC files connected to a RPI3 with a Hifiberry DAC + Pro so that would be like a transport and DAC.

Hope that helps.

Andrew

Thanks Andrew. I think I have understood that much already. I do have a DAC that can accept S/PDIF as well as USB. It's a pretty good DAC (RME ADI-2 Pro), so I wanted to just use the Raspberry as a transport only (e.g. no DAC within the Raspberry).

But since I could use either

1) Raspberry USB -> external DAC, or
2) Raspberry with Allo DigiOne S/PDIF -> external DAC
​

I was wondering if there would be any advantage in 2).

The Allo DigiOne is very similar to the Digi HAT by the way.

 

[Andrewbee]

IMO, generally its 6 of one, half dozen of the other. They are all pretty similar, more alike than different. I think once you get to the e.g Hifiberry DAC + Pro stage where you have a transformer for isolation and separate clocks for jitter reduction (another somewhat controversial subject) I don't see it getting much better. There is a the ability to power the analog section separately which you were contemplating, I really don't see the necessity, its really all "fluff". If the power to the RPI3 is "clean" (tests show it is) why power the DAC or part of it separately unless to satisfy the audiophile tweakers addiction.

Even switching power supplies have their fans, a switching frequency for a linear power supply is 50 / 60 cycles depending where in the world you are vs a switching power supply which could be as much as 1MHz or more, which one would likely be more audible? If properly done none would be. The switching power supply however will be smaller, cooler and cheaper.

If its "Bit Perfect" then it can't get any better, different sounding maybe but technically its as good as it gets.

Once here its like seasoning a meal, some may like a lot of Garlic and others not, it does not make it better or worse, just different.

 

[drtebi]

Once here its like seasoning a meal, some may like a lot of Garlic and others not, it does not make it better or worse, just different.

You clearly haven't tried my cooking yet 😉

One thing just occurred to me: The external DAC I am using is actually also my Pre-Amp. So it would make little sense to use a DAC on the Raspberry, go into the external DAC where the analog signal is again converted to digital etc. In other words, I would have unnecessary D/A - A/D - D/A conversion.

Well, I think I will just get the Raspberry for now, and then play around with it...

 

[linuxfan]

The plan so far is:
...
- Raspberry Pi 3 with Allo DigiOne
- S/PDIF output jack

The external DAC I am using is actually also my Pre-Amp
...
I would have unnecessary D/A - A/D - D/A conversion.

That's incorrect. You need to understand that the DigiOne is not a DAC - it simply converts the raw digital I2S audio signal coming out of the rPi into s/pdif - that's a conversion from one digital transport protocol to another - the signal remains in the digital domain.
It's actually quite an expensive converter - which raises the question of whether your DAC is of high enough quality to make this a sensible choice?

Can you tell us what your DAC is?

The purchase of a rPi gives you the opportunity to review your entire signal path, and system configuration. A high quality rPi hat-DAC such as the ALLO Boss costs less than the s/pdif converter, and is likely to outperform commercial standalone DAC's costing up to about $500.

So again, what's your existing DAC?

 

[Bigun]

A high quality rPi hat-DAC such as the ALLO Boss costs less than the s/pdif converter, and is likely to outperform commercial standalone DAC's costing up to about $500.

what would be needed to get above $500 in equivalent quality (power supply and DAC HAT) using an rpi ?

 

[linuxfan]

Which brings us to the subject of power supplies. If your rPi has a hat-DAC which shares common power supply with the rPi, then you are likely to benefit from using a good quality linear power supply - from the point of view of the DAC supply.
Of course it's possible with some hat-DACs to provide separate power input, that's a whole other story.

Does the rPi, itself, benefit from a linear supply? That's long been a contentious subject.
The respected electronics designer John Swenson claimed that the SqueezeBox Touch (a technical predecessor of the rPi) sounded better when fed from a well-filtered LT1084-based supply. He speculated that the SQ improvement might have simply been due to this supply NOT polluting analogue audio grounds, as the standard SMPS unit does.

If you want to try a linear supply, here are some options;

GlassWare LD1085 LV-Regulator $31
LV-Regulator

a more basic LM1085 regulator
LV30 Variable Voltage Regulator (2A) Kit_Power Supply Kit_Analog Metric - DIY Audio Kit Developer

jean-paul's LT1764 regulator with chokes -
Squeezebox Touch PSU
Building the SBT PSU

Raspberry PI PSU with TPS7A8300 (linear regulator fed by SMPS)
Raspberry PI PSU with TPS7A8300 5V 2A

or a well filtered SMPS - iFi iPower
https://ifi-audio.com/portfolio-view/accessory-ipower/

 

[Bigun]

I'd enjoy the challenge of building my own supply, or even multiple supplies for the different voltages. I'm not sure how much benefit having separate supplies for the 5V and 3.3V etc. would bring but once you start down the DIY path it's not much additional effort. Interesting comment from Swenson, it makes some sense.

Do you have a favourite hat-DAC for this purpose ?

 

[linuxfan]

what would be needed to get above $500 in equivalent quality (power supply and DAC HAT) using an rpi ?

Well don't hold me to $500 as a strict figure, but I think if you want to go true high end, you need to move beyond a hat-DAC to external DAC.
In terms of commercial DACs, I'm thinking of the entry level Denafrips DAC, or the entry level Resonessence Labs DAC - both using USB input - because the I2S output of the rPi is jittery by high-end standards ...
but of course another option is to add a reclocker to the rPi's I2S outputs, in order to feed an external DAC.

DIY DACs? TwistedPear Buffalo, Mirand Audio AK4490 ...

 

[linuxfan]

Do you have a favourite hat-DAC for this purpose ?

I'm not in the rPi camp at all - I have a BeagleBone Black, with external clock interface board by TwistedPear. And yes, I use a linear supply for the BBB, but I don't insist this is essential.

 

[Bigun]

Thanks ! I don't know much at all about DACs so it's helpful to get a chance to ask some questions even if a bit OT 😀

 

[drtebi]

That's incorrect. You need to understand that the DigiOne is not a DAC - it simply converts the raw digital I2S audio signal coming out of the rPi into s/pdif - that's a conversion from one digital transport protocol to another - the signal remains in the digital domain.

I do understand that. It was suggested in the beginning of this thread that I could use a DAC HAT for the raspberry. If I would do that, then I would have the unnecessary D/A, A/D, D/A conversion.

It's actually quite an expensive converter - which raises the question of whether your DAC is of high enough quality to make this a sensible choice?

Can you tell us what your DAC is?

I believe it's quite a good one, you can judge for yourself:
RME ADI-2 Pro

Thank you for the power supply links. Just like Bigun, I do like the idea and challenge to build my own PSU. It also just feels right to have a PSU in there, as opposed to some SMPS lying on the floor, dragging with you if you want to use the player elsewhere... yes, it's more esthetics and pride than sense, but why not if it doesn't cost that much...

 

[linuxfan]

Yep that looks like a good DAC, so the ALLO DigiOne is certainly a good choice to connect to the rPi.

But let me delve further - the ADI-2 Pro is an audio production device - is it also being used in a home recording setup?
You might be better off buying the ALLO Boss, then keep your music playback system completely separate from your recording setup, for the sake of convenience? Just putting the idea out there.

 

[drtebi]

I already own the ADI-2 Pro. I am using it in my music playback system, not professionally.

I bought it for many reasons... it's a long story. However, one reason in particular is the parametric EQ, which is great for adjusting the bass roll-off of open baffle speakers. I also like it for A/D conversion, to record vinyl (after running the turntable output through a phono pre-amp).

The ALLO Boss sounds good as well, but since I already have the ADI-2 Pro, the Allo DigiOne makes more sense.

What's your take on adding a linear power supply to this setup (rPi + Allo DigiOne)?