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Linear PSU for Raspberry Pi 3, which one? Confused.
Linear PSU for Raspberry Pi 3, which one? Confused.
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Old 20th October 2017, 01:24 AM   #11
linuxfan is offline linuxfan  Australia
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Quote:
Originally Posted by drtebi View Post
The plan so far is:
...
- Raspberry Pi 3 with Allo DigiOne
- S/PDIF output jack
Quote:
Originally Posted by drtebi View Post
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?
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Old 20th October 2017, 01:28 AM   #12
Bigun is offline Bigun  Canada
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Linear PSU for Raspberry Pi 3, which one? Confused.
Quote:
Originally Posted by linuxfan View Post
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 ?
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Old 20th October 2017, 01:29 AM   #13
linuxfan is offline linuxfan  Australia
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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/
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Old 20th October 2017, 01:35 AM   #14
Bigun is offline Bigun  Canada
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Linear PSU for Raspberry Pi 3, which one? Confused.
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 ?
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Old 20th October 2017, 01:56 AM   #15
linuxfan is offline linuxfan  Australia
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Quote:
Originally Posted by Bigun View Post
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 ...
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Old 20th October 2017, 01:57 AM   #16
linuxfan is offline linuxfan  Australia
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Quote:
Originally Posted by Bigun View Post
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.
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Old 20th October 2017, 02:02 AM   #17
Bigun is offline Bigun  Canada
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Linear PSU for Raspberry Pi 3, which one? Confused.
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
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Old 20th October 2017, 03:30 AM   #18
drtebi is offline drtebi  United States
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Quote:
Originally Posted by linuxfan View Post
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.

Quote:
Originally Posted by linuxfan View Post
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...
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Old 20th October 2017, 08:03 AM   #19
linuxfan is offline linuxfan  Australia
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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.
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Old 20th October 2017, 08:17 AM   #20
drtebi is offline drtebi  United States
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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)?
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