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DaveH1

Comparison between PI2AES and Directstream-Bridge II as a Roon endpoint

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Posted (edited)

Hi all,

I decided to add a short review of a Pi HAT that I’ve been using for about a month. It’s performance in my study system was excellent and I decided to experiment and hook up the PI2AES to my Directstream DAC and compare its’ performance to the Bridge II in the Directstream just for fun.

 

Background

 

I recently purchased a PS Audio Stellar Gain Cell DAC for my study. It is connected to an Emotiva XPA-2 Gen 3 amp and Ascension 863 SRTLs.

 

I had tried to find a Directstream Junior within my budget to use as a bridge/DAC/Preamp, but unfortunately couldn’t. The cheapest second hand DS Junior I could find was about $1300 more than the Stellar Gain cost me at $2600.

 

I wanted a headless Roon endpoint attached to the Stellar Gain DAC, but had read some ambivalent commentary about the audible qualities of the USB input on the DAC.

 

I used to own a Wyred 4 Sound Music Server and DAC-2 and to my ears, I2S was the superior interface, but that server was plagued by audible noise eg you could hear the hard drive spinning up through the speakers. You could hear the 50Hz hum of the supplied SMPS and the lowered noise floor and eliminated EMI when I changed to a linear PSU.

 

So, since then I have my DIY Roon Server and other servers in the garage and try to keep potentially noisy components as far away as possible from my systems.

A couple of folks on the PS Audio forum had also commented that the I2S input was the best sounding to their ears across multiple (PS Audio) DACs and as a result, I went in search of a headless Roon endpoint that can act as an ethernet to I2S bridge.

 

As an aside, PS Audio are developing their own music repository called Octave. I assume they will produce some sort of streamer/bridge internally, or via USB or I2S to their DACs at some point? I think the Bridge III has been shelved with this in mind. PS Audio, as far as I’m aware, will not support Roon in the longer term, as they focus on their own platform.

 

Headless Roon endpoints using I2S outputs

 

There are a few options that I could find for an endpoint/bridge with I2S out, but many involved more than one box. Having wanted an all in one unit to begin with, I began to struggle to find anything that was just one extra box for less than $500.

 

In the first instance you could use a Music Server, headless PC with a Pink Faun PCI adaptor or something like a Raspberry Pi and connect it to any one of a number of Gustard, Singxer or Matrix SPDIF units which support I2S. In the case of PS Audio DACs, you would need to find a unit which supports LVDS/HDMI output, as opposed to TTL/RJ45 that you find in some units (or face the issue of getting a converter board or cable).

 

Another two-box solution would be to use a Sonore microRendu and connect it to an ultraDigital.

 

Other more complete single box options are a Metrum Acoustics Ambre or something like a Sonore Rendu (now discontinued), but the prices for these items was approaching the cost of the Stellar Gain and well in excess of a 2nd hand DS Junior. I found a thread online where Sonore had commented that they’d abandoned the Rendu, due to lack of sales.

 

Finally, you could use a quiet server like the Antipodes and use their P2 to gain an I2S output, but we’re starting to look at big dollars for something that might not be audible or only marginally better than USB, in a small study system?

 

By chance I came across the PI2AES – Pro Audio Shield, on the PS Audio forums and decided to buy one to play around with. They’re designed by an enthusiast engineering-type guy called Michael Kelly at Pi 2 Design, who’s active on the superbestaudiofriends forum. I don’t know if the PI2AES is a hobby for him or a money making enterprise?

 

http://www.pi2design.com/store/p19/PI2AES_-_PRO_AUDIO_SHIELD.html

 

IMG20200102153148.jpg.4dd10cbb863062e708ecd187791249ad.jpgIMG20200102153129.jpg.4c0dfefce1446fa4e7a57a65501c7fc7.jpgIMG20191201080223.jpg.bd0ce51e866d4b9ed0d4baddce8b176b.jpgIMG20191130181604.jpg.99495e0393b66eda8b864e78132e99f8.jpgIMG20191130181503.jpg.ada7a3b12c104fa89a1e46ffc27a5ff7.jpgIMG20191130181340.jpg.22376d5dbd6dc700d0ef8cd1f6fe2f9e.jpg

As you can see, you buy a Raspberry Pi yourself and the HAT from Pi 2 Design. The PI2AES is like other Pi HATs and comes with some standoffs to mount correctly and I purchased an acrylic case from the manufacturer for it.

 

I bought a Pi 3 and loaded Ropiee to create a Roon end point. You select Hifiberry Digi + as your output in Ropiee.

Costs were as follows (inclusive of shipping):

  •         Pi 3 - $65.
  •         PI2AES - $272AU ($149 + shipping and tax = $186USD) shipped.
  •        Micro SD 16GB card - $9.
  •        Wyred 4 Sound I2S/HDMI 0.5m cable – already owned by me and cost around $300 at the time. Now $199USD, but you do see them on special from time to time.
  •        Gieseler 24Vdc, 2A linear PSU – purchased 2nd hand for $244. Needs a 2.5 x 5.5mm DC barrel.

 

So sans HDMI cable, I ended up being out of pocket around $580. The manufacturer sells/recommends a Meanwell SMPS that is 24Vdc at 1.67A for $30USD (sans shipping/tax). I’m sure you could pick up the Meanwell PSU online locally and there are many HDMI cables that would be similarly engineered for less money too, but it’d be fair to say it’s going to cost you at least $400AUD to put together from scratch.

 

Listening tests with Stellar Gain Cell DAC

 

My PC is about 5m around some bookshelves to the DAC, so I run optical straight from the PC’s mainboard and then I ran the HDMI cable from the PI2AES to the Stellar Gain DAC.

 

Initially, I synced my PC and the PI2AES and then A-B’d the two endpoints by switching inputs. I volume matched some test tones with a Radioshack SPL meter to make sure the comparison was as close as possible.

 

I wasn’t really surprised that the PI2AES sounded better than my PC with an HDD, large fans and PSU.

 

What did surprise me was just how much better it sounded! After a run-in period of probably 10 hours where the PI2AES sounded a bit shrill, it then settled in and delivered this incredible holographic soundstage in my little study. Mainly, I had wanted something just functional that I could sync with the system in the living room, but listening to this little Pi put a huge stupid grin on my face.

 

I then moved it to the living and connected it into one of the I2S inputs on my Directstream DAC (running Windom) to compare it with the Bridge II.

 

Listening tests with Directstream DAC (Bridge II v PI2AES/I2S)

 

My living room system is: Shunyata Hydra Power conditioner, Octave HP700 Preamp, Bakoon 11R amp, Zu Soul Superflys, Krispy power cables. Generic shielded Cat 7 cable on the Directstream/Bridge II and generic unshielded Cat 6 cable on the PI2AES. Sota Millenia turntable. Kuzma 4 Point, Lyra Etna.

IMG20200102153413.jpg.a45e3e93bcb307ab9a81c15ff0ef3e60.jpg

Here things are much closer. In fact, I couldn’t be absolutely confident I could differentiate the Bridge II from the PI2AES in a blind A-B test for many passages of music. In some sections of music, the differences were pretty clear. Not bad or good, or better even. Just different.

 

We started listening with A Million Dream’s from the Greatest Showman Soundtrack, followed by Zedd’s Addicted to Memory, Avicii’s Wake Me Up, P!nk/Chris Stapleton’s Love Me Anyway, Dreaming of the Crash from the Interstellar Soundtrack and finally 42 and Wild Heart from Mumford and Sons’ album, Delta and then we just kept listening for a couple of hours as we sometimes do…but to the PI2AES!

 

What I would say is that the PI2AES has better detail retrieval and accuracy than the Bridge II, particularly with keyboard instruments and strings. The DS DAC/Bridge II as many of you would know, delivers a wonderful soundstage with instruments nicely imaged across the living room. It’s a lovely, warm and comforting sound. It’s effortless and not fatiguing.

 

If there was a difference, the PI2AES might have a slight digital presence that could be off-putting to some. After all, many of us enjoy PS Audio products because we have a love of vinyl playback and their products’ bring us closer to hearing that sound. As the afternoon wore on though, we stayed on the PI2AES input and didn’t change back to the Bridge II. That I thought was a statement in itself.

 

Final thoughts from my wife

 

My wife thinks my enjoyment of Hifi is indeed an illness. I was reading Stereonet the other day and she wandered past the door and asked me what I was doing at the computer? I replied that I was looking at audio porn. She replied that she wished I would watch porn instead, as it would be a whole lot cheaper than a Hifi addiction!

 

But my wife was sitting with me whilst I A-B’d the PI2AES. She had no idea what each bridge was worth. She had no idea which endpoint she was listening to at which point in time because she doesn’t know which bit does what. Indeed, she has no idea of the relative cost of any product.

 

What did surprise me was that she could fairly reliably pick the PI2AES from the Bridge II. She preferred it too on the basis that it sounded more realistic to her.

 

Conclusions

 

Pros

 

  •         For approximately 40-50% of the cost of the Bridge II, the PI2AES performs equally to the Bridge II.
  •         It can be used with other DACs with HDMI/I2S in, just remember to check if your DAC manufacturer’s pin out matched the PI2AES.
  •         Headless Roon endpoint using Ropiee or any one of a bunch of RAAT capable operating systems.
  •          Supplied from the manufacturer in USA.
  •         Excellent support from the manufacturer.
  •         Can utilize the I2S input on your DAC for a Roon endpoint if/when PS Audio switch to their Octave platform.

Cons

 

  •         DIY, although if you can burn a DVD on your computer and can follow instructions, the DIY part is very straightforward.
  •         A separate box, a separate PSU and separate cables required.
  •         A digital presence that might not appeal to some. However, for those who like their music accurate, with a detailed soundstage and excellent imaging, you may well prefer the PI2AES over the Bridge II.
Edited by DaveH1
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7 hours ago, DaveH1 said:

PI2AES – Pro Audio Shield

Great write up DaveH1

 

Have you tried the PI2AES’s TOSlink optical output?

 

If you do try optical, as Ted Smith recommends disconnect the other inputs of the DirectStream DAC when listening otherwise you don’t get the key benefit, optical’s perfect RF isolation.

 

 

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No, I didn't, but will go back and try this on the Stellar Gain.

 

I'd be reluctant to remove the Bridge II on my Directstream though, just to test this.

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Great write-up, thanks heaps. What’s the maximum rate supported by the Pi in this configuration? I’m currently limited to 192kHz PCM or DoP64 in my setup and accessing the higher speeds would be the main reason I’d consider switching to an I2S input. 

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Posted (edited)
12 hours ago, DaveH1 said:

I'd be reluctant to remove the Bridge II on my Directstream though, just to test this.

Ted's recommendation when testing different inputs is just to disconnect other cables.

 

I did read somewhere that the Bridge2 card still consumes power (and produces noise) even if ethernet cable is unplugged and using a different input - but I agree unplugging the Bridge2 card is a pain, as you said,

 

So (if you get a chance) just unplug the ethernet cable when testing optical (especially if using a shielded ethernet cable which can pass ground loops via shield).

Edited by rand129678
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Just a quick clarification, the board to select is "Hifiberry Digi + Pro". Eventually  the music players will have our board listed, but it is fully compatible with the Hifiberry board.

 

Michael (Owner of Pi 2 Design)

 

P.S. Thanks for the great write-up, and yes this is a money making venture, eventually!

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On 03/01/2020 at 8:25 PM, rand129678 said:

Ted's recommendation when testing different inputs is just to disconnect other cables.

 

I did read somewhere that the Bridge2 card still consumes power (and produces noise) even if ethernet cable is unplugged and using a different input - but I agree unplugging the Bridge2 card is a pain, as you said,

 

So (if you get a chance) just unplug the ethernet cable when testing optical (especially if using a shielded ethernet cable which can pass ground loops via shield).

Sorry have been catching up with work over the last few weeks and have just tested your suggestion over the weekend.

 

My feeling is that optical is equivalent to the Bridge II. I think the I2S output probably just edges both out in terms of clarity/accuracy. But in a double blind test I'm not sure I could tell the difference between the two outputs?

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On 03/01/2020 at 10:35 AM, kdoot said:

Great write-up, thanks heaps. What’s the maximum rate supported by the Pi in this configuration? I’m currently limited to 192kHz PCM or DoP64 in my setup and accessing the higher speeds would be the main reason I’d consider switching to an I2S input. 

Best to check with Michael Kelly. I don't know the answer and don't own anything more than 24/192 to test.

Manual seems to suggest 24/192: http://www.pi2design.com/pi2aes.html.

Cheers, Dave.

Edited by DaveH1
Added link to manual.

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