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Topic: Audio quality on SBCs like RPi (Read 14682 times) previous topic - next topic
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Audio quality on SBCs like RPi

I am looking to expand my setup of playback devices for mpd and Logitech Media Server. (That's not the only intended use, I might want to have these devices interact with additional standards and protocols like Miracast or DLNA.)

I already have two Raspberry Pis (RPis). I use them in conjunction with external USB audio interfaces. It works fine, but those external DACs add to the cost as well as to the size of the device. I'm also aware that for some devices, internal add-on DACs exist, but you need to be able to solder for that.

To get to the point: there are now a gazillion of single-board computers (SBCs) which are potential candidate devices for my intended use. Raspberry Pi, ODroid, and Wandboard, just to name a few. Has anyone any experience with the analog outputs (mini-jack or RCA) on any of those? Or maybe even ran RMAA tests?

The sheer number of available SBC options confuses me. I hope information about the sound quality of various SBCs would help me narrow things down. I also think this information may be useful to other readers of this forum.

Audio quality on SBCs like RPi

Reply #1 –
The Pi is supposed to be terrible.  No idea about other devices, but I wouldn't be surprised if some of the newer device have more acceptable (if not great) output.

Audio quality on SBCs like RPi

Reply #2 –
Most of them support external USB DACs...when a RaspPi costs so little and if you're primarily using it for audio I don't think it's too much extra to spend

Audio quality on SBCs like RPi

Reply #4 –
Quote from: saratoga on
The Pi is supposed to be terrible.  No idea about other devices, but I wouldn't be surprised if some of the newer device have more acceptable (if not great) output.


Any links to back up this claim? I'd be interested in reading about it.

Audio quality on SBCs like RPi

Reply #5 –
Quote from: probedb on
Most of them support external USB DACs...when a RaspPi costs so little and if you're primarily using it for audio I don't think it's too much extra to spend

Yeah, it's not just the money. There are two more reasons. For one, it's nice to have a single small device which you can place/mount nicely. Things get more cluttered when you add an external USB DAC. Second, the USB ports on some of these devices are imperfect. They may provide little power so that a powered hub is required (more clutter). Or there's a small number of ports with limited bandwidth (such as on the RPi where the ethernet is connected to the SoC via USB). I think you're a bit more likely to run into driver or performance issues than on a fully-fledged PC.

Quote from: Roseval on
Maybe this one: http://www.element14.com/community/communi...ries/wolfson_pi

It's a nice suggestion, thanks. No soldering required. I'm wondering if this will fit into the cases I have.. The price of this is not bad. It's still 25 EUR, though, which is almost the price differential between the RPi and more powerful SBCs. So I think my original question is still valid.

Quote from: yourlord on
Any links to back up this claim? I'd be interested in reading about it.

I've read that, too. (Just google it and you will find lots of people complaining.) All I've seen are anecdotes, though, no hard evidence.

Audio quality on SBCs like RPi

Reply #6 –
Quote from: yourlord on
Quote from: saratoga on
The Pi is supposed to be terrible.  No idea about other devices, but I wouldn't be surprised if some of the newer device have more acceptable (if not great) output.


Any links to back up this claim? I'd be interested in reading about it.


I've seen them posted on various forums.  Off hand, I don't recall where.  Try Google?

Audio quality on SBCs like RPi

Reply #7 –
I've seen lots of people disrespect on-board audio chipsets, too. I refuse to believe them unless I see evidence like, say, RMAA tests, etc. I've not seen objective evidence condemning the RPi, but nor have I seen the same exhonorating it of such malign claims.

Audio quality on SBCs like RPi

Reply #8 –
I only use the HDMI audio output of the thing. It wouldn't surprise me if the analog out sucked, but I was looking for some definitive proof. When I first got my Pi I did briefly hook up the analog out to a home audio receiver to test it and as I recall it sounded fine to me but I wasn't really listening that intently for problems. I was really just making sure it worked at all.

Audio quality on SBCs like RPi

Reply #9 –
The term that keeps getting bandied about is 11-bit... but most of the people talking about that 11-bit-ness ignore the fact that it's 11-bit at nearly the Nyquist frequency, which sounds about right for CD-quality audio with proper noise-shaping.

100MHz PWM, apparently? IDK. Can't find proper specifications anywhere. Had to even add a {{citation needed}} to Wikipedia.

Audio quality on SBCs like RPi

Reply #10 –
They just released revision B+ of the Raspberry Pi.

The announcement states that the analog audio out has been improved:
"Better audio. The audio circuit incorporates a dedicated low-noise power supply."

Audio quality on SBCs like RPi

Reply #11 –
Measurements of the analog outs of RPi models B and B+. Even more interesting to me are the comments on the blog entry (which confirm that the analog out is indeed 11 bit).

EDIT - @moderation: I hope it's okay to "link-tard" in this case.

Audio quality on SBCs like RPi

Reply #12 –
What DAC does the Pi actually use?  I didn't see a part listed on the website or mentioned in the bcm2835 manual.

Audio quality on SBCs like RPi

Reply #13 –
I was looking at turning a Pi into a Squeezbox the other day and came across this DAC for it....seems cheap and compact?

http://www.hifiberry.com/

Audio quality on SBCs like RPi

Reply #15 –
Note that neither the Wolfson card, nor the IQaudIO Pi DAC, nor the HiFiBerry work with the new B+ revision. But it's desirable to go for the new revision (better PSU, lower power consumption, USB ports can provide more power).

Audio quality on SBCs like RPi

Reply #16 –
I wouldn't advise the Wolfson DAC. When I read about it to improve my Pi's sound quality, I came across several posts where users complained about how painful the drivers were to compile. It may be a deal-breaker for some people.

One SBC I would recommand for audio is the Odroid. The boards comes with a max98090 from Maxim Integrated (reference can e found here : http://www.maximintegrated.com/en/products.../MAX98090.html). I had the pleasure to work with it on a mobile platform (smartphone) during an internship : the goal was to evaluate the IC and get reference values to compare our implementation with the demonstration board. All our measurements were made with an Audio Analyser from AP (not sure if it was the APx525 or APx585). Globally the results were very satisfying : on the demonstration board, we always measured a SNR > 100dB. Sadly the full measurements were destroyed when the company closed (Renesas Mobile, for those who know) and I didn't get to keep them due to a NDA. Remember though that the Odroid is a different board, and that the performance could be deteriorated. I didn't do any measurement on this particular board, as I only recently left the audiophile community and don't have any tools (yet) to do it.
I'm not sure about the quality of drivers under other OS than Android, as this chip was primarily designed for smartphone. Also, the Odroid processing power might be overkill for your application, too.

Though this isn't as documented as I'd like it to be (and as the rules would, as I understand), I can assure you that the MAX98090 is a quite good chip that does the job correctly.

Edit : I forgot to add : on my Pi, some codecs (namely Opus) were a kinda heavy load on the CPU. I still have to test with native 48kHz files to check if the resampling isn't the cause. also, I don't know if the codec is optimized for armv11 or only later architectures.

Audio quality on SBCs like RPi

Reply #17 –
Quote from: saratoga on
What DAC does the Pi actually use?  I didn't see a part listed on the website or mentioned in the bcm2835 manual.

As stated in the comments sections of the measurement article, it's a software-controlled PWM output (essentially the modern-day version of your trusty PC speaker) run into a digital buffer followed by an R/RC network. Very... basic. Makes most any of these old '90s sound chips look really high-tech, CMI8338 (!) included.

Dang, Arny Krueger's old website appears to be gone from the Internet Archive, and I don't think I ever bothered to save a local copy.  Bummer.  That would've been handy now.

Audio quality on SBCs like RPi

Reply #18 –
How about an Intel NUC?  The 2820 has HDMI and analog out.

Audio quality on SBCs like RPi

Reply #19 –
Quote from: PDG on
Edit : I forgot to add : on my Pi, some codecs (namely Opus) were a kinda heavy load on the CPU. I still have to test with native 48kHz files to check if the resampling isn't the cause. also, I don't know if the codec is optimized for armv11 or only later architectures.


You're probably using the floating point decoder, which won't work well since the Pi doesn't have much of an FPU. 

FWIW, I put some time into optimizing opus for rockbox using a raspberry pi.  Provided you configure the decoder correctly, its quite fast, as opus complexity is not much worse than MP3, and the Pi is many times faster than the average mp3 player.

Audio quality on SBCs like RPi

Reply #20 –
Quote from: stephan_g on
Quote from: saratoga on
What DAC does the Pi actually use?  I didn't see a part listed on the website or mentioned in the bcm2835 manual.

As stated in the comments sections of the measurement article, it's a software-controlled PWM output (essentially the modern-day version of your trusty PC speaker) run into a digital buffer followed by an R/RC network. Very... basic. Makes most any of these old '90s sound chips look really high-tech, CMI8338 (!) included.


I saw that comment, but the output is surprisingly good for something so poor, so I wasn't sure if it was correct.

Audio quality on SBCs like RPi

Reply #21 –
Quote from: audiophool on
I am looking to expand my setup of playback devices for mpd and Logitech Media Server. (That's not the only intended use, I might want to have these devices interact with additional standards and protocols like Miracast or DLNA.)

I already have two Raspberry Pis (RPis). I use them in conjunction with external USB audio interfaces. It works fine, but those external DACs add to the cost as well as to the size of the device. I'm also aware that for some devices, internal add-on DACs exist, but you need to be able to solder for that.

To get to the point: there are now a gazillion of single-board computers (SBCs) which are potential candidate devices for my intended use. Raspberry Pi, ODroid, and Wandboard, just to name a few. Has anyone any experience with the analog outputs (mini-jack or RCA) on any of those? Or maybe even ran RMAA tests?

The sheer number of available SBC options confuses me. I hope information about the sound quality of various SBCs would help me narrow things down. I also think this information may be useful to other readers of this forum.


I went looking for this too, and I can confirm that this is an unfilled niche. There is NO audiophile SBC. The solution is either SBC + USB DAC, or SBC + audio board like HiFiBerry. The former has a lower cost floor (more competition in this market drives prices down), and a higher quality ceiling (ubiquitous interface means more demand and more niches reaching the high end). The latter addon boards are more physically elegant, but that's about it.

The day there is an audiophile SBC, I'm certain the guy at http://volumio.org/devices/ will mention it! For now I ordered a HiFimeDIY USB DAC. I like the mid-range stuff that uses high-end chips. The Volumio guy recommended more DAC hardware here: http://www.raspyfi.com/the-right-usb-dac-f...r-raspberry-pi/

Audio quality on SBCs like RPi

Reply #22 –
Quote from: Canar on
I've seen lots of people disrespect on-board audio chipsets, too. I refuse to believe them unless I see evidence like, say, RMAA tests, etc. I've not seen objective evidence condemning the RPi, but nor have I seen the same exhonorating it of such malign claims.


Dear Canar,

recently I read an interesting article on Tom's hardware titled "What Does It Take To Turn The PC Into A Hi-Fi Audio Platform?" (subtitle "Anything Above $2 Buys More Features, Not Better Quality"). As far as I remember, no RMAA tests were presented, but at least a blind listening test was performed.

Audio quality on SBCs like RPi

Reply #23 –
Quote from: audiophool on
Note that neither the Wolfson card, nor the IQaudIO Pi DAC, nor the HiFiBerry work with the new B+ revision. But it's desirable to go for the new revision (better PSU, lower power consumption, USB ports can provide more power).


But if you read the news/blog, the guy who does the HiFiBerry is working on it for the B+.

All this talk of Model A, B, B+ reminds me of my dad's BBC Model A

Audio quality on SBCs like RPi

Reply #24 –
Quote from: probedb on
But if you read the news/blog, the guy who does the HiFiBerry is working on it for the B+.

Sure, and I appreciate the suggestion. Also, as the so-called P5 header on the Pi will move to the GPIO, one can conveniently plug in the new models of the HifiBerry and the IQaudIO Pi DAC in the B+ without soldering. If the price is right, I'll certainly get one of those (or a revised Wolfson card, if there will be one).

I still think it's wise to purchase B+ revision boards going forward. Once again, they really improved the power supply with it. The USB ports on earlier revisions were severely power-limited (140 mA per port if I recall correctly). Even though that wasn't an issue with my existing external USB DACs, it can be an issue with other peripherals such as USB keyboards.