Volumio goes to x86…

…and I’m rather excited.

I’ve been a fan of the Volumio Project for rather a while now, since discovering it as a good platform for my Raspberry Pi audio player a year or more ago.  Several self-built MPD-based setups have come and gone since the Raspberry Pi arrived, but Volumio has been the mainstay for reliable playback with control from numerous devices.  The main draw for me has been the combination of its web interface, the fact the hard work has been done for me in terms of getting all the software components working together, and the fact that the whole package does seem to sound good.

On reflection I’m not sure that the various “audio optimizations” at the kernel or any other level really make an audible difference, but I do know that the whole package does seem to work more reliably on the limited resources of Raspberry Pi hardware than anything I’ve been able to cook up myself, at least without significant effort expended.

So why does an x86 port excite me so much?  Two reasons:

  1. More processing power availability opens the platform up to interesting things like DSP and dual-use such as streaming to remote machines and the like without falling over.  Presently I’d have multiple Raspberry Pi’s set up with dedicated tasks.  That’s been educational, but arguably a lot of hassle to set up and maintain. A single machine would make some of this stuff easier.
  2. Opening up the platform to more common (and more powerful) hardware fvastly extends the range of audio and storage hardware that can usefully be used with it, and perhaps extends Volumio’s exposure on the wider marketplace.

The Raspberry Pi is an amazing platform for what it is – and audio systems based upon its limited bus bandwidth are capable of sounding incredible. But not everyone has a NAS to throw their music onto, which makes the Pi’s USB2 storage a pain to deal with when using it for networking, local storage AND the audio device all at the same time.  And even those two do use it with a NAS are hampered by the 100MB Ethernet connection.  Sure, streaming even “HD” audio files  won’t tax it, but storing, backing up and indexing large audio collections will.  And THIS is where even an old Netbook could best it.

At some point where time allows, I’m looking forward to putting my elderly ASUS Netbook through its paces with a 192KHz-capable USB2 audio device and either a USB drive or “Gigabit” Ethernet adaptor (its own onboard Ethernet, like the Pi’s, is limited to 100MB), to see how it stacks up against the Pi running on the same hardware.  I know from running the RC download today that the distro works and plays audio even on the onboard audio, and the default setup to use the onboard display, keyboard and mouse to show the Web interface by default is a lovely touch.

 

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Raspberry Pi HDMI audio vs USB CPU use

Quick note after some experiments last night. Not completely scientific, but enough to show a trend. I set out to compare CPU usage of the Pi running Volumio, upsampling lossless 44.1KHz 16bit stereo with ‘fastest sinc’ to 192KHz 32-bit stereo.

Streaming to the USB uses between 70 and 90% CPU. Streaming to the HDMI output uses 95% and more! Audio gets choppy in the latter case even without other processes getting in the way, whereas the former only gets choppy when the Pi happens to try and update the MPD database at the same time.

Wonder if anyone knows why onboard streaming should use so much extra CPU time to do the same work, and whether I2C suffers the same fate? Not sure I want to spend on a custom DAC if the current EMU 0202USB is more efficient?

Getting an EMU 0202USB working with a Raspberry Pi

In the last couple of weeks, out of curiosity, I’ve bought a Raspberry Pi to play with at home.  It’s really very impressive to see what can be done these days with a $35 computer – an “educational” model at that!

Our Pi is currently in place as our digital audio player, courtesy of the Volumio linux “audiophile” distribution, and an EMU 0202 USB audio interface.

Once the Pi was booting Volumio off the SD card, I found two things that needed doing:

  1. Set up the Pi to pull files off our NAS device.  In theory this can be done from the Volumio web interface, but I had to go hacking around editing config files to make this work seamlessly.
  2. Set up the EMU for optimal digital playback.  I take a somewhat different path on this to most “audiophiles”.  I’m specifically aiming to implement a software volume control, provided I can run the digital audio chain at 88.2KHz/24bit, or higher.  This means CD/MP3 content gets upsampled, while some recordings made natively at 88.2KHz/24bit get to be played that way.

The Volumio forums helped me out with point 1, but I’ve lost a lot of brainpower and free time to getting the EMU to work properly.  I could get it to play out at 44.1KHz/24-bit, but any attempt to play native files at higher rates, or to have MPD upsample, resulted in obviously robotic-sounding distorted playback.  It turns out the key was simple:

It seems the clock rate on the EMU 0202 and 0404 USB devices is assigned to a fader in ALSA, which in this case I accessed using alsamixer.  There were two faders for my 0202:  PCM and Clock rate Selector.

The latter has a range of stepped values, equating to the following sample rates:

  •   0% 44.1KHz
  •  20% 48.0KHz
  •  40% 88.2KHz
  •  60% 96.0KHz
  •  80% 176.4KHz
  • 100% 192.0KHz

What I’ve learned then is that to get the setup working, I needed to not only set Volumio (or the underlying MPD player) to resample to the target output rate of 88.2KHz/24-bit but ALSO to set the Clock rate Selector to 40% in alsamixer.

All works happily and I’m loving the more “analogue” sound of the EMU in that mode!

UPDATE, 23RD FEB 2014:

I’ve managed to get MPD to reliably resample to 176400Hz/24-bit (32-bit internal, 24-bit at the card.) by forcing the Pi’s turbo to “always on” and a slight overclock. It’s not *quite* perfect yet, so i might see if I can push it a little harder before documenting our full setup.

Review: Rega Carbon MM cartridge

Image

(Rega Carbon MM conical cartridge; Image from Rega website)

In recent months I’d found our vinyl playback becoming increasingly distorted, especially on sibilants.  It seemed to me that our beloved Denon DL-160 MC cartridge tip has seen better days, and likely needs repair or replacement.  The problem was, with what should we replace it, even only for a short time while it’s away?

I had already kept a backup in our Ortofon DN165 with an OM-5 “generic” stylus which never really seemed to fully “sing” up against the Denon, but a quick swap showed that it was indeed more able to track inner grooves far better and with far less sibilance than the Denon was showing, especially on the recent Pulp “Different Class” 180G reissue which seems to be very densely packed towards the end of side 1.

But – the Ortofon really is no match in terms of tonality on our Dual 505-II compared with what the Denon could do with a new tip.  So, while we started to work out what do with the Denon, I hit up some online forums to see what people think of the cheapest available cartridges.  This narrowed the choice mostly to Audio-Technicas, either the AT-91 or the AT-95E.  Then I came across the Rega Carbon, which was well regarded in these two reviews:

http://audiofi.net/2013/03/rega-carbon-cheerful-cheapie-cartridge/

http://theartofsound.net/forum/showthread.php?21594-Using-a-Rega-Carbon-cartridge

So – for about £27 including delivery, I ordered on Amazon and was surprised to have one delivered to me by Sevenoaks Audio.  I mounted it within minutes of arrival and spun a few discs before leaving for a holiday.

First impressions…

…surprisingly good.  The overall balance was very similar to how I remembered the Denon DL-160 sounded when it was new to us.  Tracking ability of the deck was much improved – and it cleaned up many of the distorted sibilants in our rather well-loved first-run copies of Michael Jackson’s “Thriller”, and Al Stewart’s “Year of the Cat”.

Since our return, I’ve spun another varied and very enjoyable 10-15 discs with it, and am now sat enjoying a lovely rendition of an 80’s repressing of Pink Floyd’s DSOM.   So now I’m collecting some brief thoughts on how it now sounds after some 15-20 hours of playing time.

Longer term impressions…

It’s settled down – a lot.  The initial slightly brash treble presentation has become much more smooth, and surprisingly detailed considering how I’d have expected a conical stylus to sound, based on my limited understanding of the physics involved.  It rarely sounds as if it’s missing any significant high-frequency detail, though it’s fair to say its useful upper-limit in its frequency response is perhaps 1-2KHz lower than the Denon.

Surface noise is much-reduced compared to the tired Denon or mid-life Ortofon.  I’m therefore feeling much more able to just plunk a clean-looking disc down and get the needle stuck-in without spending significant cleaning time.

The overall sound is now much more balanced across the whole playing surface of any disc.  The balance change from “The Great Gig in the Sky” (end of Side 1 DSOM) to “Money” (beginning of Side 2 DSOM) is much less noticeable.  The latter sounds absolutely stunning in its detail, overall balance and sound-staging.  The tightness of the room reverb in the recording studio is now absolutely evident, with the background sounding “darker” than ever before.  The cymbals are absolutely crisp, as are the vocal sibilants.

Again sticking with DSOM as the example, while the apparent width of the soundstage feels narrower with the Carbon than with the Denon DL-160, the apparent depth of the soundstage feels much more accurate. Centre-panned voices seem to stand forward of the rest of the band. Individual instruments take on a definite space and are much more able to be followed than with the Ortofon.  Arguably in this more subjective respect, the cartridge does as good a job as the Denon ever did in our rig.  In some ways, it’s better – fine details seem much more apparent, and solid, than I’ve ever heard on this rig before.

“Us and Them” – the Rega pulls sparkle and space out of a dense mix in an increasingly tricky part of the disc.  It actually makes our rather tired copy sound brand-new. The huge chorus section has always sounded screechy with either of our previous cartridges – but with the Rega it just sounds big, and heavy and much cleaner.  Fine details of Sax placement, piano, organ and guitar riffs, complete with their acoustic space, are still audible even in the really heavy sections.  The synths, guitars and organ in the closing section perhaps have less sparkle than I remember, but their placement in the soundfield is much more assured, and much less distorted.

The overall impression is that this cartridge is a stunner – and it simply delivers *music* at whatever pace was intended. It delivers space and detail enough to communicate the message, if not always to convince you that the band is playing live right in front of you. And it does all of this without any apparent resonant tradeoff, nor any significant omission in any other area.

So – maybe I had a duff DL-160, and maybe our Ortofon had seen better days.  Maybe the DL-160 was perhaps a less-than-ideal match for our deck. But whatever the reasons for the differences I’m hearing, this cartridge absolutely *sings*, and it does so with a poise and fun-factor that I’d always heard vinyl was supposed to offer.   The Denon got us there for a good year or more, and I when I add up its total known playing-time in our care it’s really about time it was repaired or replaced.

Then I consider the price-tag, and I can only conclude that regardless of its peers, the Rega Carbon is an absolute gem and works incredibly well with our Dual 505-II, with its ultra-light original tonearm and (admittedly) customised heavy non-suspension base.

I’d tell any vinyl lover to just buy one to try for novelty-value, regardless of whatever other “prestige” cartridges you might also have. You might be surprised at how well it actually compares.  It’s always good to have a more-than-passable backup to a much better cartridge – but in our case, I’m suddenly in much less of a hurry to re-tip or replace our beloved Denon. I now have the time to get it right.

Oh, and if you need more evidence to commend this little gem – I can tell you one more thing:

Any good hifi component, or system, should make you want to listen to your music more.  Judging by the pile of played discs building up on my desk that need putting back onto the shelves, I can tell you that this has certainly got us listening to a *lot* more music, in a phase of live when I can tell you we’ve had the least actual *time* to listen to it.

Online music streaming – missing a note or two?

Google Play logo, courtesy Wikipedia
Google Play logo, courtesy Wikipedia

Quick thought, while I’m procrastinating…

While I’m not planning to let go of physical media anytime soon – not least the vinyl collection, I’m becoming a huge fan of Google Play, and its ability to play music “uploaded and matched” from my own collection.  Real bonuses for me are that this happens for no extra cost to my Google Apps domain, and  it seems to work well wherever I have a reliable ‘net connection.  The quality when listening via headphones and Google Chrome on a laptop is surprisingly good considering they’re MP3’s – possibly transparent enough to pass a proper ABX test between them and the original uncompressed digital stream on CD.

But something is different, and something is missing… quite a lot of things are missing actually.

Where’s the song information?

Geeks might call this “metadata”. The information about the making and content of the recording is as useful to me as the actual content itself.  I like knowing things like, who wrote the song I’m listening to. I might want to check the lyrics. I might also want to know whether I’m listening to a particular remaster or reissue.  While the content and artwork are there on Google Play, I’ve got absolutely no idea at first glance which exact version or release of a song I’m listening to.

At present, I know who the release artist is for a song as it plays, and from which album. I can even see the album artwork for the majority of my collection, as well as a release year.  What I don’t know without doing a *lot* more digging is whether the particular copy of “Bohemian Rhapsody” I’m listening to is from a 1990’s remaster, or the more recent (2011?) remasters? I’m not ordinarily such a geek – a great song is a great song whatever the media it’s carried on.  But it’s good to know nonetheless.  Especially if I happen to like the work of a particular mix/master engineer, or if I purchased a particular CD release of an album due to a known heritage, which has been matched to another version which sounds particularly different.

I think it would be really nice if digital streaming/shop purveyors could actually provide the full information of the songs they’re sending us.  There are more involved in most major releases than just the artists, and it’s only right that they get the credit, even if the information shows no significant other commercial purpose.

What even made me think of this?

Listening to the current version of Queen’s “A Kind of Magic” up on Google Play, I’m noticing a lot more musical and tonal detail in the recordings than I remember from my own CD copies.  This is an album I’ve known for the whole of my musical life, and I therefore have some very strong memories of it, and can recall absurd amounts of detail regarding both musical arrangements and sonic character and how they were reproduced differently in each of the releases I’ve owned copies of.  Since I’m hearing so many new things despite listening on familiar equipment, I’d like to understand where they come from.  Since I like the differences, I’d like to know if they are due to a particular engineer’s approach to remastering, and whether I can find more by the same engineer.  Or whether I can learn something about the engineering approach that led to the result I liked so much.

On the one hand the freedom offered by always-on streaming access like this is wonderful – but on the other it comes with a lot of compromises, and with a lot of things “hidden” from view that I feel really should be open to us all…

Tempted to bang on the walls to alert your noisy neighbour to your plight?

Don’t.

Firstly and as many Londoners might naturally feel, there is of course the very practical consideration that fighting back in this way tends only to inflame an already delicate situation. Secondly, here in the UK at least, in your malice you might be creating an actionable private nuisance yourself!

Sound strange? Maybe, but look what happened when this kind of case was brought to court, many moons ago…

The case of Christie v Davey, 1893, 1 Ch 316

Seems that Christie here was a music teacher, who gave lessons in her house. Mr Davey, living in the semi-attached property next door, didn’t much like the noise. It seems he complained directly to Mrs Christie more than once. I’ve just found online a letter purporting to be penned from Mr Davey to Mrs Christie:

“During this week we have been much disturbed by what I at first thought were the howlings of your dog, and, knowing from experience that this sort of thing could not be helped, I put up with the annoyance. But, the noise recurring at a comparatively early hour this morning, I find I have been quite mistaken, and that it is the frantic effort of someone trying to sing with piano accompaniment, and during the day we are treated by way of variety of dreadful scrapings on the violin, with accompaniments. If the accompaniments are intended to drown the vocal shrieks or teased catgut vibrations, I can assure you it is a failure, for they do not. I am at last compelled to complain, for I cannot carry on my profession (the defendant was an engraver) with this constant thump, thump, scrap, scrap, and shriek, shriek, constantly in my ears. It may be a pleasure or source of profit to you, but to me and mine it is a confounded nuisance and pecuniary loss, and, if allowed to continue, it must most seriously affect our health and comfort. We cannot use the back part of our house without feeling great inconvenience through this constant playing, sometimes up to midnight and even beyond. Allow me to remind you of one fact, which must most surely have escaped you–that these houses are semi-detached, so that you yourself may see how annoying it must be to your unfortunate next door neighbour. If it is not discontinued, I shall be compelled to take very serious notice of it. It may be fine sport to you, but it is almost death to yours truly.”

Evidently the letter (which is also referenced and indeed quoted here) didn’t have much effect, and so it seems that Mr Davey took to making noise in retaliation whenever he heard anything from Mrs Christie.  Mr Davey’s noise in turn distracted Mrs Christie’s music lessons, and so Mrs Christie took Mr Davey to court to get him to stop.  According to records I’ve found cited many times online, it would seem that the court ruled in favour of Mrs Christie and granted an injunction against Mr Davey.

Surprised?

When I first heard this story, it was told as Mr Davey having brought the case to court, to get Mrs Christie to stop her teaching activities, and that the court turned the tables on him.  This would have been a much bigger surprise than what I’ve found to have been documented.

Given the presented evidence of his ongoing sufferings, if this case came to court now I might still ordinarily hope for a ruling in favour of Mr Davey. But on reflection, I think there’s an principle at work here:  one cannot justify the creation of a new nuisance, especially out of malice, in order to fix or protest against another.

A lot of water has passed under a lot of bridges since this case originally came to court in 1893.  I’m intrigued to see what others might think of this case in light of our present-day exposure to noise, and whether attitudes have changed about such confrontation.  I wonder if there are any more recent rulings that might counter this one?