Tag Archives: hifi

Raspberry Pi does Audio at the Wigwam HiFi Show 2016

The Wigwam Hifi Show is an unusual event, in that most of the exhibitors are not vendors with their latest and shiniest, but enthusiasts showing off their own systems. It is a lot of fun, with plenty of exotic and/or old equipment that you will not see or hear elsewhere.

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I have exhibited at the show in the past, and try to do something a little different each time. This year I thought it would be interesting to contrast the many multi-box and expensive systems with something at the other end of the scale. I was impressed when I reviewed the IQAudio Pi-DigiAMP+ for issue 36 of the MagPi magazine, so I took it along.

This unit is a board that plugs in on top of the main Raspberry Pi board.

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It is very simple, the only external connectors being power in, and left and right speaker terminals. It includes a DAC and a class D amplifier, based on the Texas Instruments (TI) TAS5756m chipset. The DAC is based on a Burr-Brown design.

I assembled my unit using a Raspberry Pi 2, the above board, and the matching case and power supply from IQ Audio. The power supply is the XP Power VEF50US15 which means I get up to 2x20w; if you use a VEF65US19 you can get 2x35w (both available from the IQAudio site).

Here it is in the room at Scalford Hall, home of the Wigwam event.

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The speakers shown are the Cambridge Audio Aero 6, though we also had a pair of Quad 11L and tried them both.

The way things work at this event is that you sleep in your room the night before, and the next morning the bed is removed and it becomes your exhibition room. Having tried the system with the bed in place, I was distressed to find it sounding markedly worse (bloated bass) once the bed was removed. With no time for proper experimentation we dragged the mattress back out of the cupboard and leant it against the wall, which improved matters; we also used foam bungs in the speaker ports to tame the bass. Not ideal, but shows the difficulty of getting good sound at short notice in small hotel rooms.

The Cambridge Audio Aero 6 speakers I would describe as a good budget choice; they sell for around £350. Philosophically (as with the Quads) they are designed to be clean, detailed and uncoloured. The choice of floorstanders rather than small standmounts was deliberate, as I wanted to demonstrate that using a tiny amplifier does not necessarily mean a small sound.

Having said that, we also put the Quads on from time to time, which are small standmounts. The sound was not radically different, though bass extension is less and to my ears the 11Ls are a little less precise than the Aeros, with a warmer sound. I preferred the Aeros but as ever with loudspeakers, tastes vary.

The complete parts list as shown:

  • Raspberry Pi 2 £26.00
  • IQAudio Pi-DigiAMP+ £57.99
  • IQAudio Pi-CASE+ £15.60
  • 15v Power Brick XP Power VEF50US15 £25.50

If I were buying today, I would recommend the new Raspberry Pi 3 and the more powerful 19v power supply which increases the cost by about £10.00.

So that is between £125 and £135 for the complete device, and then whatever you choose for the speakers.

For the demonstration I brought along a router with wi-fi, to which I attached a hard drive with lots of FLAC files ripped from CD, along with a few high-res files. The router lets you attach a USB drive and share it over the network, so I configured Volumio on the Pi to use that as its source. In a typical home setup, you would probably store your music on a NAS device and use your existing home network.

Where’s the amplifier?

There was a steady stream of visitors from around 10.00am to the close of the show at around 17.00. The goal was not to be the best sound at the show, but rather to be the smallest and still deliver decent sound quality, and for many visitors I think we succeeded. We stuck the equipment list on the wall and lots of people photographed it with the intention of looking into it further.

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A demo under way: spot the mattress leaning against the wall and the smaller Quad speakers alongside the Cambridge Audios.

A number of visitors knew of, or were even using, a Pi for streaming, but the idea of having the amplifier included on a small board was less familiar; it was fun when people asked where the amplifier was, or whether the speakers were active (they are not). Some were really astonished that you can get respectable sound quality from such a small box.

Volume was more than sufficient for a room this size and frankly plenty for most home situations though of course not for huge rooms or loud parties.

Note that despite playing loud throughout the day the amp board did not get warm at all; this is because a Class D design delivers almost all the power supplied as output to the loudspeakers.

A few early comments from the forums:

“The super small Raspberry Pi based system by onlyconnect was a brilliant demo of what can be achieved by something tiny and low cost.”

“I wouldn’t have thought it possible if I hadn’t have heard it… To boot, completely taking price out of the equation, it was one of the better sounding systems at the show to my ears, I enjoyed that more than some far, far more expensive rigs.”

“Highlights. Onlyconnect’s raspi based system, honestly why pay more for music around the house?”

“Onlyconnect’s Raspberry system was impressive and wins the GVFM award.”

“Onlyconnect’s mini/budget system – just amazing how good a £125 raspberry pi setup containing streamer, dac, preamp and 35w per channel amp could sound. I can’t forget how flabbergasted another listener was to discover the total system cost  -” I’ve obviously doing it all wrong all these years”

“I spent a while looking for the amplifier, following the cables etc like everybody else. I was impressed by the sound coming out of the Cambridge Audio speakers, I would certainly put this in the top 40% of rooms based on the sound quality, maybe higher.”

High end home entertainment with a Cornflake flavour

Tucked away on a side street off London’s Tottenham Court Road is The Cornflake Shop, which appeared back in the Eighties to sell high-end audio equipment with a more considered service than was available from the multitude of hi-fi shops which, at the time, thronged the main road.

Since that time the audio industry has changed and many dealers have struggled or closed. Hi-fi today, for most people, means an iPhone dock or a set of powered speakers. Despite those challenges, on a recent visit to London I was interested to see that the Cornflake Shop lives on; in fact, they have just opened a new showroom called the Art of Technology, Realised and whose window declares “The Smart App-artment”.

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I could not resist a visit. Inside it has a striking animated graphic projected on the wall and framed artefacts – a typewriter, an old tape recorder.

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I chatted with them about the state of the audio industry and was told that the their business had transitioned to something more like automating the home, but still with a strong element of home entertainment; they aim to have every installation include a fine music system. However they will still sell you just a CD player or a pair of loudspeakers if you ask, and now intend to renew their focus on high-end audio alongside the other things they do.

Go downstairs and a series of subterranean showrooms demonstrate various home environments.

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The back room, if that is the right word, is amazing; racks of networking gear, home entertainment controllers, music and video servers. They use Sonos for multi-room audio and Kaleidoscope, which lets you legally rip Blu-Ray to a server, for video.

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Would someone really have something like this in their home, I asked? Oh yes was the answer.

Then it was time to listen to some music. These striking Martin Logan loudspeakers from the Reserve ESL series combine electrostatic drivers for the mid-range and treble with a conventional sub-woofer.

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Spot the valve amplifier. What on earth are valves doing in an ultra-modern home entertainment setup? The answer is simply that they like the sound. There is an element of retro here.

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We played a couple of tracks, selected from an iPad app, and a music video, for which a large screen slid elegantly into view. It sounded good but I did not stay long enough to be able to comment in detail.

The Cornflake Shop always had its own individualistic and slightly quirky approach and it is great to see that this continues. You will get something stylish for your money that will deliver high quality home entertainment. But how much back-end kit do you need in the modern home? If you are looking for the minimum amount of wires and the smallest amount of equipment, this might not be the place for you.

Dear audio industry, fix mastering before bothering with high resolution

The audiophile world (small niche though it is) is buzzing with a renewed interest in high resolution audio, now to be known as HRA.

See, for example, Why the Time is Right for High-Res Audio, or Sony’s new Hi-Res USB DAC System for PC Audio, or Gramophone on At last high-resolution audio is about to go mainstream, or Mark Fleischmann on CD Quality Is Not High-Res Audio:

True HRA is not a subtle improvement. With the best software and hardware, a good recording, and good listening conditions, it is about as subtle as being whacked with a mallet, and I mean that in a good way. It is an eye opener. In lieu of “is that all there is?” you think “wow, listen to what I’ve been missing!” … The Compact Disc format is many good things but high-res it is not. It has a bit depth of 16 and a sampling rate of 44.1 kHz. In other words, it processes a string of 16 zeroes and ones 44,100 times per second. Digitally speaking, this is a case of arrested development dating back to the early 1980s. We can do better now.

As an audio enthusiast, I would love this to be true. But it is not. Fleischmann appears to be ignorant of the Nyquist-Shannon sampling theorem, which suggests that the 16-bit/44.1 kHz CD format can exactly reproduce an analogue sound wave from 20–22,050 Hz and with a dynamic range (difference between quietest and loudest signal) of better than 90Db.

Yes there are some ifs and buts, and if CD had been invented today it would probably have used a higher resolution of say 24-bit/96 Khz which gives more headroom and opportunity for processing the sound without degradation; but nevertheless, CD is more than good enough for human hearing. Anyone who draws graphs of stair steps, or compares CD audio vs HRA to VHS or DVD vs Blu-Ray, is being seriously misleading.

Yes, Sony, you are a disgrace. What is this chart meant to show?

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If shows that DACs output a bumpy signal it is simply false. If it purports to show that high-res reproduces an analogue original more accurately within the normal audible range of 20-20,000 Hz it is false too.

As an aside, what non-technical reader would guess that those huge stair steps for “CD” are 1/44,100th of a second apart?

The Meyer-Moran test, in which a high-res original was converted to CD quality and then compared with the original under blind conditions (nobody could reliably tell the difference), has never been debunked, nor has anyone conducted a similar experiment with different results as far as I am aware.

You can also conduct your own experiments, as I have. Download some samples from SoundKeeper Recordings or Linn. Take the highest resolution version, and convert it to CD format. Then upsample the CD quality version back to the high-resolution format. You now have two high-res files, but one is no better than CD quality. Can you hear the difference? I’ve yet to find someone who can.

Read this article on 24/192 Music Downloads … and why they make no sense and watch the referenced video for more on this subject.

Still, audio is a mysterious thing, and maybe in the right conditions, with the right equipment, there is some slight difference or improvement.

What I am sure of, is that it will be nowhere near as great as the improvement we could get if CDs were sensibly mastered. Thanks to the loudness wars, few CDs come close to the audio quality of which they are capable. Here is a track for a CD from the 80s which sounds wonderful, Tracy Chapman’s debut, viewed as a waveform in Adobe Audition:

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And here is a track from Elton John’s latest, The Diving Board:

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This everything louder than everything else effect means that the sound is more fatiguing and yes, lower fidelity, than it should be; and The Diving Board is far from the worst example (in fact, it is fairly good by today’s standards).

It is not really the fault of recording engineers. In many cases they hate it too. Rather, it is the dread of artists and labels that their sales may suffer if a recording is quieter (when the volume control is at the same level) than someone else’s.

Credit to Apple which is addressing this to some extent with its Mastered for iTunes initiative:

Many artists and producers feel that louder is better. The trend for louder music has resulted in both ardent fans of high volumes and backlash from audiophiles, a
controversy known as “the loudness wars.” This is solely an issue with music. Movies, for example, have very detailed standards for the final mastering volume of a film’s
soundtrack. The music world doesn’t have any such standard, and in recent years the de facto process has been to make masters as loud as possible. While some feel that overly
loud mastering ruins music by not giving it room to breathe, others feel that the aesthetic of loudness can be an appropriate artistic choice for particular songs or
albums.

Analog masters traditionally have volume levels set as high as possible, just shy of oversaturation, to improve the signal-to-noise ratio (SNR). With digital masters, the goal
is to achieve the highest gain possible without losing information about the original file due to clipping.

With digital files, there’s a limit to how loud you can make a track: 0dBFS. Trying to increase a track’s overall loudness beyond this point results in distortion caused by
clipping and a loss in dynamic range. The quietest parts of a song increase in volume, yet the louder parts don’t gain loudness due to the upper limits of the digital format.
Although iTunes doesn’t reject files for a specific number of clips, tracks which have audible clipping will not be badged or marketed as Mastered for iTunes.

Back to my original point: what is the point of messing around with the doubtful benefits of HRA, if the obvious and easily audible problem of excessive dynamic compression is not addressed first?

None at all. The audio industry should stop trying to mislead its customers by appealing to the human instinct that bigger numbers must mean better sound, and instead get behind some standards for digital music that will improve the sound we get from all formats.

Hi-res audio and the hi-fi press: the problem with honesty

I have posted several articles on the subject of high resolution audio – here, for example. It is a subject that fascinates me. I enjoy music more if it is accurately reproduced, and regard sound quality as something worth paying for, but is it worth investing in high resolution formats such as SACD, DVD Audio, 24/96 and higher FLAC or ALAC (Apple’s lossless audio format); or is it better to concentrate on other parts of the audio chain, on the grounds that even lowly CD and 16/44 capture music with an accuracy close to the limits of what human hearing can perceive?

Many audio enthusiasts swear that high-res formats sound much better; but solid evidence for their superiority as a delivery format is hard to come by, and when you perform simple tests like converting a high-res format into one at CD resolution and comparing the two, it is often (perhaps always) hard to hear any difference. 

High resolution formats are of course a necessity in music production, where the sound will be processed, possibly many times over, before the final master is complete.

Alan Sircom is the editor of the UK audio magazine hi-fi plus. In a frank forum discussion concerning the challenges of editing such a magazine today he makes the following remark:

For all the enmity you and yours have toward the magazine, our biggest potential loss of readers right now is coming from my stance on hi-res. I still maintain that you are paying a premium for microphone thermal noise and – at best – a more careful mastering process. I know a lot of manufacturers of DACs who (privately) agree with me… but have to continue to develop their products from 24/96 to 24/192 to 32/384 to DSD-over-USB because the audiophiles (who, let’s face it, buy our stuff) will not accept anything less. This is a sham, especially as there is a better campaign to be had (something like “brick-wall mastering is worse than brick-wall filtering”, but more pithy). However, the upshot of the excellent exposé of the hi-res game by Hi-Fi News did not cause an army of hi-res-loving audiophiles demanding more from their hi-res, it caused some of them to consider Hi-Fi News ‘hostile’ to hi-res.

If true, this is a depressing situation. The goal of home audio is to achieve the best possible sound at home within your budget, which means investing in the technology that makes the most audible difference. It is not easy to discern what that is though, which is where an independent press has a valuable role to play. According Sircom, that is difficult to do in practice, because of the constraints imposed by the economics of advertising at one end, and a readership which does not always want to hear the truth at the other.