Category Archives: hifi

audio, hifi

More on MQA and Tidal: a few observations

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I have signed up for a trial of the Tidal subscription service and have been listening to a few of the MQA-encoded albums that are available. You can find a list here. Most of the albums are from Warner, which is in the process of MQA-encoding all of its catalogue.

From my point of view, having familiar material available to test is a huge advantage. Previous MQA samples have all sounded good, but with no point of reference it is hard to draw conclusions about the value of the technology.

I have used both the software decoding available in the Tidal desktop app (running on Windows), and the external Meridian Explorer 2 DAC which is an affordable solution if you want something approaching the full MQA experience.

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Note that on Windows you have to set Exclusive mode for MQA to work correctly. When using an MQA-capable DAC, you should also set Passthrough MQA. The Explorer 2 has a blue light which shows when MQA is on and working.

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For these tests, I used the Talking Heads album Remain in Light, which I know well.

The Tidal master is different from any of my CDs. Here is the song Born under Punches in Adobe Audition (after analogue capture):

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Here is my remastered CD:

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This is pretty ugly; it’s compressed for extra loudness at the expense of dynamic range.

Here is my older CD:

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This is nicely done in terms of dynamic range, which is why some seek out older masterings, despite perhaps using inferior source tapes or ADC.

This image shows three variants of the track streamed by Tidal and captured via ADC into a digital recorder at 24-bit/96 kHz.

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The first is the track with full MQA enabled and decoded by the Explorer 2. The second is the “Hi-Fi” version as delivered by Tidal, essentially CD quality. The third is the “Master” version, in other words the same source as the first, but with Exclusive mode turned off in Tidal, which prevents MQA from working.

You can see at a glance that MQA is doing what it says it does and extending the frequency response. The CD quality output has a maximum frequency response of 22 kHz whereas the MQA output extends this to 48 kHz at least as captured by my 24-bit / 96 kHz (the theoretical maximum frequency response is half the sampling rate).

Do they sound different though, bearing in mind that we cannot hear much above 20 kHz at best, and less than that as we age? I have been round this hi-res loop many times and concluded that for most of us there is not much benefit to hi-res as a delivery format. See here for some tests, for example.

MQA is not just extended frequency response though; it also claims to fix timing issues. However my captured samples are not really MQA; they are the output from MQA after a further ADC step. Of course this is not optimal but the alternative is to capture the digital output, which I am not set up to do.

An interesting question is whether the captured MQA output, after a second ADC/DAC conversion, can easily be distinguished from the direct MQA output. My subjective impression is, maybe. The first 30 seconds of Born Under Punches is a sort of collage of sounds including some vocal whoops, before David Byrne starts singing. What I notice listening to the Tidal stream with MQA enabled is that the different instruments sound more distinct from each other making the music more three-dimensional and dramatic. The vocals sound more natural. It is the best I have heard this track.

That said, I have not yet been able to set up any sort of blind test between the true MQA stream and my copy, which would be interesting, since what I have captured is plain old PCM.

There is a key point to note though, which is that mastering offered by Tidal is better than any of the CD versions I have heard; the old Eighties mastering is more dynamic but sounds harsher to my ears.

With or without MQA; you might want to subscribe to Tidal just to get these superior digital transfers.

Update: it seems that the Tidal stream for Remain in Light (both MQA and Hi-Fi) is a different mix, possibly a fold-down from the 5.1 release. So it is not surprising that it sounds different from the CD. The question of whether the MQA decoded version sounds different still applies though.

audio, hifi, music industry

The MQA enigma: audio breakthrough or another false dawn?

The big news in the audio world currently, announced at CES in Las Vegas, is that music streaming service Tidal has signed up to use MQA (Master Quality Authenticated), under the brand name Tidal Masters. MQA is a technology developed by Bob Stuart of Meridian Audio, based in Cambridge in the UK, though MQA seems to have its own identity despite sharing the same address as Meridian.

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What is MQA? The question is easy but the answer is not. Here is the official short description:

Conventional audio formats discard parts of the sound to keep file size down, but part of this lost detail is the subtle timing information that allows us to build a realistic 3D soundscape in our minds. … With MQA, we go all the way back to the original master recording and capture the missing timing detail. We then use advanced digital processing to deliver it in a form that’s small enough to download or stream.

At first sight it looks like another format for lossless audio, and the description on MQA’s site confuses matters by making a comparison with MP3:

MP3 brings you just 10% of what was recorded in the studio. Everything else is lost to fit the music into a conveniently small file. MQA brings you the missing 90%.

There are two problems with this statement. One is that MP3 (or its successor AAC) actually sounds very close to the original, such that in tests most cannot tell the difference; and the other is that audiophiles tend not to use MP3 anyway, preferring formats like FLAC or ALAC (Apple’s version) which are lossless.

There is more to it than that though. There are three core aspects to MQA:

1. “Audio origami”: MQA achieves higher resolution than CD (16-bit/44.1MHz) by storing extra information in audio files that is otherwise wasted, as it stores audio that is below the noise floor (ie normally inaudible). There is a bit of double-think here as removing unnecessary parts of audio files is the sort of thing that MP3 and AAC do, which the MQA folk have told us is bad because we are not getting 100%.

This is also similar in concept to HDCD (High Definition Compatible Digital), a technology developed by Pacific Microsonics in the Eighties and acquired by Microsoft. Of course MQA says its technology is quite different!

Note that you need an MQA decoder to benefit from this extra resolution, and there is a nagging worry that without it the music will actually sound worse (HDCD has the same issue).

2. Authentication. MQA verifies that the digital stream is not tampered with, for example by audio features that convert or enhance the sound with digital processing. This can be an issue particularly with PCs or Macs where the built-in audio processing will do this by default, unless configured otherwise.

3. Audio “de-blurring”. According to MQA’s team:

There’s a problem with digital – it’s called blurring. Unlike analogue transmission, digital is non-degrading. So we don’t have pops and crackles, but we do have another problem – pre- and post-ringing. When a sound is processed back and forth through a digital converter the time resolution is impaired – causing ‘ringing’ before and after the event. This blurs the sound so we can’t tell exactly where it is in 3D space. MQA reduces this ringing by over 10 times compared to a 24/192 recording.

If this is an issue, it is not a well-known one, at least, not outside the niche of audiophiles and hi-fi vendors who historically have come up with all sorts of theories about improving audio which do not always stand up to scientific scrutiny.

So is MQA solving a non-problem? That’s certainly possible; but I do find it interesting that MQA has received a generally warm reception from listeners.

Here’s one audiophile’s reaction:

Have never really “done” digital before. 16/44 has always sounded ghastly to my ears right from the start and still now. MQA did indeed “fix” the various forms of distortion that I could hear present in everything where the sampling rate was taken down to just 44. … My findings – those of an improved sense of solidity in the stereo image and the lack of that horrendous crystalline glassy edge to things, especially on the fade, seem to be being mirrored in what people are hearing. It doesn’t have that thing I describe as a “choppy sense of truncation” which I suspect others mean by “transients”.
Basically, per the post above, it’s a bit like “good analogue”. Digital can finally hold its head up high against an analog from master-to vinyl performance. And not only that, hopefully, walk all over it and give us something genuinely new.

If this history of audio has shown us anything, it is that subjective judgements about what makes something sound better (and whether it is better) are desperately unreliable. Further, it is often hard to make true comparisons because to do requires so much careful preparation: identical source material, exactly matched volume, and the ability to switch between sources without knowing which is which, to avoid our clever brains from intervening and telling us we are hearing differences which our ears alone cannot detect.

We should be sceptical then; and even possibly depressed at the prospect of a proprietary format spoiling the freedom we have enjoyed since the removal of DRM from most downloadable audio files.

Still … is it possible that MQA has come up with a technology that really does make digital audio better? Of course we should allow for that possibility too.

I have signed up for Tidal’s trial and will report back shortly.

audio, hifi, retro

Ripping vinyl with the Plato home entertainment system

I am a tad conflicted when it comes to vinyl records. On the one hand, I have not seen convincing scientific evidence, or a properly conducted blind test, that demonstrates any reason why record replay is superior to digital, while there is plenty of evidence for the reverse. On the other hand, I put on a well-mastered record, and it is like magic, I am transported into the music in a way that my digital sources rarely achieve. Plus the sleeves are beautiful, and in the case of older recordings, a sense that this is the real thing and subsequent formats mere copies (even if they do sound better). Finally, sometimes missing or damaged master tapes, or the bad habits of the recording industry in compressing CD audio so that it is uniformly LOUD, mean that records sometimes really do sound better, despite the limitations of the format.

If you like the sound of records but the convenience and security against damage that digital offers, you might want to rip them. I have done this but would not describe it as easy. You have to play the record in the closest to ideal conditions you can manage – clean record, no dust accumulated on the stylus, high quality turntable and phono stage – while also recording the output through an analogue to digital converter (ADC). Then when done, you have to break the result into separate tracks and tag it correctly. There is software to assist this whole process, like Channel D’s Pure Vinyl, but it is never that quick and easy. There is also the question of how much to tinker with the results in the hope of improving it, via click removal and the like. Personally I tend to the view that most things risk making the sound worse, but there is certainly a case for it, especially with particularly intrusive scratches.

Last week I went to a demo of Plato, a system for ripping vinyl combined with an all-in-one home media playback solution. It comes from the Derby-based company Convert Technologies, formerly known as Entotem. The company has also launched the Red Dot recording service, through which you can get them to rip vinyl or even CDs on your behalf.

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The company showed me its top of the range unit, which is an all-in-one box for storing digital media as well as playing it, and includes a power amplifier which delivers, they say, 25W Class A amplification or 50W Class B. The idea of Class A/B amplification is not new so I am not sure whether there is any secret sauce in the Plato design; however the company also offers a Class B version at a considerably lower price.

The system runs Android customised for the purpose, with a touch screen. There is also a controller app which works best on Android but is also available for Apple iOS with “approx 70% of the functionality”. It includes an ESS Sabre 32 DAC and ADC. Inside is a beefy toroidal tranformer powering the various boards. Around the back is a generous set of inputs and outputs, including MM/MC phono input, 3 additional line inputs, 1 coax and 3 optical digital inputs, 2 optical digital outputs, 1 HDMI output, and 3 USB 2.0 ports.

The digital format can be set up to 24-bit/192 kHz.

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You can pay extra for SSD storage which is pretty pointless from a technical point of view (SSD is much faster, but a conventional hard drive easily fast enough for audio recordign and playback) but would lower the noise level slightly, though the fan is likely to be louder in any case.

Having all the controls functions driven by software enables plenty of features. You can change the phono input from moving coil to moving magnet, vary the capacitance and resistance,  and apply a rumble filter, for example.

Ripping vinyl is a matter of pressing a red button (hence the name of the ripping service). When the audio is played, there is an analogue chain for listening, I was told, but also a “parallel digital path” which captures a sample of the audio and sends it to Gracenote, an online tagging service, for recognition. If you are lucky, you will get the metadata and album artwork automatically retrieved. The system will also separate the tracks for you, taking most of the drudgery out of the ripping process. 

The system does not attempt any click or noise reduction. “We have looked at it, because we write all the software, but most people said ‘don’t do it’,” said Pete Eason, Customer Experience Manager. “It’s not a priority”.

You can export the files to USB storage, so you could do your own additional processing if you wanted. However there is an annoyance: the agreement with Gracenote prohibits the export of the album art. So if you export your files for playback on a phone, for example, you don’t get the art. That’s irritating and there is talk of switching to another metadata supplier to fix it.

The system will stream music from attached USB storage, or over the network using UPnP. I am not a fan of UPnP because it seems less amenable to search, and less reliable, than other systems such as Logitech Media Server, but it should work OK. Internet radio is also provided, via the TuneIn service.

However you cannot access Plato’s storage directly over the network. This makes me wonder if Plato’s engineers would have been better off using Linux rather than Android for their embedded OS, as that would make this trivial to implement.

There is no support for Spotify Connect, which is a shame. You can of course stream to the unit from a phone or laptop using a device such as Google ChromeCast but that is not the same thing, since the quality and consistency of the signal is limited by your phone.

The Red Dot ripping service sounds good for those with plenty of money and little time, especially as it includes a cleaning service, but it is expensive at £10.00 per album and a minimum quantity of 25. Note you could buy the CD for less in many cases.

There is also a limitation in terms of the playback equipment used. It would be too expensive to use a true high-end cartridge and stylus. Red Dot uses “a really decent Pro-Ject Debut Carbon turntable and Ortofon stylus,” according to the FAQ, though they talked about other possible turntables, but always mid-range. That may not equal the equipment you have at home.

I got to ask some awkward questions. Why would anyone want to rip their vinyl, when with Spotify or Apple Music you could just play it from internet?

“There’s a quality issue there,” said marketing guy Ben Timberley. Eason added, “and also you can backup your vinyl. It’s always going to be a pristine original.”

Well, it will not always be a pristine original, but it will always be the same as when it was ripped.

I asked a hypothetical question. Let’s say I submit my rather beaten-up copy of David Bowie’s Ziggy Stardust, and as it happens Red Dot had just ripped someone else’s pristine copy of exactly the same album. Would they rip my scratched copy, or simply give me their existing rip? I would get my crackly one back, I was told. The other copy “belongs to someone else. We are sticking firmly on the side of the law on this one.”

I am not personally convinced that the law is so clear-cut. My records all say “unauthorised … copying of this record prohibited” and “all rights reserved”. On the one hand, there is the question of whether even personal format conversion of a record is strictly legal (though I cannot imagine anyone being pursued for it). On the other hand, since the record represents a personal license to enjoy that particular recording, I am not sure that whether you get back a copy of your record or someone else’s makes any difference.

Red Dot also offers to rip CDs, and here the argument seems even more ridiculous. Since ripping a CD with identical mastering results in an identical file, it would be absurd to re-rip when you already have the file in question. Are LPs any different, even though the imperfections of the format mean that every rip will vary slightly?

Next question: is there a paradox at the heart of this operation, which is that people who love records believe that the analogue chain sounds better than digital, so they are unlikely to want a digital copy? And if they do, why not just buy the digital version?

I got a somewhat garbled response. “That’s one argument but then this is essentially lossless, isn’t it?” said Eason. “You’re getting all the pops, the clicks, the whistles.”

“We’ve got the best DAC in the industry, which is the Sabre DAC,” added Timberley. “If you are going to convert it we’ve got the best piece of kit to do it.” Though I think he meant ADC rather than DAC.

I also suggested that retailers might prefer to buy their own Plato and offer a ripping service, rather than resell Red Dot. Dealers are “too busy” said Timberley, though they might look a a licensing restriction if it became an issue.

What I think

This is not a review and I have not had a chance to try this at home. If you seriously want to rip your vinyl (and I do think there could be good reasons, as I stated above, though hearing pristine pops and clicks is not one of them), then Plato looks like a convenient though expensive choice.

As an all-in-one hi-fi (just add speakers) Plato might also be good, though it looks expensive compared to, say, a NAS, a Raspberry Pi with a DAC, and a decent amplifier. It is hard to value these things without trying them out though.

In the end though, my instinct is that the best way to play records is to play records. I haven’t found record wear much of a problem, especially when you have a large collection.

So I am not sure that Plato is for me, though it does look nice and easy to use.

Table of recommended retail prices (including VAT)

  Vinyl ripping Phono Stage Pre Amp Power Amp
Class B		 Power Amp
Class A 		Price with
1TB HDD		 Price with
2TB HDD		 Price with
1TB SSD
Plato Lite Yes (with external
Phono stage)		 No Yes No No £1899 £1999 £2539
Plato Pre Yes Yes Yes No No   £2400 £2940
Plato
Class B		 Yes Yes Yes Yes No   £2999 £3539
Plato Class A Yes Yes Yes Yes Yes   £3999 £4539
audio, gadgets, hifi

Raspberry Pi does Audio at the Wigwam HiFi Show 2016

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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.”

audio, devialet, hifi

Devialet’s Phantom audio system on show in Barcelona

I was glad to see and hear the French Devialet Phantom system at the Mobile Focus event in Barcelona, just before Mobile World Congress, having missed the company’s recent presentation in London.

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The Phantom is a device that looks like a giant eyeball, and is essentially an active mono wireless DAC and speaker. There are two models, the Phantom which delivers up to 99dB at 1 metre and costs €1690, and the Silver Phantom which delivers up to 105 dB at 1 metre and costs €1990. There is an optional Dialog unit at €299 which is a wi-fi router that creates a private network for the Phantom as well as supporting a guest network designed for music sharing. A Dialog can also control up to 24 Phantoms and is necessary for multi-channel; obviously for stereo you need at least two. An app called Spark runs on iOS, Android or Windows (not Windows Phone) and handles playlists as well as visualising music.

Each Phantom has a midrange unit, a treble unit, and two woofers. It measures 253 x 255 x 343mm and weighs 11 kg.

My encounter with Phantom did not get off to a good start. I am allergic to misleading jargon, and the pitch the Davialet representative made to me was confusing to say the least. “Digital chops up the sound,” he told me; but with hybrid technology Devialet was able to reproduce the purity of analogue sound. I observed that every DAC in the world is able to decode digital formats to analogue sound, and we had some difficulty progressing to what exactly is different about Devialet’s approach.

The case for the Phantom is not helped by the over-the-top language in the brochure, which modestly claims “the best sound in the world” and under a heading “IN TECHNICAL TERMS” promises Zero distortion, Zero background noise and Zero  impedance.

The system was playing Hotel California by the Eagles when I was there. I know the sound of this album well and it sounded boomy and unpleasant, though it is difficult to get good sound on a stand in a busy exhibition so I make generous allowance for that.

I did get a copy of a white paper which offers a bit more information. There are several technologies involved.

The first is what Devialet called ADH (Analog/Digital Hybrid). This combines class A amplification with the efficiency of class D. The way Devialet puts it is that several class D amplifiers act as slaves to the class A amplifier, so that the class D amplifiers provide the power while the class A amplifer the control.

A Texas Instruments PCM179x DAC is positioned next to the amplifier to minimise any loss between the two.

Next comes SAM (Speaker Active Matching) which processes the audio to compensate for the characteristics of the drive units. This “takes place ahead of the DAC and power amplifier section” according to the paper, so you could think of it as a kind of digital pre-amplifier. SAM has “a mathematical model of the complete drive unit, accounting for the electrical, mechanical and acoustical behaviour.”

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A third feature has the name HBI (Heart Bass Implosion). This tackles the tricky problem of reproducing deep bass with a small enclosure. The idea is to use a sealed box design for high efficiency at the lowest frequencies, a driver with long 26mm excursion (the difference between the foremost and backmost position of the driver) in order to move more air, and to use two symmetric drivers to cancel mechanical vibrations.

This does result in high maximum air pressure inside the enclosure, up to 174dB SPL according to Devialet’s paper. Most drivers collapsed in this environment, so Devialiet designed its own woofer.

Finally Devialet’s engineers figured that a sphere is the ideal shape for producing sound without “diffraction loss”.

The result, according to the specs, is 16Hz to 25kHz +- 2dB, and 20Hz to 20kHz +- 0.5dB which is impressive for a speaker system.

The problem with such measurements is that they typically taken in an anechoic chamber whereas actual listening rooms have all sorts of resonances that result in a much less accurate sound.

Does Devialet’s Phantom system sound as good as a more traditional system at its price level? That is the question which interests me; if I get an opportunity to try it out I will be sure to report back.

audio, hifi

Playing native DSD with Raspberry Pi 2 and Volumio

There are many intriguing debates within the world of audio, and one which has long interested me concerns DSD (Direct Stream Digital). This is an alternative technology for converting and recovering sound from digital storage. The more common PCM (Pulse Code Modulation) works by sampling sound at very short intervals and recording its volume. By contrast DSD records the difference between one sample and the next, sampling at an even greater frequency to compensate for the fact that it only captures a single bit of data in each sample (ie on or off). For example the standard used by CD is:

16-bit precision, 44.1 kHz sampling rate

and by SACD (a DSD format):

1-bit precision, 2.8224 MHz sampling rate

The SACD was introduced by Philips and Sony in 1999 as an upgrade to CD, since it is a higher resolution format cable of a dynamic range of 120 dB and frequency response up to 100 kHz. It was an effort, like the PCM-based DVD Audio, to convince the public that the CD is not good enough for the best quality sound.

SACD was largely unsuccessful, mainly because there was not really any dissatisfaction with CD quality among the general public, and even some experts argue that CD quality already exceeds what is required to be good enough for human hearing.

That said, SACD was popular in the niche audiophile community , more so than DVD Audio. Some listeners feel that SACD and DSD results in a more natural sound, and believe that PCM has some inherent harshness, even at higher-than-CD resolution. Enthusiasts say that DSD stands for “Doesn’t sound digital”. For this reason, there is a regular stream of new SACD releases even today, and DSD downloads are also available from sites like Native DSD Music and Blue Coast Records. Some DSD downloads are at higher resolution than SACD – Double-rate or Quad-Rate.

The resurgence of DSD has been accompanied by increasing availability of DSD DACs (Digital to Analogue Converters). While these tend to be more expensive than PCM-only DACs, prices have come down and a quick eBay search will find one from under £100.

There are several complications in the DSD vs PCM debate. While DSD is a reasonable format for storing digital audio, it is poor for processing audio, so many SACDs or DSD downloads have been converted to and from PCM at some point in their production history. If PCM really introduces harshness, it is presumably too late by the time it gets to DSD. That said, it is possible to find some examples that are captured straight to DSD; this can work well for live recording.

Another complication is that some consumer audio equipment converts DSD to PCM internally, to enable features like bass management.

Is there any value in pure DSD? I wanted to try it, preferably with DSD files rather than simply with SACD, since this is much easier for experimenting with different formats and conversions as well as enabling Double DSD and higher. Unfortunately SACD is rather hard to rip, though there is a way if you have the right early model of Sony PlayStation 3.

The first step was to get a DSD-capable DAC. I picked the Teac 301 which is a high quality design at a reasonable price. But how to get DSD to the DAC? Most DSD DACs support a feature called DSD over PCM (DoP), which conveys the DSD signal in a PCM-format wrapper. DoP is not a conversion to and from PCM, it merely looks like PCM for better compatibility with existing playback software.

Next, I used a Raspberry Pi 2 supplied by Element14 (cost around £25.00) and installed Volumio, a pre-built version of Linux which includes an audio streamer and web-based user interface. You download Volumio as a single file which you burn onto a micro SD card using a utility such as Win32DiskImager. Then you plug the card into the Pi, connect to a home network via Ethernet and to a DAC via USB, and power on.

After a minute or two I could connect to Volumio using a web browser.

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My music is stored mostly in FLAC format but with a few DSD files in Sony’s DSF (Digital Storage Facility) format, and located on a Synology NAS (Network Attached Storage). In Volumio’s menu I went to Library and mounted the network share containing the media. Next, I tried to play some music. PCM worked, but not DSD. I changed the playback settings to enable DoP:

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Success: My DSD files play perfectly:

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If you squint at this image you will see that the 5.6 MHz light is illuminated, indicating that the DAC is processing Double DSD.

It sounds lovely, but is it any better than the more convenient PCM format? I am sceptical, but intend to try some experiments, using a forthcoming audio show to find some willing listeners.

That aside, I am impressed with the capability of the Raspberry Pi for enabling a simple and cost-effective means of playing DSD over the network, although with the assistance of an external DAC. It plays PCM formats too of course, and with Volumio is easily controlled using a mobile device, thanks to the touch-friendly web UI.

audio, hifi, retro

Fun with amplifiers: classic Naim versus modern Yamaha integrated

1 Comment

Every year in an English country hotel near Melton Mowbray a strange but endearing event takes place.

Called variously the HiFi Wigwam Show (after the forum that runs it) or the Scalford HiFi Show (after the hotel where it takes place), this is a show where most of the exhibitors are enthusiasts rather than dealers, and the kit on show includes much that is old, unavailable or home-made – like these stacked Quad 57s from the Sixties.

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I turned up at Scalford with a simple experiment in mind. Take a classic pre-power amplifier from thirty years ago and compare it to a modern, budget, integrated amplifier. What kind of differences will be heard?

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The classic amplifier is a Naim 32.5 preamp powered by a Hi-Cap power supply, and a 250 power amplifier. Price back in 1984 in the region of £3500. The Naim was serviced around five years ago to replace old or failing electrolytic and tantalum capacitors.

The integrated is a Yamaha AS500 80w+80w amplifier currently on sale for around £230.

The source is a Logitech Media Server (Squeezebox Server) with a Squeezebox Touch modified to work with high resolution audio up to 24/192, and a Teac UD-H01 DAC. Speakers were Quad 11L, occasionally substituted with Linn Kans for a traditional Linn/Naim combination. A BK Electronics sub-woofer was on at a low level to supplement the bass.

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A QED MA19 switchbox was used to switch instantly between the two amplifiers. Naim NAC A4 cable was used throughout.

Disclaimer: this was not intended as a scientific investigation. Level matching was done by ear, and there were several aspects of the setup that were sub-optimal. The system was in a small hotel bedroom (as you can see by the headrest which forms the backdrop to the system) and thrown together quickly.

Still, the Naim amplifier is both highly regarded by many audiophiles, and also considered somewhat coloured, this failing more than mitigated by its pace and drive. The Yamaha won awards as a good budget amplifier but is not really anything special; however it has the benefit of modern electronics. These two amplifiers are very different both in age and (you would think) character.

A benefit of the setup was that both amplifiers were always on. Unless you knew the position of the switches and how they were wired, you could not tell which was playing. It was irresistible; when visitors asked which was playing I switched between them and said, you tell me.

Again, this was not science, and I have no tally of the results. Some visitors confidently identified the Naim and were correct, and an approximately equal number were incorrect. Some said they simply could not hear a difference, and two or three times I had to prove that the switchbox was working by twiddling the controls. A small boy who probably had the best hearing of all the visitors declared that there was no difference.

Note that I did reveal the identity of the amplifiers at regular intervals, so listeners typically listened sighted after listening blind.

Of those who expressed a preference, the Yamaha and Naim were each preferred equally often. Some said the Yamaha was slightly brighter (I agree with this).

There were two or three who expressed a strong preference for the Naim, but the consensus view was that the amplifiers sounded more alike than had been expected.

The sound was also pretty good. “I would be happy with either” was a common remark. I would have preferred to use high-end speakers, but the Quads proved delightfully transparent. Most visitors who heard both preferred the Quads to the Kans, which sounded thin and boxy in comparison, though I do wonder if after thirty years the crossover electronics in the Kans may need attention. It was easy to hear the difference between high quality and low quality sources. I used some of the high-resolution files which Linn kindly gave away as samples for Christmas 2013, along with other material.

A few reactions:

Tony L: The most amusing room for me was the Naim 32.5 / HiCap / 250 blind-test vs. the Yamaha AS500. That was great fun, and yes, I picked the AS500 as better. Twice. As did another ex-32.5/Hicap/250 owning friend. Ok it was through a nice easy to drive pair of Quad 11Ls, but you’d be amazed by how close they sounded!

YNWOAN: I heard the Yamaha/Naim demo and had no difficulty hearing a difference between the two with the Yamaha sounding rather ‘thin’ – even at the low levels used.

Pete the Feet: How cruel can a man be? Pitching a recently serviced Naim 32.5, Hicap and NAP250 against a paltry Yamaha £250 integrated. Not much difference but the Yamaha had the edge.

Some felt that the Naim was compromised by the stacking of the power supply and pre-amp on the power amp. There was no hum and I am sceptical of the difference moving them apart, or using acoustic tables, might have made; but of course it is possible. Another interesting thing to test would be the impact of the switchbox itself, though again I would be surprised if this is significant.

How much should you spend on an amplifier? Should all competent amplifiers sound the same? These are questions that interest me. I set up this experiment with no particular expectations, but the experience does make me wonder whether we worry too much about amplification, given that other parts of the audio chain introduce far more distortion (particularly transducers: microphones and loudspeakers).

A more rigorous experiment than mine came to similar conclusions:

How can it be possible that a basic system with such a price difference against the  reference” one, poorly placed, using the cheapest signal cables found, couldn’t be distinguished from the more expensive one?

And, most of it all, how come the cheap system was chosen by so many people as the best sounding of the two?

Shouldn’t the differences be so evident that it’d be a child’s game to pick the best?

Well, we think that each can reach to its own conclusion…

One further comment though. I love that Naim amplifier, and do not personally find something like the AS500 a satisfactory replacement, despite the convenience of a remote control. Is it just that the classic retro looks, high quality workmanship and solid construction convince my brain into hearing more convincing music reproduction, provided I know that it is playing? Or are there audio subtleties that cannot easily be recognised by quick switching?

Unfortunately the audio industry has such fear of blind testing that these questions are not investigated as often or as thoroughly as some of us would like.