It's a wet Sunday afternoon and I've discovered an alternate universe in a hotel outside Melton Mowbray. At least I've got a guidebook, although the leaflet headlined "2015 HiFi Wigwam Show" might as well be in Biblical Aramaic for all the sense it makes. "Home-built passive pre-amp feeding very unusual VRR monoblock power amps and rounded off with Tannoy Cheviots." "Software-based room correction and linear phase crossovers feeding six Hypex amps powering DIY sealed box three-way speakers." "Tri-amped with classic Pye HF25, PF91 and HF 5/8, stacked Quad ESL57s with lonophone plasma supertweeters."

But if the guidebook seems odd, it's nothing compared to what's actually happening in the hotel. The HiFi Wigwam Show — one of the premier annual gatherings for Britain's audiophiles — has taken over the whole building. Every guest room contains a man — it's always a man — with a hi-fi system he's brought from home. People go from room to room, listening. Pinned to the walls of the corridors, you occasionally see a small ad written in the same impenetrable language as the guidebook. "Wanted: Nordost Valhalla speaker cables spades both ends," reads one. "Please call."

You may think of yourself as someone with an interest in hi-fi, who believes that the music you love deserves to be heard in decent sound quality. Perhaps you spent a few hundred quid on an amp and speakers, or a Sonos system. Perhaps you upgraded the earbuds that came with your phone for a pair of Beats headphones. Or perhaps you've junked your CDs and turned your nose up at digital downloads in favour of a return to vinyl, confident that it sounds "so much warmer".

But you're not an audiophile. By the standards of the exhibitors at HiFi Wigwam, you're a part-timer, a dilettante, you're one step away from the dog on the HMV logo, your idiot brain transfixed by the muffled sound coming from a wax cylinder. There's a guy in one room who's eschewed hi-fi equipment altogether in favour of playing music off the huge reel-to-reel tape machines you get in recording studios. There are people here who build their own speakers and CD players. There are "modders", men whose immediate impulse upon buying a £3,000 amplifier is to rip off the back and set about it with a soldering iron, confident they can make it better.

***

In a room off the hotel lobby, I find Steve, a building contractor from Essex, who has devoted his spare time to assembling the most deranged-looking hi-fi system I've ever seen.

The speakers have something resembling the horn from an old gramophone on top of them: they're called Acapella High Violons and you have to play music through them continually for 14 days to "break them in". They sell for £40,000 a pair. (This makes them Acapella's entry-level model: its top-of-the-range speaker costs around £350,000, looks like someone nailed two tubas to a mid-Eighties Habitat shelving unit and can only be used in rooms over 131sq ft.)

His turntable has two platters, one on top of the other. The bottom one spins round in the opposite direction to the one on top: apparently it's designed on the same engineering principle as the counter-rotating blade of a helicopter. There are only two in the UK, possibly because its recommended retail price is £30,000. It's sitting on top of something that looks remarkably like a Black & Decker Workmate bench. It turns out that this is because it is a Black & Decker Workmate bench.

Someone hands Steve an album and he puts it on, and it becomes apparent that, however crazy his system looks, that's nothing compared to how it sounds.

The old line about great hi-fi making it feel like the band's in the room with you isn't quite right. It doesn't sound like live music: it sounds better. Clearer, more pure. The weirdest thing is that the music doesn't appear to be coming out of the speakers: it seems to be happening in a space just in front of you. It feels like it's in 3D: you could walk around it, you could reach out and touch it. It's astonishing.

And that's the thing about audiophiles. You can, if you're so inclined, mock their nerdiness; if that's your wont, then there are plenty of people here from geek central casting, including a man wearing a T-shirt that reads: "THERE'S A NAME FOR PEOPLE WITHOUT BEARDS: WOMEN".

You can look askance at the kind of things that get them riled up – if you want to start a massive row among high-end hi-fi buffs, if you want to turn the HiFi Wigwam Show's atmosphere of beery bonhomie into one of murderous fury, get them on the subject of whether the cables used to connect hi-fi components make a difference to the sound. You can wonder aloud whether some of them aren't more interested in sound waves and lonophone plasma supertweeters and shiny boxes from Japan and Germany than they are in music.

And you can stand there with your mouth hanging open and your finger twirling by your temple when you find out how much they'll pay for a CD player or a pair of speakers – however much they tell you that good sound is not about how much you spend, but how carefully you match your components, you never seem to meet an audiophile who hasn't lavished thousands of pounds on their obsession.

But if you've got functioning ears and a love of music, you can't help but boggle at the sound their equipment can make.

I listen to this bizarrely tangible music and I look at Steve. And I can't decide whether he's a kind of epicurean genius, dedicated to something really noble – presenting great art in the best possible way – or a total fruitcake.

Whichever it is, the music business would currently like us all to be at least a bit more like him. Sound quality is a hot topic. Record companies are hoping to shill us high-definition, better-than-CD-quality downloads. Neil Young is trying to flog us his high-resolution Pono digital player. That weird conglomeration of pop stars who got onstage in New York in March and started carrying on as if they'd discovered a way to cure all known diseases were trying to interest the public in Tidal, a music-streaming service that offers better sound quality than Spotify, for a £20-a-month subscription fee.

Of course they are – there's theoretically a lot of money in it. If record companies can convince people they need high-definition downloads, then it might be the CD all over again. It means music fans re-buying their entire record collections at a premium price. If you find it odd that pop stars are suddenly so interested in sound quality – after all, you never heard The Beatles complaining that listening to their music on a transistor radio or a crappy old Dansette was somehow disrespecting their artistry – well, that's where the money is these days. There's less cash in music itself than in the means by which music is distributed and played.

The best of luck to them. They're going to need it.

For the past 40 years, every major technological advance in hi-fi that's caught on has been about convenience rather than sound, such as the Walkman, the MP3, the iPod and streaming. Even the CD was marketed more on its size and alleged indestructibility. The ones that tried to tempt the public with sound alone were the ones that withered and died and now languish forgotten: Quadraphonic, Super Audio CD, DVD-A, Blu-Ray Audio. The general public, it seems, couldn't give a flying one about sound.

All of which makes audiophiles something of a band apart. Their world feels deeply arcane, even by the standards of what you might call luxe pursuits. There are TV programmes devoted to drooling over supercars. There's always space in the Sunday supplements for articles about fine wine. Turn the pages of a men's magazine such as this one and you'll find stuff about suits and shoes and watches no normal person would dream of buying. It's aspirational.

But the mainstream media takes no interest in audiophiles. Everyone knows the Bugatti Veyron, but no one outside of the audiophile community has heard of the serious high-end hi-fi manufacturers: Audio Note, Puresound, Advantage, Nagra.

That may be because most of those other pursuits are about outward show: if you drive a Bugatti Veyron or wear a Rolex Oyster, you're making a very public statement about yourself. But a high-end hi-fi isn't a public statement. It's squirrelled away somewhere in your house, not on open display, unless you dismantle it and haul it up to something like the HiFi Wigwam Show, and even then only other audiophiles – and the odd nosey hack from Esquire – will see it.

The convivial atmosphere at the HiFi Wigwam Show notwithstanding, being an audiophile seems an oddly solitary pursuit.

There are those happy to invite their non-audiophile mates around for a listening session, but they seem to be outnumbered by those who keep their interest to themselves and the other members of their tribe. Steve tells me he thinks it attracts "people who are a little bit introspective, a little bit shy, if you want to generalise". Others talk about it as being like a religion: you wouldn't go around trying to foist it on your non-believing friends.

***

"It's sort of a secret," says Jason, a 46-year-old teacher with a West Country accent, a rather serious manner and a "six- figure" system. He claims to "eat, think and breathe hi-fi", but even so, he says, "I never tell anyone at work. They wouldn't understand." He says that very emphatically, and he may have a point.

Worried that something he calls "dirty" electricity will affect the sound his system produces, Jason has had his home rewired – his hi-fi is on a separate mains ring to the rest of the house, running off the "purest electricity possible". "It's quite a lonely road in some ways," he says. "Because when you're listening, you're in your room, it's just about you and the music."

It's an obsession they even shield from those closest to them. I keep hearing about audiophile wives who share their husband's passion – everyone I speak to seems to know another audiophile whose wife enjoys nothing more than discussing the finer points of software room correction – but I never actually meet one. I start to wonder if it's a kind of urban myth. In fact, keeping your partner in the dark about your hobby seems as much of an audiophile skill as being able to spot the sonic difference between two different brands of speaker cable.

"It's the audiophile's biggest fear, isn't it?" grins James, the immensely affable founder of HiFi Wigwam, an online forum that begat the show. "They die and then their wives sell their hi-fi equipment for what they told them it cost." Even Trevor, a retired engineer, who's gone to the extreme of building his own listening room – a windowless, soundproofed, acoustically treated, freestanding structure within a barn next to his East Anglia home, complete with a handmade 300lb door filled with building sand – suggests his wife, who presumably got an inkling something was up when the builders arrived, isn't entirely au fait with what goes on inside it.

"It's something my wife doesn't know anything about," he says, when I pay him a visit. "She would absolutely pass out if she had any idea how much money I've spent." He used an inheritance from an aunt, he says; he didn't dip into the household budget. His hi-fi equipment is insured for £75,000. As if to prove its worth it, he shuts his handmade door, dims the lights and puts on a CD by Oscar Peterson. It's the whole astonishing 3D, tangible-music experience again. I say so and Trevor nods happily. That means he's created a good soundstage, he says.

Like every audiophile I speak to, Trevor seems a really nice guy. Normal. Dotes on his granddaughter, talks fascinatingly about stuff that isn't hi-fi: the cultural differences between Britain and the US, where he was born; his time in the forces – he served in Vietnam towards the end of the war. You'd like him. Maybe I got lucky: apparently, there's some real headcases out there, people who, as Trevor puts it, "you wouldn't want to bring home to meet your mother".

But it all begs the question: what sets an otherwise normal man off on a path that leads them to commission a handmade 300lb door filled with sand or rewire their house, in pursuit of sound quality?

Some audiophiles talk about a Damascene moment: a post-pub visit to a friend's house where they heard music they loved played on really good equipment and never really recovered. Laurie, a 65-year-old "semi-retired" writer from Suffolk, tells me that as a kid, his family were poor: they couldn't afford a record player, so he had to make do with a wind-up gramophone and a selection of Gracie Fields 78s someone had bequeathed them. He doesn't explicitly make the connection between this and what he calls a "slightly ridiculous" obsession with high-end hi-fi in later life, but you do the amateur psychology.

***

But most of them don't have a story like that.

When you ask what got them into high-end hi-fi and all its trappings, they talk vaguely about loving music when they were a child or being fascinated by the family record player. Well, yeah, I think, but so was I, so were loads of people I know, and they've managed to get by without rewiring the house or buying bits of plastic that ensure their speaker cables don't touch the floor in the belief that it affects the sound. Perhaps there's something else, something deeper.

James from HiFi Wigwam is not a man much given to mysticism – he's funny and self-deprecating and tells me that the best upgrade you can buy for your equipment is "a couple of bottles of wine" – but he has a theory that audiophiles might be wired differently to everyone else. "You know how you get super-tasters for wine and people who have particularly good palates for tasting food? I wonder if our hearing might be like that, and that's why we get drawn into it."

Maybe he's right. Maybe audiophiles have some kind of weird heightened superpower hearing. And maybe it's sometimes a burden. Trevor tells me he finds it hard to listen to music that's badly recorded, no matter how great the actual music is. "Amy Winehouse, amazing voice, but Back to Black… that's a terrible-sounding album." He recently went to a gig by fabled jazz pianist Keith Jarrett. "Ruined," he says. "Ruined by the sound reinforcement in the hall."

James tells me he sometimes feels he's not listening to music, but to his hi-fi system: he's a fan of Kraftwerk and Joy Division, but finds he's been buying "plinky-plonky jazz" because it shows off his equipment. "I would never," he says heavily, "have bought a Diana Krall album unless I was into hi-fi. But play a Diana Krall album on my system…" He blows out his cheeks. "Bloody hell."

People listening to music they don't like, people who find themselves unable to listen to music they like. As I said, it's an alternate universe. It has its own language and its own tribes, not least the box-swappers: audiophiles whose quest for elusive perfect sound quality leads them to constantly upgrade or alter their hi-fi, buying and selling equipment with a dizzying frequency.

It has its own controversies, a lot of which seem to stem from the fact that sound quality is a completely subjective thing: there's no way of meaningfully measuring it, so if you think something improves your system, then, well, it does.

Hence the ideas and products peddled by Peter Belt, a former electronics engineer who variously advocates freezing CDs before you play them, colouring in the edge of your albums and the fuses in your plugs with a violet marker, ensuring that all the leads on your hi-fi system are white – that's not a euphemism for something technical, he means coloured white – and the use of a series of mysterious creams. You rub these into your hi-fi components and — get this — the magnetic strips on your credit and debit cards to improve "energy patterns" and achieve better sound quality. A lot of the audiophiles I speak to understandably think Belt is a raving nutter, or, worse, a snake oil salesman, but even so, his adherents aren't hard to find. "I've got some of his products," says Jason. "Do they work? I wouldn't be paying money for them if I didn't think they did.

And it has its own curious celebrities. There's Roman "The Cat" Bessnow, a Russian-born, US-based blogger acclaimed in some quarters as "the world's most obsessed audiophile", whose bafflingly designed website mixes quotes from Thomas Mann with hugely opinionated screeds written in Seventies comedy-show pidgin English: "I have an excremental tone arm".

There's the group of hugely wealthy Greek businessmen who call themselves the Audiophile Club of Athens, the subject of a much-discussed YouTube documentary, with whom Laurie has had dealings. He once designed a small piece of hi-fi equipment of his own: the Audiophile Club of Athens ordered several from him, then wrote him a letter of congratulations, which also noted they'd discovered that its sound quality was improved if you hung it from the ceiling on a piece of cotton thread.

And there is Peter Qvortrup, a Danish former hi-fi retailer turned maverick hi-fi manufacturer who runs his company, Audio Note, from a shop in Hove that appears from the outside to have closed down years ago – the window display is a cobwebbed mess of empty wine and tequila bottles.

The equipment Audio Note makes is both hugely well-respected and eye-wateringly expensive: don't even think about the top-of-their range unless you're an oligarch or a Far Eastern multimillionaire. It takes about five minutes in his company to see why Qvortup's reputation precedes him in the audiophile world. He quotes Kierkegaard and Einstein, seems to think that more or less every other hi-fi manufacturer in the world is doing everything wrong, tells me he believes that the best speakers were made in the Thirties and announces that he spends £7,500 a year on champagne. He is richly, riotously entertaining company, but he is deadly serious about hi-fi. None of this I-don't-want-to-foist-my-religion-on–unbelievers stuff from him. He's positively evangelical.

"If your article is to have any journalistic validity at all," he says, thumping the table for emphasis, "it's important to impress upon people that if you run around listening to music on one of these" – he stabs at my iPhone – "with headphones the size of a pea, the price for that is very considerable in terms of your musical enjoyment and understanding. And then, if you think about music developing over the next 100 years in order to satisfy the requirements of things like this" – another disgusted look at the iPhone – "then we're going to end up with music that's absolutely inane and useless."

On the one hand: well he would say that, wouldn't he? It's his business to sell hugely expensive hi-fi. But on the other, there's the uneasy feeling he might have a point. Take dubstep. Not the good stuff: the awful, noisy, bleached-white, funk-free variant that sounds like a giant robotic moron stamping on the face of humanity, the one that's popular with hideous, gurning American frat boys. One of the reasons posited for its success was that most people hear music via their computers these days and it sounded good coming out of tinny laptop speakers: there were no subtleties in the music to lose.

***

Sometimes, says James from HiFi Wigwam, being an audiophile feels less like a hobby than having a weird illness, like obsessive-compulsive disorder or something: you know what you're doing is a bit daft, but you can't stop yourself.

The audiophiles I speak to keep insisting that they've got their hi-fis to sound just how they want them, they won't be buying any more equipment, they're as close to perfection as they're going to get. They say that and then they say the word "but" – there's always another box, another tweak, something else that might get them a little closer. Laurie tells me he's planning to downscale his system, but, with the best will in the world, his plan doesn't seem to be going terribly well. "I've got this caveat: what if we move house? I might need another amplifier. Or I might need a spare. I've got two spare amps, you know, just in case."

James says that his hi-fi obsession recently led to a kind of existential crisis. He was at a show in Munich and he heard a pair of Magico speakers that cost $600,000.

"They played a Dead Can Dance track on them, and…" His voice trails off and he sticks his hand out. "Look, the hairs on the back of my arms are standing up just thinking about it. The room was just full of this sound. It was immaculate. Immaculate. I walked out and said, 'Well, that's it. That's the sound I want.' And I'll never be able to afford them. So I've just blown my hobby forever."

But that was a year ago, and a huge pair of speakers still dominates the living room of his terraced house.

He asks me if I want to hear something on his system. I choose "To Here Knows When", the 1991 single by My Bloody Valentine that Brian Eno described as "the vaguest music ever made". When it was released, people kept taking it back to the shops, convinced that there was something wrong with the record they'd bought: surely it wasn't meant to sound like that, with its beautiful sleepy-eyed melody almost drowned out by layers of churning, woozy noise. I've listened to it obsessively for 25 years, trying to get to the bottom of what the band thought they were doing. In Steve's front room, I feel like I'm sitting in the middle of the song, the guitars arcing around me. It's overwhelming. And once again, all the downsides of audiophile addiction – the ridiculous financial excesses, the mystical woo, the obsessive behaviour – seem to evaporate.

Who wouldn't want music to sound this enveloping, this enrapturing? Would I spend £40,000 on a set of speakers? Would I rewire my house? Would I build a freestanding structure in a nearby barn? Of course I wouldn't. But there's a part of me that knows precisely why they do and thinks the rest of us don't know what we're missing.

***

MORE LONG READS:

How 6 Music Defined The Music We Listen To Today

Alone: How It Feels To Spend A Week In Total Isolation

Will Self's Music Festival Hell

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