DIY Audio: Putting the power in your hands

  • Mars is a big fan of tube designs’ simplicity and low component count.
  • Salvage, scrounge, repurpose: Mars (below, pointing out still usable high-grade polystyrene capacitors to author Doman) can’t believe how much stuff we dump.
  • Karel Mars winds a transformer on a machine that had been “just lying around”.
  • Rudi Marloth says the beauty of DIY is that you can fix something… or make it better.
Date:16 September 2013 Author: Anthony Doman Tags:, , , , ,

Putting the power in your hands. DIY is alive and making waves in the home audio universe. Pictures by Sean Woods

Money, the Beatles sang, can’t buy love. For everything else, the consumer society promises a solution. (Well, perhaps not everything: no amount of money, apparently, can buy South Africa a cricket World Cup title.)

Many millions of record sales later, the Fab Four would probably have agreed that the music business – specifically audio – is more relentlessly consumerist than most. With options ranging from pocket-sized devices capable of storing entire music and video libraries to otherworldly works of technological art costing millions, the sound industry is big money personified. Pay up and you can take your sound with you, play it as loud as you like, keep it personal or stream it throughout the home.

There would appear to be no space for the home hobbyist – certainly not for the kind of equipment built by Popular Mechanics readers in days gone by. Even a cursory riffle through the PM annals turns up the likes of “Compact hi-quality multi-purpose four-tube AC-DC amplifier”, “Apartment-size hi-fi system makes music live” and so on, often accompanied by a picture of a father (invariably pipe-smoking) and son tinkering away, or husband showing off to a proud wife. What happened?

Technology, industry and commerce, that’s what. Is that it, then? Has cheap, ubiquitous technology made DIY audio redundant? No way, say two confirmed DIY nuts that design DIY amplifier kits right here in South Africa. They operate in a field that is sprinkled with some revered locals – audio enthusiasts go misty-eyed at the mere mention of names such as Alan Hobkirk, Johan Potgieter, Schalk Havenga and Daan Jacobs – but with a twist.

Whereas much of the focus has usually been on creating limited runs of exclusive equipment, a completely different idea is being put out there: you don’t have to buy great sound in a shop – and we’ll help you build it yourself.

Pushing The envelope
Rudi Marloth built everything in his home system except for the CD player and digitalto-analogue converter. Let’s see: that makes it a DIY turntable, phono stage, preamplifier, amplifiers and speakers. Oh yes, and cables.

The impressive thing is not just how good it sounds. It’s how good it looks. The aesthetics vibe nicely (er, well, mostly…) with the dark wood and organic finishes in Marloth’s home in Greenside, Gauteng.

It’s in the field, of amplification, particularly, that Marloth has been making waves. His own takes on established designs, disseminated pretty much by enthusiastic word of mouth, have set local audiophiles chattering, most notably in the online community

For Marloth, audio design is a hobby. After all, he has a proper day job as a consultant in the area of innovation for a global IT company. Currently, the object is to spread the word by developing and marketing kits at prices aimed at recouping costs rather than turning a profit.

Marloth learned the value of DIY early. “I started when I was about 12. There was no way you could actually build anything then. I was given a B&O and the first thing I was taught was to fix things. I never studied electronics. I got concepts, ideas.” It helped having an electrical engineer as a father: “That was a huge advantage.”

He developed his knowledge through tinkering with Daan Jacobs’ beefy (but often temperamental) RS Electronics amps in the ‘70s. “He had an amp called the Classic. It was a copy of a design by [high-end British audio company] Naim… there was a [US audio giant David] Hafler copy… you could get the performance of big names at a really affordable price.

“In the process, you learned so much.” It was inevitable that the tinkering would grow into redesigning.

He acknowledges the disadvantages of the one-man band compared with the R & D armies of big organisations. But there is a flip side to this: “The accounting department is always looking to cut costs. And they have to ensure that things can be done in a cost-effective way on the production line.”

In any case, DIY is not about the money – at least, not just about the money – says friend and fellow DIY nut Mike Mutavdzic. “It’s cheap to buy today. It’s safe to say you can access a computer for up to a quarter of the price you can build a device.

“But it is when you switch on that thing you have built and it does not blow up… that is what drives most of these guys absolutely insane.”

“The beauty of DIY is that you can change things infinitely,” Marloth says. “You can make it different or better,” he says.

“You can fix something yourself.”

His designs range from moving magnet and moving coil phono stages for vinyl replay, costing about R600, to a preamp at around the same price and chip-based amplifiers at about R700. More complex units – potentially costing several thousand rand to complete – are available.

If not money, then what drives DIY? The big drivers back in the heyday of DIY were affordability and a simple lack of access to decent equipment. Mutavdzic started modifying speaker kits in his native Yugoslavia, when “technologically speaking… some people stood on the Moon while others were still using oxen”.

If anything, thanks to the Internet information explosion, the thinking of top designers is reaching a wider and wider audience. At the same time, there’s a danger of information overload – never mind physical danger to the enthusiastic but unskilled.

“If you are doing valve equipment, you could be working with 250V DC and more. It bites,” says Marloth. “But then again… we work with 250 V AC every day. It’s all to do with the human perception of danger.

“At the end of the day, somebody who has never before held a soldering iron can make a pretty decent product.”

Perhaps the most valuable lesson DIYers learn is, says Marloth, the ability to look beyond everything they have been taught. “In fact, beyond their own limitations.”

“I call them,” says Mutavdzic, “the enlightened.”

Looking back
Karel Mars’ rambling, equipment-filled home in Paarl bears testimony to his passions for music and sustainability. The usually laid-back Mars becomes almost animated when the talk turns to re-using, repurposing, re-inventing and reproducing (musically speaking, of course).

Vacuum tubes – valves, in British parlance – are the basis of his designs. There are still huge stocks of existing tubes, though items such as the original legendary Western Electric 300B triode dating back to the 1920s are now rare almost to the point of extinction. Yet there is a burgeoning industry in new tubes, with Chinese manufacturers leading the way in both massmarket and specialists designs.

Despite his focus on a technology that was already in decline when Studebakers still roamed the Earth, Mars freely admits to loving how modern tech is able to help designers.

“In the old days, you had an idea, rolled the transformers, and then listened to it,” he says. “Today we have computer simulations. You just move a slider to change the parameters. It’s so much easier today to do one-offs or to prototype.” (In keeping with his sustainability leanings, he is a huge fan of the Open Source movement.)

Mars builds, repairs and restores tube audio amplification for domestic and stage use as well as designing DIY tube kits. If you’re a fan of local musicians, it’s quite likely that you have heard his work. But, he cautions, the two fields are very different. “Amps for music and amps for hi-fi may use the same technology, but they are worlds apart.” Why tubes?

His answer is what you’d expect of a romantic: “The sound of vacuum tubes always charmed me.” That’s hardly surprising, given that he grew up in the Beatles era, when a Vox AC30 was regarded as big-time amplification. “There was a time I had at least one AC30 a week in the workshop,” he says. He is hoping to ramp up production of his own design, which makes more than a passing nod in the direction of the Fender tweed guitar amp.

Besides the sound of tubes, it’s the old-school simplicity of tube designs that grips him. “Four resistors, two tubes, three capacitors and you’ve got an amp,” he says. “Excluding the 5 transformers, of course.”

Different design imperatives play their part, too. “In most solid state designs, negative feedback [to keep distortion under control] is more or less a given. Inevitably there is a time delay, even if it is almost the speed of light. If you have NFB, something disappears.”

Mars also provides strong evidence, like Rudi Marloth’s, of the effect of parental influence. His machine-builder father built bottle- and crate- washing machines for the wine industry. “He had to think things over in 3D. And he had to have a good grasp of electrical principles.”

Who builds a DIY amp? “Mostly professional people, middle- aged. People in the music industry generally don’t have money!” Fact is, although tube designs have a low component count they involve plenty of hardware and usually need bespoke transformers. Good ones weigh a ton and cost accordingly.

“Of course, you do have your up-and-coming young professionals… they have money. They want something good. And there is a retro movement. A custom-built amp counts for something in that world. ‘I basically offer a workshop environment where the build can be supervised. It’s about skills transferral, really.”

For the tube DIYer, safety is arguably even more of a concern than when building solid-state. Several hundred volts of DC are not unusual. Mars is philosophical about this. “A tube amp is dangerous only once it is plugged in, and there are basic safety precautions, such as putting an incandescent lamp in series with your amp the first time you switch it on.”

A “typical first amp” tube build would run about R4 000. Using EL 84 or 6V6 tubes in super-clean triode or more efficient push-pull mode, it would provide up to 15 watts per channel from no more than about a dozen components. And how’s this for blending the old and the new: “You could play your iPod or laptop through it,” says Mars.

He enthusiastically promotes the idea of DIY. “I basically offer a workshop environment where the build can be supervised. It’s about skills transferral, really.” One area of tube design that can be troublesome, from the point of view of cost, is transformers. Simply, for the small runs involved, local winders can’t match the prices of even imported units.

Mars’ predictable solution: wind them yourself. Using a transformer winder rescued from a dump – of course – he does limited runs of bespoke units.

“There is stuff lying around that you can pick up for free. Computer bits. Capacitors. Tools. If you want to build some, why not use a hand tool? We have constantly changing technology and the old stuff gets chucked out.”

He holds up the guts of what was deemed to be obsolete medical equipment, pointing out its still usable high-grade capacitors. “And then there is also the issue of the poisonous substances contained in some of this e-waste.”

More to the point, he indicates his Variac, essentially a variable transformer. It still bears the scars of attempts to hack it open on a dump site to get at the copper inside. It still works perfectly.

“We are losing a lot of what makes the world interesting. We are being told that society will just go on forever. I am not a doomsday prophet, but I think it’s worth encouraging and holding on to these skills.”

Geco Audi Velvet
Designer’s view: modified Mauro Penasa circuit, with a sonic signature that’s smooth, almost like a valve amp

Performance: 38-50 W into 8 ohms depending on power supply; 135 W instant peak output power capability; signal to-noise ratio >92 dB

Features: input mute function; output short-circuit protection via internal current limiting circuitry; output over-voltage protection against inductive load transients

Price: about R900, excluding heatsink and transformer

Mars Kit 2
Designer’s view: recently revised to cathode biased EL34 (KT88 or 6550 optional) based Ultra Linear Push-Pull design with a long tail phase splitter and a DC coupled voltage amplifier. Superb at low level, with full bass and clear tops; can go thundering loud with all but very inefficient speakers

Options: 6SL7 as the first triode in the amp; 6N7, 6BX7 and 6BL7s can also be used as phase splitters with the necessary resistor changes

Performance: about 30 watts

Price: R9 900

Let’s get our irons on
So you’re about to enter the great wide world of DIY audio. With the plethora of ideas and schematics out there, you’ll be forgiven for not knowing exactly where to start. Here’s our advice: even if you are adept at wielding a soldering iron, it’s a good idea to start with a kit rather than a design.

What you need to look out for:

* Affordability;
* Thoroughly researched product;
* Backup structure;
* Documentation.

And you’re not on your own. There’s a flourishing DIY community and the success of this year’s Gauteng DIY Showcase has led to proposals for a follow-up event in May 2014.

Also, in a coming issue, we’ll be putting our money where our mouth is by building a kit amp, documenting the process step by step. On completion, it will be up for grabs in a reader competition. Watch this space…

Find out more: and

Video: Karel Mars describes his valve amplifier design
Blog: Casting a vote for DIY
Article: First glass – building a DIY valve amplifier from scratch

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