Two million stomps – will it still work?

The world is full of equipment that are only copies of copies of copies. ABY-switchers are no exception, with most brands simply taking readily available parts and throwing them together to make up their “own” designs and products. 

German engineer Burkhard Lehle deliberately chose a different approach. He analyzed the functionality and problems of practically all available ABY-switchers, and then set about to find alternative routes, in order to get things done better and more efficiently. He also talked to his guitar-playing friends to find out their views on switcher boxes, and what problems guitarists were facing when using them.

The three most common problems with ABY-switchers

Before Lehle revolutionized the market, American ABY-switchers in the Nineties were full of bugs and problems. The three most common complaints were:

  1. The units either had no indicator lights at all or were equipped with underpowered lights, leaving the user literally in the dark as to which amp was selected.
  2. Buzz and hum were prevalent, due to incompetent design and/or badly selected components.
  3. The footswitches were very noisy and fragile.

Of these problems, the last one seemed to be the most irritating and pressing, which is why Lehle chose to solve it first. One of the most idiosyncratic features of a Lehle-switcher is its psychedelic-looking mushroom-shaped footswitch. Lehle has been using this type of switch for over a decade now, and it has always intrigued me.

Joe Bonamassa

Lehle’s big breakthrough came at the beginning of the Noughties, when Joe Bonamassa began using the company’s amp switcher in his set-up. The same switcher box has now been on the young Blues-master’s pedalboard for longer than a decade, and it still works faultlessly! A “vintage” ABY-switcher is an extreme rarity in this field. How is it possible that Lehle’s design has stood up so well to the rigours of continuous touring? Were old Lehles made differently to the current models? 

I have long wanted to take a closer look at a Lehle-switcher from the early 2000s. Finally, I have been given a chance to do so: There’s a pedalboard project coming together on my workbench that includes a ten-year old Lehle 3@1-switcher. 

I find myself wondering whether Lehle has made the same type of compromises in the quality of his products many of his competitors have fallen victim to. Many companies start off with a killer product, which brings them fame and a flood of orders. Then they switch to cheaper production methods, in order to make a larger profit, sacrificing quality in the way. Regardless of my tight schedule at Custom Boards, I pop over to the store and borrow a brand-new Lehle for a comparison between “vintage” and new.

I’m struck by the fact that both units are virtually identical, despite their ten-year age difference. A decade is an eternity, when it comes to component lifetime and production techniques! I give a close look to the psychedelic mushroom-switches on both units, looking at all the small print and the model designations. It’s the same labelling! It must be the same switch!

I turn the Lehle unit in my hands and try to get a glimpse of the inner workings of the switch. How on earth is it possible that this switch can take over ten years of abuse? Just looking at it I can tell that, mechanically, this switch is quite different from your run-of-the-mill stompbox switch. The switch itself isn’t in direct mechanical contact with the mushroom-shaped top, but rather coupled via a spring-loaded mechanism. The mushroom-shaped part of the assembly is attached to the switcher’s casing, keeping the full force of your stomping foot from reaching the circuit board.

Failing switches 

In an interview Mr. Lehle once asked: “What’s the use of an amp switcher that’s unreliable?” Traditional ABY-switchers are equipped with a switch that has a projected lifetime of approximately 10,000 switching actions. These switches are prone to mechanical failure, and they have been designed originally for use with much higher voltages. It only takes a grain of sand or a bit of dust for such a switch to fail or stutter. The result is a lot of noise, most often heard as a loud bang or a scratchy signal.

A discovery at a trade fair

In 1999, Burkhard Lehle came across a strange new type of switch at a Munich trade fair. The switch had a large aluminium pedal part with moving plastic bearings. These bearings were in term connected to a separate switching unit, which was protected by its own housing. This was the way most switches have been working in industrial applications – by indirect coupling. The manufacturer of the switch Lehle saw at that fair promised a minimum lifetime of two million (!) switching actions!

Lehle saw this switch as the solution to his most pressing problem. He started to develop a version of this type of indirect switch for use in his own products. 

A European invasion

The first switchers utilizing this new type of switch were introduced around the turn of the millenium. When they came out in 2001, Lehle’s units were like something from outer space: They revolutionized the concept of what a professional-quality ABY-switcher should be. Lehle left nothing to chance. Each component is the best quality available, and the design of the switcher boxes leaves the signal uncoloured and free from extraneous noise.

Due to their European origins, Lehle’s boxes also looked different. Lehle used German designers to come up with his company’s casings, while his competitors mostly stuck to off-the-shelf effect housings.

But Burkhard Lehle didn’t rest on his laurels, introducing an even smaller switcher model a few years later. The aluminium top still looked like a mushroom, but the actual switch was a different, new design employing a top-of-the-line internal slider switch inside the unit. The newer switch is guaranteed to work one hundred thousand times, and both designs are still used in brand-new Lehles to this day. It sounds kind of macabre, but there is the real possiblility here that a Lehle-switcher will outlive its original owner!

After coming up with a clever solution to the problem with traditional footswitches, Lehle had to tackle the other issues as well.

Getting rid of the hum

If you connect a guitar to more than one amplifier at the same time, the result will invariably be an earth (ground) loop with an ear-splitting amount of audible hum. You get rid of this problem by means of an isolation transformer, which breaks the actual physical contact between the guitar and the amp, while transporting the audio signal onward with the help of electrical induction.

The signal is fed into the so-called primary coil, inducing an electromagnetic current into the shared core of the isolation transformer. As the transformer core is shared by both transformer coils, the electromagnetic current induced by the primary coil causes the secondary coil to produce an alternating current, which is an exact copy of the original signal fed into the primary coil. The signal coming off the secondary coil is then sent to the amplifier.

The straight physical contact between the guitar and the amp is broken, but the audio signal is transported unscathed through the transformer using electromagnetic induction. Breaking the physical, electrical contact between the guitar and the amp also breaks the ground loop. An isolation transformer has an amplification ratio of 1:1, meaning that the transformer is meant to keep the outgoing signal level identical to the incoming signal level. Because a guitar signal is very low-powered, an isolation transformer has to be extremely well made to ensure the signal doesn’t deteriorate. The weaker the signal the more difficult it is to keep it clean and uncoloured. 

Off-the-shelf transformers aren’t good enough

Most bulk-produced transformers have a tendency to shift the signal’s mid-frequency emphasis slightly downward. Because the mid-range is where all the important information is in a guitar signal, this mid-shift sounds like treble attenuation to most of us. A preamplified guitar signal (or using active pickups) will not suffer from this mid-shift phenomenon, but a regular passive electric guitar (especially one with singlecoil pickups) needs a more sensitive, high-quality transformer for effective ground loop defeat without signal deterioration.

How did Lehle solve this issue?

At the beginning of his career, Lehle had to make do with the same off-the-shelf transformers as everybody else. Like the other manufacturers, Lehle, too, had to circumnavigate the known frequency problems. One way is by using a built-in active preamp or buffer amp to pump up the signal level internally, allowing the designer to employ standard audio transformers. The downside to using an internal preamp is that, while such a switcher box successfully does away with hum and phase cancellation problems, it also has an impact on the sound and playing feel. The interaction between guitar and amp is changed, and the signal’s dynamic range is compressed.

Lehle comes up with his own transformer design

Lehle soon got fed up with OEM-transformers, and set about to come up with his own, improved transformer design. He started from scratch and the development took him two years. The result is an isolation transformer that breaks the ground connection, while keeping all of the guitar signal intact. This transformer allows for the natural interplay between a guitar and an amplifier.

Lehle’s legendary LTHZ-transformer makes sure all of the information contained in the guitar signal is kept intact and unchanged. With a singlecoil guitar you will notice this in the brilliant top end and the natural cluck in the attack. Humbuckers won’t mush up, which is especially noticeable on clean settings. You can say without exaggeration that this is the best isolation transformer for guitar use in the world. 

Now he only had to find a (simple) solution to the most annoying practical problem!

A magnifier for the LEDs

It’s a real pain in the proverbial, when you’re having to switch amp configurations mid-gig without any visual clue to what you’re really doing. Did I press the footswitch, or not? The underpowered LEDs on old switchers didn’t really help you that much. Many guitarists complained about this issue, which is why Lehle installed magnifying lenses on top of his indicator LEDs. This made it easy to see your switcher settings, even through the mists of loads of artificial fog from the smoke machine.

Different switching modes are indicated by differently coloured LEDs. This really isn’t rocket science, but many other manufacturers simply didn’t care about the real-world onstage problems gigging guitarists are facing. For Lehle this little improvement was the icing on his cake.

Coming soon: Lehle Components

Burkhard Lehle unveiled his cool plans for the future at 2014’s NAMM Show. He will be releasing his own line of audio components, which will include brand-new designs alongside his older inventions.

Will he manage to come up with other groundbreaking inventions? Will we finally see the demise of the old-style, unreliable footswitch? Can other brands also benefit from Lehle´s indestructible technology? Will reliable Lehle-switches become available to all mankind? 

It’s possible. This man has revolutionized a whole branch of the audio industry, I can’t see why he shouldn’t be able to do it once more!

6.8.2014 Kimmo Aroluoma (translated by: Martin Berka)
The author is one of Custom Sounds’ owners, and an incorrigible guitar and gear enthusiast