|Burhard G Lehle, the man behind the switchers|
The brightly colored boxes with the mushroom- shaped footswitches popped onto the scene a while back, offering up Teutonic quality and innovation along with a difficult to pronounce name. Having scored U.S. distribution last year with Dana B. Goods, Lehle-branded boxes (pronounced lee-la) have found their way onto quite a few pedalboards stateside in a short amount of time, many of which belong to artists notorious for their search for the ultimate tone. Figuring these guitarists were onto something, our own intrepid Dirk Wacker tracked down Burkhard G. Lehle to ask, “Dude, what’s up with those switches?”
It all started one day when a customer came into my shop and asked for a special switching solution. I’m always open-minded to new things, so I started to investigate and I soon realized that there were no practical solutions. Due to the void in the market, I built two prototypes and showed them to some exhibitors at the Musikmesse in Frankfurt, Germany. When I returned home, I had several orders for my switcher. My first prototypes were built into the standard Hammond die cast cases, using standard mechanical switches. As demand increased, I developed my first generation of switchers in 2001. These switchers had the bigger, mushroom-shaped knobs and the indestructible switching matrix. These raised a lot of international interest; that’s how it all started.
The special thing about my switchers is the design and the exclusive use of relays and switches with gold-plated contacts. My pride and joy is the Hi-Z transformer that I developed, which is used in the Dual SGoS, Little Dual and the P-Split. I really believe that it’s important to keep the individual interaction of the guitar, amp, playing style and the cable alive, even when you need to switch. The signal that comes out of a typical guitar or bass is so weak that a crappy cable or cheap contact materials can noticeably ruin your tone. To switch such weak signals without any tone loss, you need very special contact materials and a special design. Nothing beats gold-plated contacts for switches and relays. This is the only guaranteed way for switching weak signals without any degeneration.
In general, my switchers are passive, without any semiconductors in the signal path. The sound of a guitar and bass is created by the interaction between the weak instrument signal and the amp’s sensitive input stage. With an active buffer, you can dramatically change the sound and feel of a guitar. Buffers and other active elements can be very useful and sound good, but in my opinion, they should not be involved in any switching process.
Could you tell us more about the transformer?
I developed the LTHZ transformer because when you are routing a guitar signal to two amps, you will typically have two problems: ground loops, which are especially annoying when using overdrive; and phase inversion, possibly causing a thinner sound. Both problems can be cured by using a transformer. Standard transformers are not built for guitar signals; even the most expensive models will change your tone noticeably. A guitar pickup isn’t like a mic, with even bass, mids and highs. The typical electric guitar sound is the product of the resonant frequency in the mids of the pups in combination with the guitar’s electronics, your cable and the input stage of the amp. When you use a standard transformer together with a guitar signal, you will shift this mid peak towards the lower frequencies, resulting in a completely different sound, often perceived as a loss in high frequencies. Strong signal sources like active outputs from a keyboard don’t have any characteristic peaks and a standard transformer will not change the sound noticeably. A guitar signal is a much weaker signal, comparatively, while its input impedance is much higher than any line-level input.
You can use this effect to build a low-cost, A/B/Y box. You only have to boost the signal with a small active preamp, then you can use any standard transformer afterwards. This will get rid of the phase and ground problems we talked about, but this way will also destroy the interaction between the guitar and the amp. The best thing to do is to use a transformer that keeps this interaction untouched – that does not change the resonant peaks of the pickup in combination with the amp. Because there was no manufacturer producing such a transformer, I developed my own, starting from scratch. This transformer, used inside the Dual SGoS, Little Dual and the P-Split II, has a very high impedance and leaves the guitar signal untouched. The typical input impedance of a guitar amp is around 1 Megohm. The native impedance of my transformer at 1kHz is approximately ten times higher. Because of this, the transformer will not influence the mid frequencies in any way. At the same time, the coil’s DC resistance is very low while the coil inductance is very high. Because of this, the signal will not lose any volume. Coupled with a low-impedance source like a mixing console or a preamp output, it is possible to stay absolutely linear between 20Hz and 100kHz. I also sell my LTHZ transformer to audio and hi-fi manufacturers.
Can you tell us a little bit about your new generation products?
I worked two years on the new generation of my switchers. My main goal for developing these new switchers is easy; I wanted to develop the best switchers ever. The new design of the switchers was developed by two young and very talented industrial designers, Busse and Medugorac. I designed the first generation, but my main work is engineering, so I decided to let these two guys do the design work for the new generation of switchers. I think this was a good decision because I’m pretty sure we will hear their names again in the future – they did a really fantastic job.