John Mayer's guitar amp setup.
Notice the Radial JD7 on top.

John Mayer and Keith Urban perform
live on stage at the Grammys.

ELEVATOR DEVELOPMENT

Product designers are very much like musicians. On one hand you have years of training and practice, and on the other a creative spirit that continues to drive your very soul. And much like writing a song, your senses immediately tell you when you have a hit on your hands. The same is true when designing a product. You plug it in and it inspires you to play. The Elevator is one of those products. And as simple as it may seem from the outside, it actually took well over two years to develop and several renditions made before we got it right.

The core of the Elevator is the same 100% class-A circuit that is employed in the Radial JD7 Injector. The JD7 is a multi-output buffer that lets you drive up to 7 guitar amps without messing with your tone. You can be sure that if Carlos Santana, John Mayer, Neil Schon, Steve Lukather, John Petrucci, and Steve Vai use it when they record or play live, rest assured this thing is real.

What makes the JD7 and the Elevator unique is both the circuit design and amazingly quiet performance. Class-A circuit designs are preferred by audiophiles as they do not color the signal like their more efficient class-AB counterparts. The use of discrete parts or individual transistors as opposed to integrated circuits also means that we can apply gain where it is needed and eliminate the use of signal-degrading negative feedback at all stages. This produces a much more natural tone and clarity beyond compare.

Setting the stage for a great booster

Anyone that has played a small vintage amp at 10 knows how wonderful these amps can sound. When you push the limits, the richness of the harmonics sing like angels and the sustain soars like an eagle in flight. The Elevator lets you to drive the input side of the amp into natural saturation without the use of an overdrive or distortion pedal. It is purity at its best. By being able to add extra mid range, sustain is increased and solos stand out without tearing off your ears.

In fact, this design is not new. We first introduced this type of booster when we launched the Radial Switchbone. If you go on line and read the guitar chat rooms and forums, you will find plenty of references where players boast about the Switchbone's amazing tone. The next generation Radial booster was the BigShot PB1. The PB1 has also gained notoriety – primarily by Nashville Pickers – as one of the most amazingly pure boosters ever made. During a discussion with Hellicaster legend Jerry Donahue, Jerry said he loved the PB1 so much, that he never wanted to turn it off. In other words, he wanted to use two of them on his guitar so that he could set a baseline tone with a bit of boost and then elevate the boost again for soloing. This is how the concept of a multi-level booster originated and the Elevator came to be.

Deciding upon the levels

For many guitarists, true-bypass performance is crucial to their tone. True-bypass means that when the guitar pedal is turned off, the signal passes through the pedal without any load or coloration. To take care of the purist, we had no choice but to make this the ground floor.

Although true-bypass circuits are cool, they are not without concerns. With high-gain amps, true bypass circuits are much more susceptible to switching noise. And since they do not buffer or drive the signal in any way, noise from power supplies and other pedals can more easily find its way into the signal path. Level-2 introduces a buffer that lowers the impedance, reduces susceptibility to noise and helps eliminate power-up transients.

As you surely know, many guitarists hate the sound of buffers. There is good reason for this: 99% of all buffers employ integrate circuits that first amplify the signal using hundreds of transistors and then use tons of negative feedback to bring the boost back under control. The Elevator employs individual transistors to minimize the use of negative feedback.

Level-3 lets you adjust the load on the pickup for the most natural tone. During the Radial JD7s development, we came to the realization that loading a pickup with 1 meg-ohms sounds great on a tube amp, but can sound harsh and glassy with a solid state buffer, Drag Control lets you dial in the load to replicate the tone and feel as if connecting directly to your amp. In other words, you get the tone of true-bypass connectivity without the usual problems.

Level-4 lets you then push the 'baseline' boost level so that you can drive the input stage of your amp just a tad harder. This kicks up the distortion and grit and sounds as if you are driving a small amp hard. The 'set and forget' level control is adjusted using a guitar pick.

Once the baseline is set, you can then rise to level 5 by stomping on the power booster and drive the amp even harder. For clean amps, you get more gain and a bit more saturation. For dirty amps, you power-up the front end for more harmonics and sustain. Level -6 opens the door to a 3-position mid-boost switch which lets you increase sustain, just like the old Switchbone!

Integrated circuits versus discrete electronics

The easy way to design a booster is to employ integrated circuits or ICs. The marvelous technical wonders pack hundreds or even millions of transistors into a very small space to generate huge gain. Once the gain has been produced, negative feedback is sent back into the audio stream to control the gain so that the amplifier does not run away. Mix negative gain with a positive signal and something has to give – phase cancellation! This is why most 'purists' hate the sound of solid state amplifiers. The Elevator employs individual transistors for each gain stage so that negative feedback is minimized. The result is a much more natural sounding signal path.

Class-A versus Class-AB amplification

Early amplifiers were class-A, meaning that they employed a single gain producing devices such as a tube or transistor to amplify the full audio wave. The problem with class-A circuits is that they never shut off and are not very efficient. Class-AB amplifiers were developed to solve these problems by breaking the wave into two parts – positive and negative (push – pull) where each half of the wave is amplified individually. After the signal is amplified, the two half waves are brought back together to produce the final output. The problem of course is bringing the two half waves back together in perfect alignment. As this is practically impossible, zero-cross distortion in introduced causing the harshness that folks do not enjoy.

Integrated Circuits
Integrated circuits contain hundreds of transistors in a super compact package.
Discrete Components
Individual transistors allow precise control of the gain at every stage.
Negative Feedback
The signal is first amplified and a portion is sent back as negative feedback (R2). Less negative feedback sounds better.
Class-A Buffer
The simplicity of a class-A circuit with a single-ended design is free from zero-cross distortion.
Class-AB Buffer
Class-AB circuits break the wave in two components and then bring them back together.