Review: Ruppert Basswitch Classic Boost, Clean Boost & Sonic Spark Pedals

October 1, 2014

Luxembourg is a small Western European nation bordered by France, Belgium, and Germany, with the world’s second highest GDP per capita. While interesting in that it is the last remaining grand duchy, (a territory whose head of state is a Grand Duke), it wasn’t until recent years that the land-locked country gave bass players much to think about. But in 2009, Luxembourg-based Ruppert Musical Instruments introduced the Basswitch IQ DI pedal—a serious studio-grade preamp/multitool in pedal form—and the company is now capturing our attention with three new mini-pedals focused on superior audio, smart design, and mechanical integrity.

All Basswitch pedals are built around Lehle True Sound Technology, a process in which the incoming voltage is internally rectified, filtered, stabilized, and regulated to 18 volts. The resulting headroom provides increased clarity and improved peak handling within a wide dynamic range. The high-quality Lehle buffer has an overall conditioning effect on the signal, and sends a clean, low-impedance signal downstream when placed at the front of an effects chain. Top-quality components are used throughout, so the Basswitch pedals are built tough enough to protect their precious innards. The Lehle footswitch mechanically isolates the foot pressure on the actuator button from the internal effect switch, while highly conductive gold-plated relays and switches improve signal transfer and reliability. Basswitch pedals are housed in a pedalboard-friendly steel case with recessed controls to prevent accidental setting changes, or broken pot shafts. All three pedals provide enough gain to drive a power amp, and their high impedance inputs accommodate a variety of pickup types.

The Clean and Classic Boost pedals are three-band EQs with the same controls, and closely related frequency specs, but each with a signature sound that reflects its moniker. The Clean Boost claims the neutrality of a studio preamp, with the bass centered at 40Hz, mids at 640Hz, treble boosting at 5kHz, and cutting at 10kHz. The Classic Boost has more tone coloration, and could be described subjectively as sweeter than its sibling, but other than plus-or-minus a few dB in the mids and highs, the only significant difference is the bass control being centered at 45Hz.

The Sonic Spark shares the same housing as the Boost twins, but is a completely different creature. While equally effective as a preamp, the Spark combines EQ with a harmonic overtone generator to create the fatness of tube response, in varying stages of drive. The ENHANCE knob controls the amount of overtones introduced, ranging from lightly toasted to fully charred, while the INTENSITY dials in the amount of EQ in the signal. The BRIGHT/DEEP control is a powerful, yet simple global EQ.


I tested each pedal as a front end for a Carvin DCM 2000 power amp driving a Greenboy Fearless F112, as well as in-line before a variety of amps. Unfortunately, the trio lacks balanced xlr outputs, but Basswitch tells us it will introduce larger, DI-expanded versions of these pedals at some point. Whenever something is labeled “Classic,” my thoughts immediately go to passive Fender basses. I plugged my ’73 P-Bass strung with 17-year old LaBella Flatwounds into the Classic Boost first, and whether it was the placebo effect or the buffer, the tone seemed smoother even before I activated the switch. Turned on, the Classic added a distinct roundness to the tone, giving the impression of a tube preamp/EQ. The lows were perfectly tuned to fill out the bottom, and avoided severe masking of the mids even when dialed close to maximum. The highs boost at 5kHz, but cut at 10kHz, so even with an extreme roll off, enough mids come through to define the attack. With the bass boosted, and treble down, I was in deep with a thick, punchy tone that would fit right in with ’60s R&B. The mid control worked nicely for bringing out more detail in the fingerstyle tone, but really accentuated pickstyle articulation with warmth, and clarity. Switching over to the Clean Boost with the same settings, I immediately heard the difference. Compared to the Classic, the Clean Boost sounded more open, and the lows seemed wider and less punchy with that particular instrument. It wasn’t bad by any means, but the Classic seemed more in line with the character of the old P-Bass. I switched to a G&L L2500 in active mode and the pedal started making sense. The Clean Boost seemed well-suited to the extended high frequency response of the G&Ls massive MFD humbuckers, and the pedals lower frequency center added depth without mud all the way down to the B string. For one more comparison, I plugged a Carvin Vanquish V49K in passive mode into the Classic Boost and dialed up a nice round fingerstyle tone. The Alnico single-coil pickups sounded right at home in the cozy, tube-like environment, and I easily tailored the effect for a killer slap tone. But when I activated the onboard preamp set flat, the highs of the slap tone felt constrained and a bit harsh. Switching to the Clean Boost, the highs on the V49K seemed to open up, and string popping had a more pleasant tone. The 40Hz-centered bass control brought out a little more thump when I slapped the E string, providing a balanced overall tone.


The Sonic Spark looks simple, but read the manual to get the big picture—the interactive nature of the controls is not immediately intuitive. As directed, I set the Gain level first with the Enhance control in the fully counter-clockwise off position, and the Intensity control maxed. Default position for the Bright/Deep knob is 12:00, but I rolled it down to the bottom right away out of principle. Increasing the Enhance control brings out higher overtones, starting with a gentle buzz at lower settings that becomes a tube-ish break up toward the middle. By the time you’ve maxed the control, it’s pretty thrashy. Caution is advised when mixing high amounts of harmonic material and gain, but ran full-bore with a deep EQ setting, the Sonic Spark turned my ultra-clean reference rig into a snarling beast. The sweep of the bright/deep control made it easy to find the EQ sweet spot, and dialing back on the intensity reintroduced the clean signal for a more balanced effect. With more conservative settings, and a healthy dose of gain, I got a buttery thickness with a slight edge that transformed my humble semi-hollow Eastwood Classic 4 into Jack Casady’s Alembic-modified Guild Starfire. While the Sonic Spark behaved well as a preamp, it excels in a pedalboard as a character-shift or drive. In fact, the pedalboard may be the best place for all the Basswitch babies as the internal components require an external power supply. I put the Sonic Spark in front of an effect chain consisting of: an MXR Bass Compressor, into an EHX POG II, followed by an MXR Analog Chorus, a TC Flashback, and then into a TC Hall Of Fame Reverb—all ran through the effects loop of my Genz Benz Shuttle 9.2. Having swapped the Spark for my usual first effect, a TC Polytune, I heard an instant improvement in the overall signal, even before I turned it on. There was less noise, and my EMG-equipped Lull MV5 had the silky vibe of a studio mix. Sparked up with the Enhance control set low and the EQ toward the deep end, silk turned into burlap, and gave the MV5 a rough-hewn presence. Cranking the overtones in front of the MXR Comp, I got enough sustain and drive to steer the POG II toward Scott Henderson/Gary Willis turf. I’m hooked.

The Clean Boost is a versatile EQ/pre that handles the signal with accuracy, and wide-open dynamics, while its close relative the Classic Boost offers a nostalgic reference back to the days of tube processing. The Sonic Spark is great for general tone fattening, and scary good at summoning up the grunt of a hot, cranky lead-sled.



Classic & Clean Boost $260
Pros Hi-fi quality, well-tuned EQ
Cons None
Bottom Line Great sounding, flexible preamps with a small footprint.

Pros Classic tube fatness in a can
Cons None
Bottom Line A flexible way to add thickness and drive to your sound.


Input Impedance
Output Impedance 150Ω
Frequency Range 30Hz–150kHz (+1/–3dB)
Distortion 0.002%
Signal-to-noise Ratio –96dB @ 1kHz
Max Gain ±15dB
Jacks ¼" in & out
Power 9–15V AC or DC (no adapter included)
Dimensions 5.8" x 2.3" x 1.7"
Weight 0.85 lb
EQ Clean Boost: BASS ±17dB @ 40Hz; MID ±13dB @ 640Hz; TREBLE +13dB @ 5kHz, –13dB @ 10kHz
Classic Boost: BASS +15/–11dB @ 45Hz; MID ±12dB @ 640Hz; TREBLE +10dB @ 5kHz/–12dB @ 10kHz

Input Impedance
Output Impedance 58Ω
Frequency Response 20Hz–75kHz (+0.5/–3dB)
Max Gain +14/-15dB < 1% THD, 1kHz
Jacks ¼" in & out
Power 9–15V AC or DC (no adapter included)
Dimensions 5.8" x 2.3" x 1.7"
Weight 0.85 lb

Made in Germany

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