Nine Series Effects Pedals

maxon nine series guitar effects pedalsSince their introduction in the early 1980s, Maxon Nine Series designs have achieved a legendary status with pedal connoisseurs around the globe. The reasons for this are simple - superior sound quality and innovative features that offer a seamless interface between performer and performance. 20 years later this rule still holds true. Now available with improved circuitry including JRC4558 IC chips and True Bypass Switching, Maxon Nine Series effects remain the standard by which all others are judged.

TBO-9 True Tube Booster/Overdrive


More Info

The TBO-9 combines Clean Boost and Overdrive capabilities with a tube gain stage to create a versatile tone-shaping tool.

The ideal complement to non-master volume tube amps, the TBO allows you to drive a clean or semi-clean amp to the breaking point, giving it that “on 10” tonality at a much lower volume level and without altering the amp’s signature tone.

The TBO-9’s tube stage is controlled by the Boost knob which adds a fat, warm bottom end with a slight mid bump as it increases the output level.

The Drive knob blends clean and distorted signals, allowing the user to dial in a small amount of grit with minimal coloration.

The TBO-9 features internal voltage doublers that bump the incoming 9 VDC up to 30 VDC for massive headroom and maximum transparency.  

When you need to drive your amp without driving the audience towards the door, the TBO-9 does the job without commanding the center stage.

Why Choose Maxon?

The TBO-9 is the perfect complement to non-master volume tube amps, boosting level and drive while retaining maximum transparency.

Tech Talk

The basic TBO-9 circuit architecture is very similar to the Maxon OD820, including the dual-function Drive pot that blends clean and dirty signals while increasing saturation.

The circuit starts with a tube gain stage featuring a mil-spec 5703WB JAN Raytheon sub-miniature vacuum tube positioned at the front of the audio path.  This tube stage does not provide any distortion, with the exception of overdriving the input of the clipping op amp.

After the tube gain stage, the TBO’s secondary gain section features a dual-stage clipping design that combines the classic “808” clipping (diodes in feedback loop) with a pair of diodes to ground ala’ the SD-9 and RAT.  This design effectively clips the signal twice, and the round smooth clipping of the feedback loop followed by the edgier diodes to ground adds a slight “chewiness” to the pedal’s overdrive voice.

The TBO-9 features internal voltage doublers that bump the incoming 9 VDC up to 30 VDC for stable tone with massive headroom and zero harmonic distortion.

The TBO also features Maxon’s In-Rush Current Control system - As soon as power is applied to the pedal, a small current is applied to the tube and begins heating it at a very low voltage (much like a tube amp standby switch) - This system dramatically extends the tube life.

The TBO-9 features Mechanical True Bypass switching via a Fujisoku 4PDT switch.

NOTE ON POWERING THE TBO-9 - this pedal’s voltage regulator IC requires a high inrush current of approximately 2000 mA upon startup.  When using with a Power Brick such as the Voodoo Labs Pedal Power 2+, this pedal should be connected to a high current power jack when possible.

Mods & Mends

Dedicated Clean Knob Mod

Increased Drive Mod


tbo-9 video 01


The Best Tube Boost/Overdrive Pedal
tbo-9 video 02


Tone Talk - Episode 4
tbo-9 video 03


TBO-9 True Tube Booster Overdrive Guitar Pedal
tbo-9 video 04

Pro Guitar Shop Demos

TB0-9 True Tube Boost Overdrive Demo



Input Impedance: 500K Ohms Output Impedance: 10K Ohms or less Maximum Gain: 52 dB (1.6 KHz) Equivalent Input Noise: -110 dB or less (IHF-A) Control: BOOST, DRIVE, TONE, LEVEL Switch: BYPASS/EFFECT (mechanical TBS) In/Out: INPUT, OUTPUT, INVERSE OUTPUT Indicator: BYPASS/EFFECT LED Internal Circuit Voltage: 30 VDC (DC-DC Converter) Current Consumption: 270 mA / 9 VDC Dimensions: 74 mm (W) x 124 mm (D) x 54 mm (H) / 2.9” (W) x 4.9” (D) x 2.13” (H) Weight: 560 g (excluding AC adaptor) / 19.75 Oz. Power Supply: Maxon AC2009 (no battery operation) Accessory: Maxon AC2009 Option: Adaptor type (for foreign countries) * All specifications are subject to change for improvement without notice or obligation. All brand names and product names are trademarks or registered trademarks of their respective companies.
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  • Clean Booster/Overdrive pedal with Tube gain stage
  • Employs mil-spec sub-miniature vacuum tube
  • Great as a tube amp booster to add warmth
  • Boost knob controls level of tube gain
  • Dual-purpose Drive control with clean blend function
  • Internal voltage regulator runs 30 Volts to tube
  • Heater In-rush current control warms tube upon power-up
  • True Bypass Switching


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TBO-9 True Tube Booster/Overdrive
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