The JoMama OverDrive is an all tube amplifier designed for the guitarist who wants a taste of a “D” style single channel amp with foot-switchable overdrive boost. The “spanky” clean preamp has a very percussive nature that is extremely inspirational. The JoMama OverDrive has (3) front panel mini toggle switches that include: a bright switch; a 3-position mid-boost; and an OverDrive boost. The Mid Boost switch selects between 3 different treble control voicings that range from sparkling - to - thick & creamy. This amplifier also has the ability to accept a wide variety of octal power amp tubes (we usually ship them with 6L6’s, but 6V6’s & EL34’s are also popular choices).

  1. Bullet Clean – This preamp stays nice and clean and allows you to crank the power amp to achieve a highly percussive tone that taps into the compression and sustain of the power amp tubes.

  1. Bullet OverDrive – Activating the OverDrive circuit adds two additional gain stages that are tuned/tweaked individually for each amplifier. The result is an overdrive that ranges from clean & harmonically rich to smooth & thick with saturation. Again the OverDrive section of this amplifier is voiced to sweetly drive the Power tube section into a wonderful touch sensitive tone. There are (3) additional controls activated when the OverDrive is engaged: Gain & Level (front panel); and Trim (rear panel).

JoMama  OverDrive



  1. Bullet Volume – Controls the clean preamp volume and sets the initial gain structure for the OverDrive.

  2. Bullet Bright Switch – Mini toggle switch adds high end sparkle.

  3. Bullet Treble – Controls treble & the bite of the tone. The voicing is modified with the following mid boost switch.

  4. Bullet Mid Boost Switch – 3-position Mini toggle switch expands the treble controls voicing as follows:                                                                                          

                                      Upper position - thickest and creamiest tone

                                      Center position - tight/bright tone

                                      Lower position - thicker tone with added high mids

  1. Bullet MiddleControls the mid range of the tone.

  2. Bullet BassControls the low end/bass of the tonal spectrum.

  3. Bullet Accent – Adds high end brilliance/presence to the final preamplifier tone.

  4. Bullet Master – Controls the overall volume of the preamplifier before entering the power tube stage.


  1. Bullet Gain – Controls the drive/output of the first added gain stage that in-turn feeds the input of the 2nd overdrive gain stage: lower settings add harmonic content to the clean tone: higher settings add saturated overdrive.

  2. Bullet Level – Controls the output of the 2nd added gain stage & the overall volume of the total overdrive stages. Balances the overdrive volume with the clean volume.


  1. Bullet 120VAC power input

  2. Bullet Fuse – 2 amp Slo Blo

  3. Bullet Bias Trim – 20 turn fine bias adjustment for the power tubes

  4. Bullet Bias CHK Left  – Positive test jack for left power tube bias measurement

  5. Bullet Bias CHK Ground – Negative/ground test jack for bias adjustment

  6. Bullet Bias CHK Right  – Positive test jack for right power tube bias measurement

  1. Bullet OverDrive

  2. Bullet Pedal  - Foot-switch cable input - Note: When the foot-switch cable is inserted into this jack, the front panel channel switch is bypassed.

  3. Bullet Trim  - Controls the amount of signal from the clean preamp that drives/feeds the OverDrive stages.

  1. Bullet Speaker output

  2. Bullet Impedance switch – select 2, 4, 8, & 16 ohms


  1. Bullet Preamp - (3) 12AX7 – premium selected from Ruby Tubes, Tube Amp Doctor, GrooveTubes,  JJ, Sovtek, and Electro Harmonix, depending on availability & sonic qualities.

  2. Bullet Power – stock tubes are JJ 6L6.

Dimensions & Weight:

  1. Bullet Dimensions - 17.5" width, 9.0" height, 9.5" deep

  2. Bullet Weight - 20 lbs

List Price:     $2,399


Hand Built point-to-point all tube guitar amplification

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