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. 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. 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).

Front:

Clean:

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

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

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

4. 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. Middle – Controls the mid range of the tone.
   

2. Bass – Controls the low end/bass of the tonal spectrum.
   

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

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

OverDrive:

1. 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. 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.

Rear:

1. 120VAC power input
   

2. Fuse – 2 amp Slo Blo
   

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

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

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

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

1. OverDrive
   

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

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

1. Speaker output
   

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

Tubes:

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

2. Power – stock tubes are JJ 6L6.
   

Dimensions & Weight:

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

2. Weight - 20 lbs
   

List Price:     $2,399

Hand Built point-to-point all tube guitar amplification

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