NAMM 2014: Colby Amplification Introduces the Mod Machine

January 21st, 2014

On the heels of Colby Amplification’s award-winning debut amp, the dual tone booster, the company has introduced the Mod Machine, a powerful amplification tool for recording, club gigs, practice and touring. The Mod Machine is an all-tube, hand-wired, British-style amplifier capable of multiple sounds and power amp configurations.

Starting from a full, clean sounding “JTM” circuit, the MOD MACHINE can morph to everything from a “Plexi” to a metal panel “Master Volume” to searing higher-gain sounds.

The power section includes four different modes (Pentode/Triode/Cathode/Fixed) for additional tonal options with corresponding power ratings from 12 to 50 watts or 22 to 100 watts, depending on the model. The all-tube FX loop has send and return level controls so you can connect time-based pedal and rack effects for maximum tone and flexibility.

The comprehensive MASTER section includes Pre and Post Master Volume controls as well as Presence and Hi Trim controls so you can dial in the right settings for low- and high-gains sounds and achieve the sound you are looking for at any volume level.

Other significant controls are the four-way pre-emphasis, three-way Shift switch and a switchable extra gain stage (STAGE 2). STAGE 2 also reconfigures the preamp for a tonal shift to a more modern sound and has its own Gain control which in conjunction with the Emphasis and Shift switches plus dual master volumes allows the user to dial in just about everything from clean to mean to scream.


Power: 12/22/36/50 watts (with two EL34s), 22/40/68/100 watts (with four EL34s)
Tubes: two or four EL34s, four 12AX7s
Front panel controls and switches: Volume, Treble, Mid, Bass, Stage 2 Volume, Pre Master Volume, Presence, Hi Trim, Post Master Volume, On/Off, Standby, Four-way pre Emphasis, Three-way mid Shift, Stage 2 On/Off, FX loop On/off
Back panel controls and switches: Mains and B+ fuses, Fixed/Cathode bias switch, Pentode/Triode switch, Main and Extension speaker outputs, Impedance Selector (4, 8 & 16), Send and Return Jacks, Send and Return level controls
Dimensions: (W) 24”, (H) 10”, (D) 9.5”
Weight: 35/37 lbs.

For more about Colby Amplification, visit

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  1. Posted by Andrea on October 17th, 2015, 11:39 [Reply]

    Single-ended audio output trafenormsrs are specially designed with a small gap in the iron core material to prevent the DC plate current from saturating the core with magnetic flux. Power trafenormsrs do not have this gap (they would burn up if they did).Push-pull audio output trafenormsrs do not have the gap, because the flux due to the DC current flows in opposite directions toward both plates, thus cancelling out their respective fluxes in the core.It is technically possible to use a power transformer as a push-pull output transformer and your calculations are basically correct for impedance, voltage, etc. The HV output windings of most power trafenormsrs are usually split so, you could use the HV windings for the plates and the filament windings for the speaker. But, again, it cannot be used in a single-ended application.Furthermore, power trafenormsrs are designed for efficient power transfer at 50/60 Hz without regard to frequency response. Audio trafenormsrs are designed specifically for a wide (audio) bandwidth. You might get good bass with a power transformer as an output transformer, but that’s about it.Bottom line: you really need a single-ended audio output transformer designed for the tube you plan on using and the power level you plan on producing..


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