Electric Guitar Kits Reviews

The MOD 102 electric guitar amplifier is a low-cost ($215) vacuum-tube kit offered by Amplified elements of Tempe, AZ. The kit uses a 12AX7 preamplifier tube, and just one EL84 output tube with solid-state diodes for energy rectification. The amp is rated to produce 5 watts into an 8-ohm load.
SCHEMATIC REVIEW

Referring to the schematic below (mouse click for a bigger pdf variation) we come across an easy to use amp design is employed into the MOD 102, with many elements built to keep the cost only feasible.

Trill Tremolo Schematic (Click to Enlarge)

Starting during the feedback jack we see that the input signal is applied straight to the grid of V1A, the very first 50 % of the 12AX7 preamplifier pipe. This direct-in arrangement sets the “few parts, inexpensive” theme for this amplifier design. The V1A pipe is cathode-biased, and thus, in this instance, a 1.5K ohm resistor is in show with the cathode, evoking the current of this cathode to go up to about +0.9VDC in accordance with ground, with all the grid for that reason at a bad voltage in accordance with the cathode. The bowl of this pipe is tapped with resistor-capacitor network that forms the tone stack (treble & bass) and amount control.

The variable center pin associated with amount potentiometer feeds the grid regarding the second preamplifier stage, V1B. This triode can be cathode biased, plus it’s result feeds the input grid of the production pipe V2. The plate of V2 is fed through main winding associated with the production transformer TR2.

This MOD 102 design is described as “single finished” because it uses one result pipe. This is an excellent setup for a low-power and affordable design, but one ended design is prone to hum in contrast to a push-pull or differential set design where common-mode sound eg hum is terminated.

The origin of hum is typically the heater’s AC voltage, and you will find generally speaking three straight ways to cut back it. The very first is to utilize a center tapped heater winding on the transformer, that is perhaps not applied to the MOD 102, presumably for expense factors.