MULTIPLE REGULATED VOLTAGES
This is the complete schematic for the circuit that is contained on the AMZ Power Supply PC Board. It features a +9v linear voltage regulator and a voltage converter chip that outputs both +18v and -9v to power PNP pedals that require negative voltage. The basic idea is to create a single pc board that can be used to produce clean, noise-free power for your pedals.
A DC power supply (not included) is required as a voltage source to drive the Power Supply pcb. An 12v transformer is recommended because the input voltage is filtered and available as one of the outputs, but any DC wall adapter with 12v to 18v is suitable.
Multiple filtered and regulated dc voltages are available on the board. IC2 is the 7809 regulator that provides the basic 9 volts output with up to 1A total power consumption. IC1 is a charge pump that doubles the +9v to +18v, though it will always be slightly less on the output because of he voltage drop across the output series diode. The input voltage is filtered and also available for driving pedals and can provide and additional high current output, though it is not regulated.
A DC wall adapter that can provide 12v at 1A is recommended but transformers with current down to 750ma or less can be used as long as the total draw from all of the outputs does not exceed the capacity of the adapter.
This is the blank 2.7" x 1.5" Power pcb. It has an optional LED (with current limiting resistor) on board to indicate when the board is energized.
The 7809 regulated output can easily supply 500 ma or more. The TO-220 regulator is rated for 1A each but I do not recommend drawing that much current from any one of the outputs as excess heat may be produced inside the box.
The voltage from IC2 is processed through a diode and series resistance as a way of imitating voltage sag from a dying battery. It is easy to bypass this feature if not required (see topic below).
How much current does a typical pedal draw? A booster like the LPB-1 or Mini-Booster will need less than 2 ma. and a distortion such as the TS-9, SD-1, Big Muff or Proco Rat will use less than 8 ma. Analog chorus or delays will need less than 20 ma and digital devices use slightly more (45 - 75 ma). Check out the power list for information on the current requirements of many common effects pedals.
The negative 9v converter has less current capacity but can easily drive a PNP booster and fuzz circuit at the same time.
A pedalboard with a booster pedal, two distortions, and 8 more assorted pedals will typically draw less than 500 ma, which is well within the capacity of this design.
The power outputs share a common ground, and though it should work well with the majority of pedals, there are a few designs (mostly digital) that will require a power input with an isolated ground to avoid hum.
The AMZ Power pc board can supply the following:
A single ready-to-solder pc board is $14.00 US plus shipping.Place your order on the AMZ catalog page.
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©2010 Jack Orman
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