Power Supply
The EP-PRE is designed to operate from a 9V - 12V DC supply. Maximum allowed
voltage is 12V DC.
The EP-PRE has an internal Charge Pump power supply that boostss 9 V to around
17.3 V, or 12V to 23.3V. If the 12 Volt maximum power supply is exceeded, the
internal voltage may exceed the ratings of the Charge Pump IC. We have designed in
some protection against short term excess voltage, but continued operation from a
supply greater than 12 Volts DC will cause the electronics to fail.
External Power Supply
Power can be supplied from a 9V - 12V DC regulated power pack with a 2.1mm
coaxial plug with negative connected to the centre pin. Although the EP-PRE uses
only about 3mA, the power pack should be rated at greater than 20mA. Use only a
REGULATED supply. The pedal is protected from reverse power connection by a
diode, connected across the positive and negative contacts of the DC jack. If an
incorrectly polarized or AC supply is connected, this diode will effectively short circuit
the supply, protecting the pedal circuitry from damage. If an incorrect power supply
remains connected, the power supply will be damaged.
Battery
We do not recommend powering the EP-PRE from a battery, but a battery
compartment is provided for powering the pedal from a 9V battery.
To access the battery compartment, peel off the non-slip base, which is attached with
genuine Velcro, commercial quality, hook and loop tape. Remove the four screws that
hold the bottom of the box in place.
The battery snap is held to the inside of the box with Velcro. Separate the Velcro and
attach the snap to the battery. The battery will fit between the switch and the end of
the box. The pedal serial number is also located in this area.
Replace the bottom of the box and the non-slip base. Note: The bottom of the box
has foam rubber on the inside, but the rubber does not cover the area where the
battery sits. If the bottom is the wrong way round, it won’t fit over the battery.
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EP-PRE Background
The EP-PRE is a re-creation of the fabled preamplifier section of the Echoplex® EP-
3® Tape Echo. At first glance, the preamp is nothing more than a Common Source
JFET configuration, but when I seriously analyzed the behavior of the circuit, I found
that it has a non-linear phase response. I believe that this phase response is the
secret of the magic tone.
Although the EP-PRE provides a few db of boost when driving a high impedance load,
it was never intended to be used as a boost. A number of guitarists who use the EP-
PRE have called it a “tone polisher”
Using the EP-PRE
Foot Switch
The switch is 3PDT, True Bypass and has gold contacts for reliability.
Note:
The switch can assume a “half-operated” state if the plunger is bumped during
travel and set-up. This is a characteristic of the gold contact switch mechanism and
not a fault. Always fully operate the stomp switch once before using the pedal.
Volume Control
The Volume control is the equivalent of “Echo Volume” in the tape echo unit, wired to
increase the volume as you turn it clockwise, because there is no echo in the EP-PRE.
The level increases for only half of its travel. As you wind it further round, while it
doesn’t change the level, it makes a very subtle difference to the tone.
PCB Jumper
The EP+ uses the new EP circuit board that allows you to
select the tone of either early model EP-3 (S/N 9068 to
9450) or later versions.
When you remove the back cover from the EP-PRE, you
will see the rear of the PCB with the jumper fitted to both
terminal pins. This will give the tone of the early EP-3.
To get the tone of the later EP-3, remove the DC power
plug and/or battery. Gently slide the jumper to the right so
that it slides off both pins. Then slide the jumper back on
to one pin only in order to prevent losing the jumper, in
case you wish to change back to the original EP-3 tone.
Re-connect power or battery, connect your guitar and amp
and try the tone.
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