ISP Technologies THETA PRE AMP PEDAL User Manual

INTRODUCTION

Congratulations on your purchase of the THETA Preamp Pedal. The THETA Preamp Pedal was
designed to provide the maximum possible over the top performance. With a front end
preamplifier, a full complement of pre and post gain tone, over the top screaming gain, more
than any preamplifier or pedal available plus a full Decimator II G-String noise reduction system.
The THETA Preamp Pedal can be used as a dual channel preamplifier with both a clean preamp
and distortion channel or with the front end preamp overdriving the distortion for massive high
gain. Both Clean and Distort sections provide noise reduction with a full implementation of
Decimator II G-String noise reduction allowing the use of extremely high gain with absolutely no
noise. The THETA Preamp Pedal also incorporates ISP proprietary “dynamic gain modulation”
providing a dynamic feel similar to a tube amplifier with a tube rectifier. Please read this
manual carefully for a through explanation of the THETA Preamp Pedal and its functions.

IMPORTANT SAFTEY INSTRUCTIONS

Please read the following very carefully before operating this unit

 Read ALL instructions carefully before using this unit. Keep these instructions for future reference.

Heed all warnings and follow all instructions.

 Do not use this unit near water, in the rain, or where there is moisture. If this warning is ignored a

serious electrical shock or death may occur.

 Do not attempt to service this unit. No user serviceable parts inside. Refer servicing to qualified,

ISP approved personnel. Servicing is required when the unit is damaged in any way, such as power
adaptor is damaged, liquid has been spilled into the unit, the unit has been exposed to rain or
moisture, does not operate normally, or has been dropped.

 Care should be taken to avoid to spill any foreign objects or liquid into this unit. Avoid exposure of

this equipment to dripping or splashing and ensure that no objects filled with liquid, such as vases,
are placed on the equipment.

 Only use accessories or attachments that are specified by the manufacturer.
 Failure to follow these instructions may void the warranty.

NO UER SERVICABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED ISP

TECHNOLOGIES SERVICE PERSONNELL.

The lightning bolt triangle is used to alert the user to the risk of electric shock.

The exclamation point triangle is used to alert the user to important operating or

maintenance instructions.

POWER REQUIREMENTS

This unit requires the connection of the external AC Power Adaptor to a 120 volt AC outlet.
Do not attempt to connect this unit to any power source other than the specified 120VAC.
The THETA Preamp Pedal will typically draw approximately .5 amps of current.

THETA PREAMP PEDAL CONTROLS

The upper row of controls are for the clean preamplifier. The last control in that row
adjusts the threshold of the Decimator G-String Noise reduction.
The lower row of controls are for the Distortion Circuit. Three footswitches are provided
with the first footswitch allows the player to select Gain1 or Gain2 in the Distortion
section. The second footswitch switches ON and OFF the clean channel preamplifier.
The third footswitch switches ON and OFF the Distortion channel of the THETA pedal.

THETA PREAMP PEDAL REAR PANEL

The rear panel has 4 ¼ inch phone jacks with one for the guitar input, one for the final
output signal and two remote jacks which allow the THETA preamp pedal to be switched
remotely by switch closure (pull to ground) or with relay functions under MIDI control.
The PRE / DIST jack allows remote control switching ON and OFF the Clean Preamp by
swithing to ground the TIP connection of the ¼ inch jack. The Distort section is remotely
controlled by switching to ground the RING connection of the ¼ inch jack. The G1 / G2
jack allows remote control switching between the GAIN1 and GAIN2 front panel control of
the DISTORT section of the THETA pedal. The Power Jack is connected to the supplied
9VAC power adaptor. The THETA pedal internally converts the 9 volt AC signal from the

power adaptor to a professional +/- 15 volt DC power supply. This allows a 30 volt
internal signal swing required for proper headroom and professional level performance.
The THETA pedal will only operate on a 9VAC power source, do not use any other power
adaptor or damage may result.

UNDERSTANDING THE THETA PREAMP PEDAL

BLOCK DIAGRAM

The THETA Preamp Pedal simplified block diagram is shown above. The input is buffered
and connected to the input of the clean PREAMP. The clean preamp includes a shelving
bass and treble control and a mid frequency semi parameteric equalizer which includes a
boost/cut control plus frequency sweep, which will be described in more detail in the
PREAMP section. The output of the EQ section feeds a gain circuit allowing adjustment
of the gain of the clean preamp by up to 50dB. The output of the clean preamp is fed to
the input of the DISTORT circuit. The first section of the Distort circuit is a multi-stage
distortion circuit. The Distort circuit includes dual gain adjustments with Gain1 and
Gain2. The gain section is followed by a bass and treble shelving EQ section which allows
+/- 15db of adjustment. The shelving EQ section is followed by a mid frequency semi
parameteric equalizer which includes a boost/cut control plus frequency sweep. The