INTRODUCTION
Congratulations on your purchase of the THETA Head. You are now the owner of the
most innovative guitar amplifier ever produced. The THETA Head was designed to
provide the maximum possible over the top performance. With dual front end
preamplifiers, a full complement of pre and post gain tone, over the top screaming gain
(more than any amplifier available) in the distortion channel, dual Decimator noise
reduction systems, studio quality digital reverberation, 300 watts of built in power and
the 6 button THETA Foot controller the THETA Head defines a new standard in guitar
amplification. The THETA Head has dual processing channels, Clean and Distort, both
incorporating independent Decimator noise reduction systems allowing the use of
extreme gain with absolutely no noise. The THETA Head also incorporates ISP
proprietary “dynamic gain modulation” providing “the feel” answering the quest of the
professional guitar player.
Please read this manual carefully for a through explanation of the THETA Head and its
functions.
PRECAUTIONS
NOTE: IT IS VERY IMPORTANT THAT YOU READ THIS SECTION TO PROVIDE YEARS OF
TROUBLE FREE USE. THIS UNIT REQUIRES CAREFUL HANDELING.
All warnings on this equipment and in the operation instructions should be adhered to and all
operating instructions should be followed.
Do not use this equipment near water. Care should be taken so that objects do not fall onto
and liquids are not spilled into the unit through any openings.
The power cord should be unplugged from the outlet when the unit is left unused for a long
period of time.
DO NOT ATTEMPT TO SERVICE THIS EQUIPMENT. THIS EQUIPMENT SHOULD BE
SERVICED BY QUALIFIED SERVICE PERSONNELL ONLY. DO NOT MAKE ANY INTERNAL
ADJUSTMENTS OR ADDITIONS TO THIS EQUIPMENT AT ANY TIME. DO NOT TAMPER WITH
INTERNAL ELECTRONIC COMPONENTS AT ANY TIME. FAILURE TO FOLLOW THESE
INSTRUCTIONS WILL VOID THE WARRANTY OF THIS EQUIPMENT, AND MAY CAUSE A
SHOCK HAZZARD.
POWER REQUIREMENTS
This unit requires connection to a 120-volt AC outlet. Do not cut or disconnect the ground
pin on the power cord. Do not attempt to connect this unit to any power source other than
the specified 120VAC. The THETA Head will typically draw approximately four amps of
current when driving a 4-ohm load.
Understanding the THETA amplifier
6. POWER SWITCH
Switches the unit on and off.
7. POWER LED
FRONT PANEL
THETA PREAMP1
1. PREAMP1 ON LED
This led indicates when PREAMP1 is active and in the signal path. NOTE: The
PREAMP1 switch on the THETA FOOTCONTROLLER switches PREAMP1 on and off.
PREAMP1 is functional only when the CLEAN channel is selected. PREAMP1 and
PREAMP2 will automatically switch with the channel selected.
2. PREAMP1 GAIN CONTROL
This control adjusts the amount of gain in the signal path of PREAMP1.
3. BASS
This control adjusts the amount of boost or cut in the low frequency portion of the
spectrum of PREAMP1. The available BASS boost and cut range is +/-15 decibels.
4. MIDRANGE BOOST/CUT CONTROL
This control works in conjunction with the SWEEP frequency control 5. The MID and
SWEEP controls work together to provide a semi-parametric tone control. When the
MID control is set at 12:00 straight up there is no boost or cut in the MID frequency
portion of the spectrum. The graph below shows the response of the MID boost/cut
and SWEEP controls. The MID control allows +/- 12db of boost or cut to be applied
at the frequency determined by the SWEEP control.
5. SWEEP FREQUENCY CONTROL
This control works in conjunction with the MID boost/cut control and adjusts the
center frequency of the MID boost or cut signal. At the full counter clockwise setting
the midrange frequency will be at 300Hz, at the full clockwise setting the center
frequency of the midrange will be at 6KHz. NOTE: when the MID control is set at
12:00 straight up the SWEEP will not have any affect on the signal since there is not
boost or cut being applied.
6. TREBLE CONTROL
The TREBLE control adjusts the boost or cut that is applied in the high frequency
portion of the spectrum of PREAMP1. The available TREBLE boost and cut range is
+/-15 decibels.
THETA PREAMP2
1. PREAMP2 ON LED
This led indicates when PREAMP2 is active and in the signal path. NOTE: The
PREAMP2 switch on the THETA FOOTCONTROLLER switches PREAMP2 on and off.
PREAMP2 is functional (active) only when the DISTORT channel is selected.
PREAMP2 and PREAMP1 will automatically switch with the Distort or Clean channel is
selected.
NOTE: ALL OF THE REMAINING FUNCTIONS OF PREAMP2 ARE IDENTICAL
TO PREAMP1 AND WILL NOT BE REPEATED.
THETA CLEAN CHANNEL
1. CLEAN CHANNEL ON LED
This led indicates when the CLEAN CHANNEL is active. NOTE: The CHANNEL
SELECT switch on the THETA FOOTCONTROLLER switches between the CLEAN
CHANNEL and DISTORT CHANNEL. THE CLEAN can be selected by using either the
THETA FOOTCONTROLLER CHANNEL SELECT switch or by pushing the CHANNEL
SELECT switch on the from panel of the THETA amplifier.
2. PRESENCE CONTROL
This control adjusts the amount of high frequency presence in the CLEAN channel.
The corner frequency of the PRESENCE control is set at 15Khz with a maximum if
15db of boost.
3. BASS
This control adjusts the amount of boost or cut in the low frequency portion of the
spectrum of PREAMP1. The available BASS boost and cut range is +/-15 decibels.
4. MIDRANGE BOOST/CUT CONTROL
This control works in conjunction with the SWEEP frequency control 5. The MID and
SWEEP controls work together to provide a semi-parametric tone control. When the
MID control is set at 12:00 straight up there is no boost or cut in the MID frequency
portion of the spectrum. The graph below shows the response of the MID boost/cut
and SWEEP controls. The MID control allows +/- 12db of boost or cut to be applied
at the frequency determined by the SWEEP control.
5. SWEEP FREQUENCY CONTROL
This control works in conjunction with the MID boost/cut control and adjusts the
center frequency of the MID boost or cut signal. At the full counter clockwise setting
the midrange frequency will be at 300Hz, at the full clockwise setting the center
frequency of the midrange will be at 6KHz. NOTE: when the MID control is set at
12:00 straight up the SWEEP will not have any affect on the signal since there is not
boost or cut being applied.
6. TREBLE CONTROL
The TREBLE control adjusts the boost or cut that is applied in the high frequency
portion of the spectrum of CLEAN CHANNEL. The maximum TREBLE boost and cut
range is +/-15 decibels.
7. REVERB LEVEL CONTROL
The REVERB control adjusts the amount of digital reverb that is added when using the
CLEAN channel. The digital REVERB in the THETA amplifier has a bandwidth of 18KHz
and also includes a digital implementation of the Decimator noise reduction to ensure
that the digital reverb has a dynamic range greater than 110db.
8. DECIMATOR NOISE REDUCTION
The CLEAN channel DECIMATOR control adjusts the threshold of the CLEAN channel
noise reduction. The DECIMATOR noise reduction is a down low-level downward
expander incorporating ISP‟s patent pending TIME VECTOR PROCESSING.
A BRIEF EXPLANATION OF THE DECIMATOR NOISE REDUCTION SYSTEM
Low Level Downward Expansion is performed by use of a high quality voltage
controlled amplifier controlled by an RMS based audio level detection circuit. A Time
Vector Processing circuit is used which varies the release response over a 1000 to 1
ratio and controls the release response of the Downward Expander. The release
response will be extremely fast, on the order of 2 milliseconds, if the input signal has
a fast decaying envelope and upwards of 2 seconds if the input signal has a slow
decaying signal. Downward Expansion takes place when the input signal level drops
below the preset threshold. For example: if the threshold is set for 0db and input
signal of 0db with produce no expansion. As the input signal drops below 0db,
downward expansion starts and increases exponentially the farther the input signal
drops below the threshold point. The figure below shows the response of the
Expander with a 0db threshold.
9. LEVEL CONTROL
The LEVEL control adjusts the output LEVEL of the CLEAN channel. NOTE: The final
output level is determined by the setting of the MASTER LEVEL CONTROL.
THETA DISTORT CHANNEL
1. CHANNEL SELECT SWITCH
The CHANNEL SELECT switch changes the THETA operating channel from CLEAN to
DISTORT. The CHANNEL SELECT switch is a momentary switch that changes the
channel upon pushing the switch. This switch can be used with or without the THETA
FOOTCONTROLLER connected.
2. DISTORT CHANNEL ON LED
This led indicates when the DISTORT CHANNEL is active. NOTE: The CHANNEL
SELECT switch on the THETA FOOTCONTROLLER switches between the DISTORT
CHANNEL and CLEAN CHANNEL. THE DISTORT CHANNEL can be selected by using
either the THETA FOOTCONTROLLER CHANNEL SELECT switch or by pushing the
CHANNEL SELECT switch on the from panel of the THETA amplifier.
3. GAIN CONTROL
This control adjusts the amount of gain in the DISTORT CHANNEL. The maximum
amount of gain will be determined by the setting of the DISTORT CHANNEL GAIN and
PREAMP2 gain only if PREAMP2 is switched on. The maximum amount of available
gain is greater than 140db if PREAMP2 is switched on.
4. BASS CONTROL
This control adjusts the amount of boost or cut in the low frequency portion of the
spectrum of the DISTORTION circuit. The available BASS boost and cut range is +/15 decibels.
5. MIDRANGE BOOST/CUT CONTROL
This control works in conjunction with the SWEEP frequency control 5. The MID and
SWEEP controls work together to provide a semi-parametric tone control. When the
MID control is set at 12:00 straight up there is no boost or cut in the MID frequency
portion of the spectrum. See the graph shown in the CLEAN CHANNEL section, which
shows the response of the MID boost/cut and SWEEP controls. The MID control
allows +/- 12db of boost or cut to be applied at the frequency determined by the
SWEEP control.
6. SWEEP FREQUENCY CONTROL
This control works in conjunction with the MID boost/cut control and adjusts the
center frequency of the MID boost or cut signal. At the full counter clockwise setting
the midrange frequency will be at 300Hz, at the full clockwise setting the center
frequency of the midrange will be at 6KHz. NOTE: when the MID control is set at
12:00 straight up the SWEEP will not have any affect on the signal since there is not
boost or cut being applied.
7. TREBLE CONTROL
The TREBLE control adjusts the boost or cut that is applied in the high frequency
portion of the spectrum of DISTORTION CHANNEL. The maximum TREBLE boost and
cut range is +/-15 decibels.
8. REVERB LEVEL CONTROL
The REVERB control adjusts the amount of digital reverb that is added when using the
DISTORTION channel. The digital REVERB in the THETA amplifier has a bandwidth of
18KHz and also includes a digital implementation of the Decimator noise reduction to
ensure that the digital reverb has a dynamic range greater than 110db.
9. DECIMATOR NOISE REDUCTION
The DISTORTION channel DECIMATOR control adjusts the threshold of the CLEAN
channel noise reduction. The DECIMATOR noise reduction is a down low-level
downward expander incorporating ISP‟s patent pending TIME VECTOR PROCESSING.
Setting the Decimator Noise Reduction System:
Setting the Decimator Threshold for proper use with the Distortion channel is easy if
you follow these instructions. Set the Decimator Threshold full counterclockwise.
Adjust the Distortion gain and Preamp2 gain as desired for your playing. Slowly
increase the Decimator Threshold until the background noise just disappears. This
will be the best possible setting for the Decimator. Increasing the Threshold beyond
this point will cause expansion to be more aggressive than desirable. Some
experimentation may be required to get the best possible Threshold setting.
10. LEVEL CONTROL
The LEVEL control adjusts the output level of the DISTORTION channel. NOTE: The
final output level is determined by the setting of the DISTORTION LEVEL and the
MASTER LEVEL CONTROL.
THETA MASTER CONTROLS
1. DECIMATOR IN/OUT SWITCH
This master DECIMATOR IN / OUT switch activates both the CLEAN channel and
DISTORTION channel DECIMATOR noise reduction systems.
2. EFFECTS LEVEL CONTORL
This control adjusts the level of an externally connected effects processor. NOTE: The
loop must be turned on via the THETA FOOTCONTROLLER in order for the EFFECTS
level to operate.
3. SOLO LEVEL
This control adjusts the amount of boost that will be applied to the output signal
when the THETA FOOTCONTROLLER boost switch is activated. This control allows
the user to switch on and off via the THETA FOOTCONTROLLER up to 6db of output
level boost if desired for soloing.
4. LEVEL / MASTER OUTPUT LEVEL
This control determines the master output LEVEL of the THETA guitar amplifier.
THETA REAR PANEL
1. AC POWER RECEPTICAL / FUSE
The AC power cord connects to this receptacle. The AC receptacle also houses the
power line fuse. Replace the fuse only with the same size and type as used originally
installed in the THETA guitar amplifier.
2. SPEAKER OUTPUT JACK
This ¼ PHONE jack provides the output signal for connection to an external speaker.
The minimum load impedance should be 4 ohms total between output 2 and 3.
3. SPEAKER OUTPUT JACK
This ¼ PHONE jack provides the output signal for connection to an external speaker.
The minimum load impedance should be 4 ohms total between output 2 and 3.
4. SEND OUTPUT JACK
The SEND output jack is used to connect an external signal processor/effects unit.
Connect the SEND output to the input of the external effects processor.
5. RETURN INPUT JACK
The RETURN input jack is used to connect to the output of an external effects
processor. The external effects processor connected to the THETA is switched in and
out via the THETA FOOTCONTROLLER.
6. FOOTSWITCH CONNECTOR
This connector is used to connect the THETA FOOTCONTROLLER. The THETA
FOOTCONTROLLER is connected using the 15-pin Dsub cable supplied with the
THETA.
7. DIRECT OUT
The DIRECT OUT provides a speaker simulated recording output for direct connection
to a mixing console.
THETA FOOTCONTROLLER
1. PREAMP1 SWITCH
This switch turns on and off PREAMP1 the CLEAN channel preamp on the THETA.
2. PREAMP1 LED
When this LED in on PREAMP1 is active, switched on.
3. PREAMP2 SWITCH
This switch turns on and off PREAMP2 the DISTORTION channel preamp.
4. PREAMP2 LED
When this LED in on PREAMP2 is active, switched on.
5. CHANNEL SELECT SWITCH
This switch changes the channel selected between CLEAN and DISTORT.
6. CLEAN CHANNEL LED (RED)
This red LED indicates when the CLEAN CHANNEL is on and active.
7. DISTORT CHANNEL LED (BLUE)
This Blue LED indicates when the DISTORTION CHANNEL is on and active.
8. REVERB SWITCH
This switch turns on and off the THETA„s internal digital reverb. NOTE: The digital
reverb will only function when the THETA FOOTCONTROLLER is connected and the
reverb circuit is switched on.
9. FX LOOP
This switch turns on and off the external effects loop allowing use of an external
effects processor. NOTE: The FX LOOP will only function when the THETA
FOOTCONTROLLER is connected and the FX LOOP is switched on.
10. BOOST
This switch turns on and off the THETA BOOST function allowing up to 6db of boost
of the output level of the amplifier.
11. D-SUB CONNECTOR
Connect the 15-pin D-SUB connector between this connector and the D-SUB
connector on the back of the THETA amplifier.
FUSE REPLACEMENT
1. Use a small screwdriver as shown to slide the fuse
cover out from the power inlet module. The fuse
can be found inside the fuse cover module after it
is pulled out.
NOTE: A SMALL COMPARTMENT IS ALSO PROVIDED
WITHIN THE FUSE COVER MODULE FOR
STORING A SPARE FUSE.
2. After replacing the fuse with another of identical
specifications, push the fuse cover module fully
back into place, ensuring that the fuse has snapped
onto the fuse holder inside the power inlet module.
Input Impedance
Maximum Gain in Distortion channel
Treble Control /Preamp 1 and 2
Treble Control /Clean and Distort
Bass Control /Preamp 1 and 2
Bass Control /Clean and Distort
Mid Sweep Frequency /Preamps
Mid Sweep Frequency /Channels
Mid Boost/Cut Range /Preamps
Mid Boost/Cut Range /Channels
Presence Range (Clean Channel)
Decimator Effective Noise Reduction
Digital Reverb bandwidth
D-CAT amplifier output power
D-CAT amplifier protection
Boost Level
Direct recording output level
THETA footswitch cable
THETA power consumption
Fuse Slo Blo
Dimensions
Weight
500k ohms
Greater than 140db
+/-15db at 10Khz
+/-15db at 10Khz
+/-15db at 80Hz
+/-15db at 80Hz
300Hz to 6KHz
300Hz to 6KHz
+/-12db
+/-12db
-0db to +18db
Greater than 80db
18Khz
150watts @ 8 ohms/300watts @ 4ohms
Thermal shutdown/short circuit protect
Variable 0db to +6db
-20dbu typical
15 pin D-Sub
4 amps peak / 2 amps typical
4 amp-120 volt / 2 amp-220 volt
29” x 11.75” x 9”
40lbs
THETA SPECIFICATIONS
WARRANTY AND SERVICE
The Internal Circuitry is fully guaranteed to be free of defects under normal use and
service for a period of three years from the date of purchase. The Speakers and Cabinet
that are used in this product are fully guaranteed to be free of defects under normal use
and service for a period of three years.
Any damage resulting from the misuse or the failure to follow the precautions and
instructions will void the warranty.
In the event that the unit needs to be repaired, please return the unit to ISP
Technologies directly. Simply repack the unit, send a copy of the original receipt, a note
stating the problem, and send it to:
ISP Technologies, LLC
5479 Perry Drive Unit B
Waterford, MI 48329
Attn: Repair Dept.
All shipping charges must be fully prepaid.
ISP will not be responsible for any damages incurred in shipping of any unit. Any claim
will need to be settled with the shipping company.
The warranty will be voided if the serial number has been tampered with in any way.
The warranty card must also be filled out and returned in order to activate the warranty.
Should you have any questions for the repair department prior to returning the product
please call 1-(248)-673-7790
NOTE: This Product may be covered under one or more of the following patents or
patents pending: 7,035,413; 6,944,305; 6,931,134; 6,831,514; 6,091,013
ISP TECHNOLOGIES, LLC
5479 PERRY DRIVE UNIT B
WATERFORD, MI. 48329
248-673-7790
FAX: 248-673-7696
www.isptechnologies.com
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