Acoustic 450 User manual

Note: This owner’s manual for the Acoustic 450 has been reconstructed from digital scans of an
original manual, run through OCR software and reconstituted into a printable document. Every effort
has been made to retain the content integrity of the original document. Thanks Julien for the files.
OWNER'S MANUAL
control corporation
MODEL 450
LEAD / BASS AMPLIFIER
acoustic control corporation
7949 Woodley Avenue
Van Nuys, Ca. 91406
[phone]
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A WORD TO ACOUSTIC AMPLIFIER OWNERS
We would like to take this opportunity to thank you for choosing an ACOUSTIC product and to assure you
of our continuing interest in your musical pleasure and satisfaction.
This manual has been prepared to acquaint you with the proper operation of your amplifier and to provide
important information as to its many capabilities. We urge you to read it carefully and follow the
recommendations contained to help assure the most enjoyable and trouble free operation of your amplifier.
When it comes to service, remember than an authorized ACOUSTIC Service Center knows your amplifier
best and is interested in your complete satisfaction.
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TABLE OF CONTENTS
Page
ACOUSTIC LIFETIME WARRANTEE 4
GENERAL DESCRIPTION 5
MODEL 450 - SPECIAL FEATURES 6
1. Lead / Bass Selector Switch 6
2. Special Output Circuit Configuration 6
3. Auxiliary Volume Control 6
4. Use Outside the United States 6
FRONT PANEL VIEW 7
OPERATION OF CONTROLS and CONNECTIONS 8
CONNECTIONS 8
1. Input 1 8
2. Input 2 8
3. Bright Switch 8
4. Volume 8
5. Treble 8
6. Mid-Range 8
7. Bass 8
8. Distortion Control 9
9. Auxiliary Volume Control 9
10. Ground Reverse Switch 9
11. Lead / Bass Selector Switch 9
12. Power On / Off Switch 9
13. Graphic Equalizer 10
How the Graphic Equalizer Works
How to Use the Graphic Equalizer
REAR PANEL VIEW 11
14. Speaker Output Jack 1 12
15. Speaker Output Jack 2 12
16. Booster Output 12
17. Line Outputs 12
18. Accessory Jack 13
19. Footswitch Connector 13
20. Fuse 13
21. AC Convenience Outlet 13
22. AC Line Cord 13
A NOTE ON SPEAKER IMPEDANCES 14
MODEL 450 PHYSICAL SPECIFICATIONS 15
MODEL 450 ELECTRICAL SPECIFICATIONS 16
AMPLIFIER LINE VOLTAGE REQUIREMENTS
FOR OPERATION IN U.S.A. AND FOREIGN COUNTRIES 18
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ACOUSTIC LIFETIME WARRANTY
Acoustic Control Corporation guarantees its products to the original purchaser to be free from all defects in
materials and workmanship.
THIS LIFETIME GUARANTEE IS VALID ONLY IF THE WARRANTY REGISTRATION CARD IS
COMPLETED AND MAILED TO ACOUSTIC WITHIN 10 (TEN) DAYS FROM THE DATE OF PURCHASE.
Acoustic Control Corporation will validate the Warranty and return it to you for your files. The card MUST be
validated for your warranty to be in effect.
Should an Acoustic product require service, the purchaser must take the product to an authorized
ACOUSTIC Service Center for repair in order for the Warranty to be effective. A list of these centers is
provided in the back of this manual. Once the produce has been delivered to the Service Center, all repairs
will be made free of any charge to the original purchaser, provided the product has not been misused or
mishandled.
IMPORTANT
It is necessary for your ACOUSTIC product to be registered in the event it should ever require service. In
order to register your new Acoustic product and receive the Acoustic Life-Time Warranty, fill out both
sections of the Warranty card and return it to Acoustic within 10 (ten) days of the purchase date. PLEASE
PRINT LEGIBLY. The first part of the card will be kept in our files. The second part will be validated and
returned to you. The card must be validated for your Warranty to be in effect.
To avoid unnecessary expense, an owner who desires service on a piece of equipment must always bring
the validated Warranty card to the authorized Acoustic Service Center when the equipment is taken there.
If the card is not presented at that time, a phone call, at the owner's expense, will have to be made to the
factory to establish a valid Warranty on the equipment.
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GENERAL DESCRIPTION
ACOUSTIC's Model 450 is a versatile guitar amplifier with many special features that produces 170 Watts
RMS power into a 4 ohm speaker with less than 5% distortion. The Lead/Bass switch located on the front
panel is unique in that it allows the amplifier to be used as either a lead guitar or a bass guitar amplifier.
Besides having a quality sound and a powerful sound system, the Model 450 excels in flexibility due to its
advanced engineering. The location and function of each control is clearly described in this manual. To
utilize the full capability of this instrument, it is again recommended that you READ THIS OWNER'S
MANUAL thoroughly.
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MODEL 450-SPECIAL FEATURES
1. LEAD/BASS SELECTOR SWITCH
The LEAD/BASS switch located on the front panel allows the amplifier to be used as either a lead
guitar or a bass guitar amplifier. The amplifier in the LEAD switch position is a wide-band flat
amplifier. It reproduces fundamental tones plus harmonics. This is most desirable when playing a
lead guitar. When used in the BASS position, the harmonics are restricted. All harmonics beyond
1200 Hz are de-emphasized, a desirable characteristic when playing a bass guitar. The
LEAD/BASS selection is made in the output section of the circuit which makes the LEAD/BASS
conversion effective even when the amplifier is being overdriven or when it is used in the distort
mode.
2. SPECIAL OUTPUT CIRCUIT CONFIGURATION
This provides constant power into the speaker, especially at low bass frequencies, to produce solid
bass characteristics and to augment the higher harmonic frequencies.
3. AUXILIARY VOLUME CONTROL
This control allows you to pre-set two different volume levels and switch between them with the foot
switch.
4. USE OUTSIDE THE UNITED STATES
If you wish to use your amplifier outside the United States, voltage selection can be made with slide
switches that are located inside the back of the amplifier. (You must remove the cover to make the
voltage selection.) The amplifier's various operating voltages are 107V, 120V, 210V, and 240V, all
at 50 or 60 Hz.
CAUTION: Even though the switches are clearly marked, it is suggested that your dealer's service
department make the adjustment.
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OPERATION OF CONTROLS AND CONNECTIONS
1 & 2 INPUTS
There are two input jacks on the left side of the front panel. The top input is louder than the bottom input.
The top input should be used in most cases to achieve maximum signal-to-noise ratio. If your instrument
puts out such a large signal that you can turn the volume control only slightly above the off position, then
you should use the second input to cut down on the signal. The difference between the two inputs is
volume gain. Input 2 is 10 dB lower than input 1.
3 BRIGHT SWITCH
In the BRIGHT position, the treble is boosted in relation to the bass and mid-range. This enables you to
achieve a crisper sound.
4 VOLUME
The Volume control increases the volume of all frequencies and special functions equally.
5 TREBLE
The Treble control is for control of upper-range tones. The tone circuitry is of the cut and boost type as
opposed to the straight boost varieties. This control enables you to compensate more easily for most pick-
up devices. Always keep in mind that flat (or normal) is with the knob pointer straight up.
6 MID-RANGE
The Mid-Range control is for the control of middle-range tones. The tone circuitry is of the cut and boost
type as opposed to the straight boost varieties. This enables you to compensate more easily for most pick-
up devices. Always keep in mind that flat (or normal) is straight up. Note: This control can also be used as
part of Graphic Equalizer for frequencies between 460 to 700 Hz.
7 BASS
The Bass control is for low-range tones. The Bass tone circuitry is also of the cut and boost type. This
allows you to obtain maximum "bottom" even if the instrument is weak in Bass response. This control is
very active and when used in conjunction with the Graphic Equalizer allows you an infinite variety of tone
settings. Flat (or normal) is straight up.
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OPERATION OF CONTROLS AND CONNECTIONS, continued
8 DISTORTION CONTROL
This control is used to create a desired amount of distortion. Distortion is somewhat similar to the sound
effect known as "fuzz." When the distortion control is turned fully counter clockwise, the distortion circuit is
bypassed. To obtain the desired distortion effect, advance the control knob to the right until the desired
effect is achieved. The distortion circuit is electronically switched in and out with the foot switch while
playing. Electronic switching eliminates clicks.
9 AUXILIARY VOLUME CONTROL
This control allows you to pre-set two different volume levels: one primary and the other secondary. Use
the master Volume Control (4) to set the primary level, then press the foot switch down and set the
secondary level with the Auxiliary Volume Control. The foot switch selects between primary and secondary
volume levels. Again, switching is done electronically, therefore there are no clicks and pops that would
interfere with your playing. This control enables the musician to switch with ease back and forth from lead
playing to rhythm playing.
10 GROUND REVERSE SWITCH
Many times you will have a persistent hum or buzz from the guitar strings. The Ground Reverse Switch has
been designed to reduce or eliminate this condition. Set the Switch in whichever position reduces or
eliminates the problem.
11 LEAD/BASS SELECTOR SWITCH
The amplifier in the LEAD Switch position operates as a wide-band flat amplifier. It reproduces fundamental
tones plus the harmonics. This is desirable when playing a lead guitar. When the Switch is used in the
BASS position, the harmonics are restricted. Any harmonics that are more than 1200 Hz are de-
emphasized, a desirable characteristic when playing a bass guitar. The LEAD/BASS selection is made in
the output section of the circuit making the LEAD/BASS conversion effective even when the amplifier is
being overdriven or when used in a distort mode.
12 POWER ON/OFF SWITCH
This Switch turns the entire system On. There may be a moderate thump when you turn the amplifier On.
DON'T PANIC. This is normal. The "On" condition of the amplifier is indicated by the indicator light built into
the switch button.
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OPERATION OF CONTROLS AND CONNECTIONS, continued
13 GRAPHIC EQUALIZER
The ACOUSTIC Graphic Equalizer is a unique device for musical instrument amplification similar in
function to a studio equalizer. The Equalizer divides the guitar signal into five sections. Section 1 covers the
50 Hz to 110 Hz range; Section 2 covers the 110 Hz to 220 Hz range; Section 3 covers the 220 Hz to 460
Hz range; Section 4 covers the 700 Hz to 1500 Hz range; and Section 5 covers the 1500 Hz to 2800 Hz
range. These slide controls allow you to boost or cut any of these ranges. The Mid-Range control can be
used to cover the 460 Hz to 700 Hz range. You can shape the response of the amplifier to meet your exact
requirements for a particular song. A flat response (no equalizer boost or cut) is achieved when all 5
controls are centered at "0". There is a special mechanical notch on the control to identify this location so
that this adjustment can be felt without referring to the markings.
How the Graphic Equalizer Works.
Let's take a moment and discuss the typical electric guitar. The actual range of the fundamental notes is
from 84 Hz to about 670 Hz. (The open low E string is about 84 Hz, and the E at the twelfth fret of the first
string is about 670 Hz.) The important harmonic overtones occur from about 180 Hz to about 2200 Hz. It is
the balance between the fundamental notes and their harmonic overtones that determines the type of
sound you get. You probably haven't realized it, but you have been aware of this balance and controlling it
to a limited degree for years. How? If your guitar has two pickups, you use the front pickup when you want
fundamentals and heavy bottom. You use the back pickup when you want more overtones. Using your
fingers gives you more fundamentals; using a pick gives you more overtones.
The Graphic Equalizer is a logical extension of this fundamental-to-harmonic balance control. With all this
in mind, let's look at the Graphic Equalizer and see how it applies.
Section 1 (50 Hz to 110 Hz) covers all the notes on the E (sixth) string and about half of the notes on the A
string. It also covers the range about one-half octave below the low E in case you are into Modal or slack
tunings.
Section 2 (110 Hz to 220 Hz) covers all the notes on the D and G strings as well as half the notes on the B
string.
Section 3 (220 Hz to 460 Hz) covers some of the notes on the B string as well as most of the notes on the
High E string. Use the mid-range control for the highest notes of the high E string.
Section 4 (700 Hz to 1500 Hz)covers the second harmonics of the E string.
Section 5 (1500 Hz to 2800 Hz) covers the second harmonics of the high strings and higher harmonics on
the middle strings.
Continues after diagram ….
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OPERATION OF CONTROLS AND CONNECTIONS, continued
Each section boosts or cuts only the notes covered by that section. Everything else stays the same.
Raising the section above the center line boosts or emphasizes certain tones; lowering the section below
the center line cuts or attenuates those same tones. When the section control is centered, the effect of the
section is out of the circuit.
How to Use the Graphic Equalizer
Let's assume for one song you want a really heavy, but not boomy, bass sound with a little bit of snap to
the highs. Try setting the treble control at about 3 o'clock. This gives you the boost to the highs for a little
more snap. Now set the bass control at about 3 o'clock to get a heavy bottom end. Lower the 320 Hz
section (Section 3) to its lowest position (full cut). This removes the objectional boomy overtones from the
sound and lets the bottom and highs come through. Without changing any of the other settings, bring the
320 Hz (Section 3) back to the center and lower the 160 Hz section (Section 2). The change in sound which
you will hear is that of the upper harmonics coming in and the lower set of harmonics being eliminated.
Let's try another one. Set the Bright Switch to the Bright position and set the treble control at about 3
o'clock. Set the bass control to straight up. Put the 160 Hz section to its full boost position (all the way up).
Turn the mid-range control clockwise to full boost. Let's see what we have achieved. Lots of treble so we
have good punchy highs; a flat bass and, in addition, we have boosted the volume of the middle strings as
well as the middle set of harmonics. It is very close to the sound of a tube-type amplifier in its overloaded
position. Remember, when you are setting the amplifier to get a certain sound, use the treble, mid-range,
and bass controls to get the basic sound, then modify it with the Graphic Equalizer to get the exact sound
you desire.
14 & 15 SPEAKER OUTPUT JACKS
Connect your speaker plug into one of the jacks. The other jack is provided in case you need to use
another speaker.
16 BOOSTER OUTPUT
This jack would be used if you desire to drive an additional power amplifier and speakers using the Model
450 head to control the extra amplifier.
17 LINE OUTPUT
This jack is tied to the output of the preamplifier. As the volume is lowered, the output of this jack is
lowered. This jack should be used if you desire to control a bank of power amps and associated speakers
from one main control amplifier. This jack cannot drive a speaker directly.
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OPERATION OF CONTROLS AND CONNECTIONS, continued
18 ACCESSORY JACK
A three-conductor phone jack allows you to route the signal out through and in from any accessory
equipment such as a wah-wah pedal, echo machine, etc. The accessory jack maintains an internal
connection for normal use when no plug is inserted in it.
19 FOOTSWITCH CONNECTOR
A 3 circuit phone-type connector connects the distort and the auxiliary volume footswitch to the amplifier.
20 FUSE (See page 18 for fuse rating)
Keep in mind that a Fuse is simply a circuit breaker that operates if a potentially dangerous situation exists.
If the fuse does blow, always replace it with the proper 5 amp (3AG) SIo-Blo fuse at 125 Volts. Do not use
any other type or rating. When operating at 214 or 240 Volts, use a 3 Amp SIo-Blo 3 AB fuse.
21 AC CONVENIENCE OUTLET
This outlet will provide AC power for auxiliary equipment. Do not plug equipment into this outlet if the total
power demands exceed the rating marked next to the outlet. The outlet stays on even when the amplifier is
off. (See markings on the chassis.)
22 AC LINE CORD
All Acoustic amplifiers have a three-conductor grounding system which connects the chassis ground to the
line ground. This grounding system eliminates the possibility of shock hazard and hum pick-up. When
Acoustic amplifiers are being used in conjunction with other equipment, make certain that the other
equipment has this standard grounding scheme. Grounding faults in other equipment or when using a
"cheater" plug (a 2 pin ground-eliminating plug) can create the possibility of shock hazard and excessive
hum. In such cases, the stage manager or electrician should be asked to correct the problem.
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A NOTE ON SPEAKER IMPEDANCES
Any impedance between 2 ohms and 4 ohms will give optimum results; that is, 170 Watts RMS.
4 ohms is the best match because with a 4 ohm load, the amplifier runs slightly cooler.
Low Impedances
Use of impedances less than 2 ohms may reduce maximum power output and cause extraordinary heating.
High Impedances
Use of impedances greater than 4 ohms will reduce the maximum power output available and will
enable operation at reduced temperatures.
Multiple Speakers
When using Multiple Speakers, find a series-parallel arrangement so that the total impedance is between
2 ohms and 4 ohms. (Ask your Dealer to show you how to do this.)
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MODEL 450 PHYSICAL SPECIFICATIONS
1. CONNECTIONS
Inputs 2 (1/4" phone jacks,2conductor)
Speaker Outputs 2 (1/4" phone jacks, 2 conductor)
Line Outputs 2 (1/4" phone jacks, 2 conductor)
Booster Output 1 (1/4" phone jack, 2 conductor)
In / Out Accessory 1 (1/4" phone jack, 3 conductor)
Foot Switch Socket 1 (1/4" phone jack, 3 conductor)
Physical Dimensions 24-5/8" W x 7" H x 12-1/2" D
Shipping Weight 30 lbs. + 5 lbs. shipping carton
2. CONTROLS
Volume Rotary Potentiometer
Treble Cut and Boost Rotary Potentiometer
Mid-Range Cut and Boost Rotary Potentiometer
Bass Cut and Boost Rotary Potentiometer
Distort Rotary Potentiometer
Auxiliary Volume Rotary Potentiometer
Bright Switch Rocker Switch
Lead / Bass Switch Rocker Switch
Ground Reverse Switch Rocker Switch
Graphic Equalizer 5 Section (Each section is a slide potentiometer with
detent in the flat position.)
Power On / Off Switch and Pilot Light Push-On / Push-Off Switch
Auxiliary Outlet 3 Conductor Grounded Standard
Fuse 3 Amps SIo-Blo or 5 Amps SIo-Blo
Line Adjustment See page 18
Inside Adjustment See page 18
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MODEL 450 ELECTRICAL SPECIFICATIONS
1. OUTPUT
Power output (continuous) across 4 ohm load
@ less than 5% distortion 170 Watts RMS
Peak power output (instantaneous) across
4 ohm load @ 5% distortion 450 Watts
Power output (continuous) across 2 ohm load
@ 5% distortion 170 Watts RMS
Peak power output (instantaneous) across
2 ohm load @ 5% distortion 400 Watts
2. GAIN (All controls flat volume max.)
Preamp gain (from input to line output) 38 dB or 80X
Total gain 63.5 dB or 1500X
Power amplifier gain from ext. inputs to speaker output 55 dB or 500X
3. SENSITIVITY
Input voltage for maximum output Input 1: 15 mv RMS
Input 2: 45 mv RMS
Input voltage capability (maximum) Input 1: 510 mv RMS
Input 2: 1.6V RMS
Nominal Input impedance Input 1: 470K OHMS
Input 2: 69K OHMS
4. NOISE (all controls flat, inputs shorted)
Noise-to-full-output ratio - volume minimum 78 dB below full output
- volume maximum 78 dB below full output
5. FREQUENCY RESPONSE
At 10 Watt level -3dB, 27Hz to 21KHz
Power bandwidth 1/2 power point 30 Hz to 18K Hz
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MODEL 450 ELECTRICAL SPECIFICATIONS, continued
6. AUXILIARY OUTPUTS
Output Voltage 250 mv RMS
Impedance 5000 ohms
Booster Output 275mv RMS
Impedance 1 K ohms
7. DISTORTION CIRCUIT (all controls flat, distortion control and volume control max.)
Minimum Input Required to Clip Power Amp 425 Microvolts
8. RANGE OF TONE CONTROLS
Bass +15 dB Boost, -15 dB cut @ 50 Hz
Treble +15 dB Boost, -25 dB cut @ 10KHz
Mid-Range +7 dB Boost, -30 dB cut @ 400 Hz
Bright Switch Boost 6 dB per octave from 200 Hz to 5 KHz
9. RANGE OF GRAPHIC EQUALIZER
Section 1 ±16 dB @ 70 Hz
Section 2 ±16 dB @ 140 Hz
Section 3 ±16 dB @ 280 Hz
Section 4 ±16 dB @ 1100 Hz
Section 5 ±16 dB @ 2200 Hz
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AMPLIFIER LINE VOLTAGE REQUIREMENTS
FOR OPERATION IN U.S.A. AND FOREIGN COUNTRIES
1. 107 Volts Line Used when supply line is 100V - 50/60 Hz
Use 5A, 125V Slo-Blo Fuse as in Japan or
Used when supply line is rated 110V
CAUTION: Do not use 107V tap with 120V line
2. 120 Volts Line Used in U.S.A. or where Line Voltage
Use 5A, 125V Slo-Blo Fuse is specified as 117V or 120V - 50/60 Hz Lines
3. 214 Volts Line Used where Line is specified as 210V or
Use 3A, 250V Slo-Blo Fuse 220V AC - 50/60 Hz
(mostly European Countries)
CAUTION: Do not use this tap with 225V,
230V or 240V Lines
4. 240Volts Line Used with 225, 230, and 240 Volts -
Use 3A, 250V Slo-Blo Fuse 50/60 Hz Lines
(many European countries & Australia)
Note: See page 20 for line cord color code details.
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