Harley Benton GPA-400 Stereo Guitar Power Amp User Manual

Harley Benton GPA-400 Stereo Guitar Power Amp

Product Information

GPA-400 Stereo Guitar Power Amp
The GPA-400 is a stereo guitar power amp designed to amplify electric audio frequency signals for use with passive speakers. It is intended for use by individuals with sufficient physical, sensorial, and intellectual abilities and corresponding knowledge and experience. The device should only be used as described in the user manual, and any other use or use under different operating conditions is considered improper and may result in personal injury or property damage.

The product features include:

• Amplification of electric audio frequency signals
• Stereo configuration
• Compatible with passive speakers

Product Usage Instructions

Safety Instructions
Before using the GPA-400 Stereo Guitar Power Amp, please read and follow these safety instructions:

1. Ensure that plastic bags, packaging, etc. are disposed of properly and are not within reach of babies and young children. These items can pose a choking hazard.
2. Ensure that children do not detach any small parts (e.g., knobs) from the unit as they could swallow them and choke. Never children use electrical devices unsupervised.
3. Only use the device as described in the user manual. Using it improperly may result in personal injury or property damage.
4. This device should only be used by individuals with sufficient physical, sensorial, and intellectual abilities and corresponding knowledge and experience. Others should only use the device under supervision or instruction from a responsible person.

General information

This user manual contains important information on the safe operation of the device. Read and follow all safety notes and all instructions. Save this manual for future reference. Make sure that it is available to all persons using this device. If you sell the device to another user, be sure that they also receive this manual.
Our products and user manuals are subject to a process of continuous development. We there‐fore reserve the right to make changes without notice. Please refer to the latest version of the user manual which is ready for download under www.thomann.de.

Further information
On our website (www.thomann.de) you will find lots of further information and details on the following points:

topics of interest for you quickly.
Online guides| Our online guides provide detailed information on technical basics and terms.
Personal consultation| For personal consultation please contact our technical hotline.
Service| If you have any problems with the device the customer service will gladly assist you.

Notational conventions
This manual uses the following notational conventions:

Letterings
The letterings for connectors and controls are marked by square brackets and italics. Examples: [VOLUME] control, [Mono] button.

Symbols and signal words
In this section you will find an overview of the meaning of symbols and signal words that are used in this manual.

immediate dangerous situation that will result in death or serious injury if it is not avoided.
CAUTION!| This combination of symbol and signal word indicates a pos‐ sible dangerous situation that can result in minor injury if it is not avoided.
NOTICE!| This combination of symbol and signal word indicates a possible dangerous situation that can result in material and environmental damage if it is not avoided.
Warning signs| Type of danger
---|---
| Warning – high-voltage.
| Warning – danger zone.

Safety instructions

Intended use
This device amplifies electric audio frequency signals to operate passive speakers. Use the device only as described in this user manual. Any other use or use under other operating con‐ditions is considered to be improper and may result in personal injury or property damage. No liability will be assumed for damages resulting from improper use.
This device may be used only by persons with sufficient physical, sensorial, and intellectual abilities and having corresponding knowledge and experience. Other persons may use this device only if they are supervised or instructed by a person who is responsible for their safety.

Safety
DANGER!
Danger for children
Ensure that plastic bags, packaging, etc. are disposed of properly and are not within reach of babies and young children. Choking hazard! Ensure that children do not detach any small parts (e.g. knobs or the like) from the unit. They could swallow the pieces and choke! Never let children unattended use electrical devices.

DANGER!
Electric shock caused by high voltages inside
Within the device there are areas where high voltages may be present. Never remove any covers. There are no user-serviceable parts inside. Do not use the device if covers, protectors or optical components are missing or damaged.

DANGER!
Electric shock caused by short-circuit
Always use proper ready-made insulated mains cabling (power cord) with a protective contact plug. Do not modify the mains cable or the plug. Failure to do so could result in electric shock/death or fire. If in doubt, seek advice from a registered electrician.

CAUTION!
Possible hearing damage
With loudspeakers or headphones connected, the device can produce volume levels that may cause temporary or permanent hearing impairment. Do not operate the device permanently at a high volume level. Decrease the volume level immediately if you experience ringing in your ears or hearing impairment.

NOTICE!
Risk of fire
Do not block areas of ventilation. Do not install the device near any direct heat source. Keep the device away from naked flames.

NOTICE!
Operating conditions
This device has been designed for indoor use only. To prevent damage, never expose the device to any liquid or moisture. Avoid direct sunlight, heavy dirt, and strong vibrations. Only operate the device within the ambient conditions specified in the chapter.
‘Technical specifications’ of this user manual. Avoid heavy temperature fluctuations and do not switch the device on immediately after it was exposed to temperature fluctuations (for example after transport at low outside temperatures). Dust and dirt inside can damage the unit. When operated in harmful ambient conditions (dust, smoke, nicotine, fog, etc.), the unit should be maintained by qualified service personnel at regular intervals to prevent overheating and other malfunction.

NOTICE!
Power supply
Before connecting the device, ensure that the input voltage (AC outlet) matches the voltage rating of the device and that the AC outlet is protected by a residual current circuit breaker. Failure to do so could result in damage to the device and possibly injure the user. Unplug the device before electrical storms occur and when it is unused for long periods of time to reduce the risk of electric shock or fire.

NOTICE!
Possible damage due to installation of a wrong fuse
The use of different types of fuses can cause serious damage to the unit. Fire hazard! Only fuses of the same type may be used.

Features

• Maximum output power 400 W @ 8 Ω
• Operating modes: Bridged Mono, Stereo
• Volume, Resonance and Presence adjustable per channel
• Fanless operation

Installation and starting up

Unpack and check carefully there is no transportation damage before using the unit. Keep the equipment packaging. To fully protect the product against vibration, dust and moisture during transportation or storage use the original packaging or your own packaging material suitable for transport or storage, respectively.
Create all connections while the device is off. Use the shortest possible high-quality cables for all connections. Take care when running the cables to prevent tripping hazards.

NOTICE!
Magnetic fields
The device generates strong magnetic fields that can interfere with the function of poorly shielded devices. The strongest magnetic fields are directly above and below the power amplifier. Therefore, never place sensitive devices such as pre-amplifiers, radio transmission systems, or tape decks directly above or below the power amplifier. When installing the power amplifier into a rack, you should place it in the lowest position, and further equipment such as pre-amplifiers in the highest position.

Rack mounting
The unit has been designed for rack mounting in a standard 19-inch rack; it occupies one rack unit.

Tips on handling speakers
We recommend you to set up the speakers in a way, that the sound signals can reach the audience unobstructed. It will often be helpful to mount the speakers on tripods. Thus, the sound will be evenly spread with maximum range throughout the audience area.
Always use high grade cable to connect your equipment. Otherwise you won’t reach maximum sound quality.
For optimum results both impedance and power handling of the speakers must match the requirements of the amplifier. Always follow the technical specifications of the speakers! The overall impedance of the connected loudspeakers must not decreed the minimum output impedance of the amp. The amps max. RMS output power should be 50 % above the power handling capacity of the connected speakers.
If you notice distortion during operation, either the amp or the speaker is overloaded. This may permanently damage the amp or the speaker. Always reduce the volume when you hear distortion.

Additional useful tips
Available operating modes
Depending on the respective application, the guitar amp can be used in various modes:

Stereo

| Both power amp channels operate independently of each other, each input (CHA and CHB) is amplified by one channel, speakers are connected to both channels, the volume for both outputs can be controlled sepa‐ rately.
Bridged
| Both power amp channels are internally wired for pro‐ viding double the output power. Only the signal from input CHA is amplified, speakers are only connected to the accordingly labelled output. Use volume control CHA to adjust the volume.

On each output of the amplifier, the overall impedance resulting from the individual impedances of the connected speakers must not fall below the minimum allowable impedance of the amp’s output. If you want to connect multiple speakers to one amplifier output, note the following:

• when connecting speakers in series, the impedances add up.
• when connecting speakers in parallel, the reciprocal value of the total impedance is equal to the sum of the reciprocal values of the individual impedances.

This means, for example with two speakers with the same impedance: In series connection, impedance is doubled. In parallel connection, it’s halved.
Detailed information on this topic can be found in our online guide ‘Speakers’ (www.tho‐mann.de).

Connections and operating elements

Front panel

1| [POWER ON | OFF] | mains switch to turn the device on and off
---|---
2| [VOLUME] | volume control for channel A
3| [RESONANCE] | resonance control for channel A
4| [PRESENCE] | presence control for channel A
5| [SIGNAL] | indicator LED (green). This LED lights up when the device is turned on and a signal is present in channel A.
6| [PEAK] | indicator LED (red). This LED lights up when channel A is overloaded by an excessive input signal.
7| [BRIDGE] | indicator LED (yellow). This LED lights up when the device is operating in bridged mode.
8| [MUTE] | switch to mute the device. The white indicator LED lights up when the device is muted.
9| [PEAK] | indicator LED (red). This LED lights up when channel B is overloaded by an excessive input signal.
10| [SIGNAL] | indicator LED (green). This LED lights up when the device is turned on and a signal is present in channel B.
11| [VOLUME] | volume control for channel B
12| [RESONANCE] | resonance control for channel B
13| [PRESENCE] | presence control for channel B

14| [INPUTS] | input sockets for channels A and B
---|---
15| [Mono Bridge|Stereo] | switch to toggle between bridged mono operation via channel A and stereo operation via channels A and B
16| [OUTPUTS CHA] | output sockets to connect a passive speaker box in bridged mono mode (channel A)
17| [OUTPUTS CHB] | output sockets to connect a second passive speaker box in stereo mode (channels A and B).
18| IEC chassis plug with fuse holder

Technical specifications

10 kΩ (unbalanced)
Output power| 16 Ω, stereo| 2 × 50 W
8 Ω, stereo| 2 × 100 W
4 Ω, stereo| 2 × 200 W
16 Ω, bridged| 200 W
8 Ω, bridged| 400 W
Frequency response| 20 Hz … 20 kHz
Signal-to-noise ratio| > 90 dB
Total harmonic distortion (THD)| < 0.15 %
Cooling| fanless
Damping factor| > 80
Sensitivity| 335 mV
Gain| 39.5 dB
Slew rate| 8 ms
---|---
Power consumption at 1/8 rated power| 70 W (max. 300 W)
Operating supply voltage| 230 V    50 Hz
Fuse| 5 mm × 20 mm, 2,5 A, 250 V, slow-blow
Dimensions (W × H × D)| 482 mm × 44 mm × 250 mm
Weight| 3 kg
Ambient conditions| Temperature range| 0 °C…40 °C
Relative humidity| 20 %…80 % (non-condensing)

Plug and connection assignment

Introduction
This chapter will help you select the right cables and plugs to connect your valuable equipment in such a way that a perfect sound experience is ensured.
Please note these advices, because especially in ‘Sound & Light’ caution is indicated: Even if a plug fits into the socket, an incorrect connection may result in a destroyed power amp, a short circuit or ‘just’ in poor transmission quality!

Balanced and unbalanced transmission
Unbalanced transmission is mainly used in semi-professional environment and in hifi use. Instrument cables with two conductors (one core plus shielding) are typical representatives of the unbalanced transmission. One conductor is ground and shielding while the signal is transmitted through the core.
Unbalanced transmission is susceptible to electromagnetic interference, especially at low levels, such as microphone signals and when using long cables.
In a professional environment, therefore, the balanced transmission is preferred, because this enables an undisturbed transmission of signals over long distances. In addition to the conduc‐tors ‘Ground’ and ‘Signal’, in a balanced transmission a second core is added. This also transfers the signal, but phase-shifted by 180°.
Since the interference affects both cores equally, by subtracting the phase- shifted signals, the interfering signal is completely neutralized. The result is a pure signal without any noise interference.

1/4″ TS phone plug (mono, unbalanced)

1/4″ TRS phone plug (stereo, unbalanced)

Cleaning

Fan grids
The fan grids of the device must be cleaned of any contamination, such as dust, etc. on a regular basis. Before cleaning, switch off the device and disconnect mains-operated devices from the mains. Only use pH-neutral, solvent-free and non-abrasive cleaning agents. Clean the unit with a slightly damp lint-free cloth.

Protecting the environment

Disposal of the packaging material
For the transport and protective packaging, environmentally friendly materials have been chosen that can be supplied to normal recycling.
Ensure that plastic bags, packaging, etc. are properly disposed of.
Do not just dispose of these materials with your normal household waste, but make sure that they are collected for recycling. Please follow the notes and markings on the packaging.

Disposal of your old device
This product is subject to the European Waste Electrical and Electronic Equipment Directive (WEEE) in its currently valid version. Do not dispose with your normal household waste.
Dispose of this device through an approved waste disposal firm or through your local waste facility. When discarding the device, comply with the rules and regulations that apply in your country. If in doubt, consult your local waste disposal facility.

GPA-400
Stereo Guitar Power Amp

References

• mann.de – Was für Männer!

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