O P E R A T I O N

POWER SWITCH

The POWER switch is located on the front panel of the amplifier. An internal lamp indicates when it is turned on. Standard practice is to turn the amplifier on last and off first when switching components individually to prevent sending damaging transients, generated in the source components, to the speakers. It is possible to leave the power switch in the on position and switch the amplifier remotely through a power distribution block or preamp switched outlet. When doing so make sure the switch is rated for the current required by the amplifier.

BALANCED/UNBALANCED INPUT SWITCH

The BALANCED/UNBALANCED switch configures the input grounding when using the RCA phono input jacks. In the UNBALANCED position the balanced differential input return (–) port is grounded inside the amplifier. This prevents noise pickup or unstable amplifier operation caused by the open input. In the BALANCED position the differential amplifier inputs are connected to the hot (+) and (–) incoming signal connectors.

GROUND SWITCH

Ground loops are characterized by a hum or buzz in the system and are caused by a voltage potential difference between two points in a ground circuit. Ground loops are aggravated when multiple paths exist for a given circuit. Mounting components in a rack with metal rails may introduce ground loops between associated equipment, because the rails can establish an additional ground path. The CHASSIS/FLOAT switch allows you to select the amplifier grounding scheme for best system compatibility. With the switch in the CHASSIS position all signal grounds are referred to the chassis and power line ground. In the FLOAT position the signal ground is decoupled from the chassis. The position of the switch is determined by the overall noise in the system; choose the position which gives the lowest hum.

MONO SWITCH

Conventional two-channel stereo operation is obtained with the STEREO/MONO switch in the STEREO position. For high powered single channel use, set the switch to MONO and use the left channel input and the RED binding posts only for the output. For thermal considerations we do not recommend using less than an eight ohm load on the amplifier when running it in mono. When the switch is set in the mono position the left channel (+) and (–) inputs are connected to the right channel in reversed polarity, which inverts the right channel output.

LOAD FAULT PROTECTION

Because of the self-protecting properties and fault tolerance of the lateral MOSFETs used in the 9303 and 9505, elaborate voltage and current limiting protection schemes are not necessary. To prevent damage to the amplifier from a fault in the loudspeaker load, the power supply B+ and B– rails are fused. Check these fuses if the sound is garbled or there is no output. The fuses should not blow under normal use and a blown fuse is usually an indication of a fault. The fault could be a bad connection, a problem with the speaker or a short in the speaker line. Disconnect power to the amplifier before removing the cover.

WARM UP

In order to achieve the best sonic performance from the amplifier, we recommend letting it warm up for 1 hour before beginning any critical listening. The amplifier will not deliver its full potential sound quality before this time has passed.

CLEANING AND MAINTENANCE

There is no requirement for regular maintenance on the electronic components of the amplifier. If the case becomes soiled it can be cleaned using a soft cloth and a mild detergent, such as spray window or glass cleaner. If the amplifier is located in a particularly dusty environment cleaning the inside with compressed air or vacuuming every 18 to 24 months is sufficient.

– 3 –

Page 6 Page 8
Page 7
Image 7
Hafler 9505, 9303 manual E R a T I O N, Power Switch
Page 6 Page 8

9505, 9303 specifications

The Hafler 9303 and 9505 are both high-performance power amplifiers that have garnered a solid reputation among audiophiles and professionals in the audio industry. These amplifiers are designed to deliver high-quality sound reproduction with performance and reliability, making them suitable for various audio applications, from home theater systems to professional studio work.

The Hafler 9303 is a versatile amplifier known for its warm sound and consistent performance. With a power output of 100 watts per channel at 8 ohms and 150 watts at 4 ohms, it provides ample headroom for dynamic peaks in music without distortion. The 9303 features a classic, rugged design and is equipped with an exceptional thermal management system to prevent overheating during extended use. Its circuitry incorporates advanced feedback technology that minimizes distortion and enhances audio clarity. The amplifier also supports both balanced and unbalanced inputs, allowing for flexible integration into various audio systems.

On the other hand, the Hafler 9505 takes the performance up a notch with a powerful 200 watts per channel at 8 ohms, and it can reach 300 watts at 4 ohms. This model is ideal for driving larger speakers and can handle demanding audio setups. The 9505 incorporates Hafler's proprietary active feedback design, which maximizes damping factor and ensures accurate transient response. Its robust construction and high-quality components provide longevity and reliability, making it a favorite among professionals who require consistent performance in demanding environments.

Both amplifiers feature dual-mono construction, ensuring independent power supply for each channel, which helps in maintaining channel separation and reducing crosstalk. This design contributes to a wider soundstage and clearer audio reproduction, crucial for critical listening and professional applications. Furthermore, the amplifiers are equipped with comprehensive protection circuitry, safeguarding the components against speaker short circuits and thermal overloads.

In summary, the Hafler 9303 and 9505 power amplifiers represent an excellent choice for anyone seeking reliable and high-fidelity audio performance. With their impressive power outputs, advanced technologies, and robust designs, these amplifiers are versatile enough to cater to both home audio enthusiasts and professional sound engineers, ensuring that they deliver exceptional sonic experiences across various settings.
Top Page Image Contents