Hafler 0915P manual Balance Controls, Muting System Power Supply

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JFET BUFFER AND RECORD OUTPUT

DRIVER

TAPE MONITOR

SWITCHING

VOLUME AND

BALANCE CONTROLS

LINE AMPLIFIER

TONE CONTROL SYSTEM

MUTING

SYSTEM

POWER SUPPLY

The output of the Selector System is followed by a very high input-impedance JFET buffer pair to establish negligible CMOS switch loading (for low distortion) and to provide a low-impedance source for the Record Output and the Volume and Balance controls.

The Tape Monitor Switch drives a relay to break the line input path to insert tape input signals. The relay employs gold plated contacts, and allows optimum signal routing by placing the relay close to the Tape Input jacks and the Input Selector System.

The Volume Control is a precision detented potentiometer employing laser-trimmed elements for precise channel-balance tracking and a multi-finger wiper for smooth action, prolonged life, and minimum contact noise. The center-detented Balance Control yields channel balance within 0.1 dB in its center position.

The 915 Line Amplifier is a Class-A JFET design employing a differential input stage, driving a complementary high gain output stage, symmetrically driven for balanced slew-rate and low harmonic distortion. This topology uses only four active devices per channel and extremely short loop feedback, yielding high bandwidth and excellent stability.

The feedback loop contains two user selectable paths: one conventional path for flat response, and another path allowing insertion of a tone control network. This arrangement allows maximally

flat response and the shortest, cleanest signal path when tone control action is not required.

The output of the Line Amplifier is capacitor coupled to the outputs of the preamplifier.

The Tone In Switch allows complete removal of the tone controls from the signal path. This switching is accomplished with the same type of CMOS-FET electronic switch used for the Input Selector. This switching arrangement eliminates signal degradation due to mechanical switch contacts, and allows the electronic switch to be located very close to the Line Amplifier circuitry.

The Bass Control is of a moving inflection, variable turnover type, and the Treble Control is of a shelving, variable turnover type. These types of tone controls offer the best “tools” for modifying tonal balance without introducing unwanted side effects.

The Muting System monitors the difference between the raw (unregulated) power supply voltage and the regulated power supply voltage. During the power-up cycle, the Audio and Headphone Outputs are muted until the difference between the unregulated and regulated voltages reaches a predetermined level, and then remain muted for several seconds to allow all circuitry to stabilize. During power-down, or in cases of excessively low AC line voltage, the Audio and Headphone Outputs are instantly muted to avoid extraneous noises.

The muting is accomplished by grounding the output of the Line Amplifier, using a relay with gold contacts.

The printed circuit board mounted power transformer utilizes dual primaries for worldwide operation. Internal jumpers configure the power supply for rated operation from 100 to 120 VAC, or 200 to 240 VAC, at 50 or 60 Hz. A generous amount of power supply headroom allows actual operation over much wider ranges of 85 to 130 VAC, or 170 to 260 VAC.

The power transformer feeds a conventional split full wave bridge rectifier system. Power supply capacitance is 4700 pF per rail. Stable and consistent ± l5 volt power for the amplifier circuits is

provided by three-terminal heatsink-mounted regulators. Further local power supply filtering of 470 UF per rail is provided for each channel of the Line and Phono Amplifiers. All electrolytic filter capacitors are bypassed by high quality film capacitors.

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Contents Series AI0 Service personnel Has been exposed to rain, orNot Performance, orTable of Contents Performance Specifications Phono SectionREC OUT Line Amplifier Headphone AmplifierInstallation Placement Line VoltageOPERATION/CONNECTIONS RackmountingLine Level Inputs Phono Section Preamplifier Front Panel View Preamplifier Rear Panel View Volume Control Balance OUT 1, OUT 2 and Output OFF Switch Headphone Circuit DescriptionMuting System Power Supply Balance ControlsAdditional Information Installation of Optional Phono Printed Circuit Board Refer Diagram Above Described switching arrangements will remain the sameIt. Only CanInstallation of Optional Cartridge Loads Or install this Tone switchBottom covers. Remove covers JumperOr buzz Paths For aUse Plug! It mayPreamplifier Functional Block Diagram Parts List Main Circuit Board Wvuwla mom lN3NOdW03 awoa mm13 Nivw RJoba’ +A--------L’ Board Circuit Schematic Parts List Phono Board Phono Board Component Layout Diagram Phono Board Circuit Schematic Diagram Service Policy and Limited Warranty Difficulty or have any question

0915P, 915 specifications

The Hafler 915 and 0915P amplifiers are remarkable products from Hafler, a company known for its high-quality audio equipment. These amplifiers are engineered to deliver precise sound reproduction, making them ideal for both home audio setups and professional applications.

One of the standout features of the Hafler 915 is its robust power output. With a capability of delivering 200 watts per channel into an 8-ohm load, it ensures that even the most demanding speakers can be driven effortlessly. The 0915P model, a variant of the Hafler 915, offers similar power specifications with additional features appealing to both audiophiles and professionals in the audio field.

The amplifiers utilize Hafler's proprietary technologies to provide impressive dynamic range and low distortion levels. The innovative circuitry employed in these models enhances signal integrity, which translates to a more accurate representation of the original audio source. Users can expect high fidelity sound that captures the nuances of music and dialogue with clarity.

Another important characteristic of the Hafler 915 and 0915P is their versatility in connectivity options. The amplifiers come equipped with multiple input configurations, including balanced and unbalanced connections. This flexibility allows them to be integrated seamlessly into various audio systems, whether for studio monitoring or home theater use.

The design of the Hafler 915 and 0915P amplifiers reflects both aesthetic appeal and functional efficiency. Featuring a sleek chassis and a user-friendly interface, these models are not only well-built but also visually pleasing. The robust heat dissipation mechanisms ensure long-term performance and reliability, making them suitable for extended use in demanding environments.

In summary, the Hafler 915 and 0915P amplifiers embody a blend of power, precision, and versatility. Their high-quality sound reproduction capabilities, coupled with innovative technologies and solid construction, make them excellent choices for anyone seeking to elevate their audio experience. Whether in a professional studio or a home audio setup, these amplifiers stand out as top contenders in the realm of audio amplification.
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