CIRCUIT OPERATION

trans•nova Implementation

The transistor Q1 is configured to operate as a switch which controls the current source, Q103, of the input differential amp, Q6 and Q7. When Q1 is off the emitter voltage is low turning off Q103. Timing of the Soft Start function is controlled by the charging time of C29 through R13. The THERMAL Protection circuit uses Q1 to shut down the channel when excessive heat is detected. The OVERLOAD protection switch Q5 and Q4 turn off Q3 directly when a short is detected on the output.

U1A and U1B are buffer amps configured as unity gain, non-inverting voltage followers which feed the crossover filters U7A and U7B. The feedback components which control the crossover functions are contained on the XCard plug-in module. The output of the filters is fed to the attenuator network controlled by R24. The output of U2A and U7B is connected to the input of the differential amp. U2B is configured as a DC servo integrator to null the input offset currents.

The output of the differential amp is fed to the driver stage by Q17 and Q18 which perform the DIABLO transconductance steering function. The cascode pairs Q9, Q10 and Q11, Q12 supply the signal voltage and current needed to drive the output stage Q30, Q31, Q32, Q33 and Q40, Q41, Q42, Q43. Class AB bias current is controlled by R136. Loop feedback is supplied by the network R1 and C1, and global feedback by R10, C8 and C41.

Adjusting Bias:

The bias control establishes the quiescent Class AB output current of the amplifier. The bias should not need readjustment from the factory setting; however, if the amplifier is repaired and output devices have been changed, or if the two channels of the amplifier do not run at the same temperature, recalibrating the bias is necessary. Disconnect the power to the amplifier before removing the cover. To adjust the bias, disconnect the input and speakers and remove the jumper JW7. Connect an amp meter across the exposed pins. The correct polarity is marked adjacent to the jumper. Adjust R136 to get a current reading of 400mA.

Calibrating Common Mode Rejection:

The input common mode null is adjusted by the trim pot R8. The CMRR should be greater than 75dB below rated output. If the CMRR requires adjustment, feed the amplifier input with a common mode signal and adjust R8. Disconnect the power to the amplifier before removing the cover. Use a sinewave generator set to 1 volt output at 1kHz. Connect the generator signal output to the tip and ring of a 1/4" plug and ground to the sleeve. Plug this into the amplifier input. Connect an AC voltmeter to the amplifier output binding posts. Adjust R8 to give the lowest voltage output from the amplifier. For a temporary adjustment when a signal generator and voltmeter are not available, use an FM tuner and tune it to an unused station as your signal source, and connect the output to the amplifier as described above. Connect the amplifier output to a small full range speaker. Turn the amplifier level controls full down and turn the amplifier on. Turn up the level control until you hear a signal through the speaker. Alternate between adjusting R8 for the lowest output signal and increasing the input control until you have the level control full. There should be a very low output from the amplifier if any is detected at all.

– 13 –

Page 15 Page 17
Page 16
Image 16
Hafler P7000 manual Circuit Operation, Transnova Implementation
Page 15 Page 17

P7000 specifications

The Hafler P7000 is a professional power amplifier renowned for its robust performance and reliability in live sound and studio applications. A cornerstone of the Hafler brand, the P7000 embodies advanced technology and engineering, making it a popular choice among audio professionals.

One of the standout features of the P7000 is its high power output. It delivers up to 700 watts per channel at 4 ohms, providing ample headroom for demanding audio environments. This powerful output makes it suitable for driving large loudspeakers or multiple speaker systems, ensuring clear and dynamic sound reproduction even at high volumes.

The P7000 utilizes a class AB amplifier design, combining the benefits of class A and class B architecture. This design choice ensures low distortion levels while maintaining efficient operation. As a result, users can expect a warm and natural sound with low signal degradation, making the amplifier ideal for critical listening environments.

In terms of build quality, the Hafler P7000 is constructed with durability in mind. The chassis is made from robust materials that can withstand the rigors of frequent transport and use in various settings, from professional studios to live concert venues. Additionally, the amplifier features a well-ventilated design, minimizing overheating and ensuring reliability during extended operation.

The P7000 also includes advanced protection circuitry to safeguard against overload and short circuits. This feature not only protects the amplifier itself but also the connected speakers, providing peace of mind during high-energy performances. Furthermore, the amplifier incorporates a soft start circuit, which gradually ramps up power to the speakers, preventing sudden jolts that could cause speaker damage.

Connectivity is another key aspect of the Hafler P7000. It offers a variety of input options, including XLR and 1/4" TRS connectors, making it compatible with numerous audio sources and easy to integrate into any existing setup. Balanced inputs help reduce noise and interference, ensuring clean signal transfer over long cable runs.

With its combination of powerful output, reliable performance, and versatile connectivity, the Hafler P7000 stands out as a professional-grade amplifier. Whether used in a studio setting or live sound application, it provides audio professionals with the tools they need to achieve exceptional sound quality and consistency.
Top Page Image Contents