Rockford Fosgate 250.1 Technical Design Features, TOPAZ Tracking Operation Pre-AmplifierZone

TECHNICAL DESIGN FEATURES

Many of the solutions to common design problems encountered by Rockford Fosgate engineers created entire new circuit designs as well as new ways to construct the Punch 250.2 and 250.1 Power Amplifiers. In our flagship amplifiers, no expense was spared in design and construction from the unique circuitry design to the manufacturing process that has proven to be the industry reference for many years. Described below are just some of the accomplishments achieved by our engineering and manufacturing staff.

◆trans•nova (TRANSconductance NOdal Voltage Amplifier)

The trans•nova (TRANS conductance NOdal Voltage Amplifier) is a patented circuit (U.S. Patent 4,467,288) that allows the audio signal to pass through the amplifier at low voltage. Each amplifier channel utilizes its own “fully floating” power supply and is configured to increase power gain. The increase in power gain allows the drive stage to operate at a lower voltage. A low voltage drive stage is the same principle used in high quality preamplifiers to produce high linearity and wide bandwidth.

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	trans•nova circuitry

The resulting design utilizes an output stage with a simpler gain structure and a shorter total signal path than conventional high voltage (bi-polar) designs. The number of stages is reduced from five or more to three. The output stage is further refined into a trans-impedance stage (current to voltage converter) to achieve a short loop (fast) negative feedback. The output stage is driven cooperatively by a transconductance stage (voltage to current converter).

THE RESULT: Superior sound quality, greater efficiency and higher reliability.

◆DIABLO (Dynamically Invariant A-B Linear Operation)

DIABLO (Dynamically Invariant A-B Linear Operation - patent application in process) is an important advance in circuit design which reduces high frequency distortion. Amplifiers which utilize a large array of output MOSFETs cause a high capacitive load on the driver stage. This load can make the high frequencies sound harsh. The DIABLO circuit eliminates high frequency distortion by allowing the driver to operate with 20dB or more of current headroom, whereas traditional drives have only 6dB of current headroom.

THE RESULT: Lower distortion and greater inherent stability.

◆TOPAZ (Tracking Operation Pre-Amplifier Zone)

The TOPAZ (Tracking Operation Pre-Amplifier Zone) circuitry solves ground loop noise problems common to automotive amplifier design. This innovative new development allows vastly improved isolation of the input signal grounds from the power supply ground of the amplifier. This is accomplished by allowing the source unit to control the potential “environment” of the entire input structure or “zone” of the amplifier. This process improves the noise rejection of the amplifier by 30-40dB – an astounding 20-100 times better than amplifiers without TOPAZ.

THE RESULT: Elimination of troublesome ground loop noise between source and amplifier.

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