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Overview:

The intention of this project was to build simple, but high quality amplifier. The aim was reached by integrating the whole input driver in one IC and adding high power transistor output stage.

OPA552, IRFP240 Dracula 1

Design:

As you can see on the schematic the amplifier has very simple structure. At the input there is high quality and relative high power TI IC OPA552. It drives a complementary pair od MOSFET transistors IRFP240 and IRFP9240. The gain of the whole circut is set to 40x. The TL431 is to set the operation point of output transistors. The idle current is set to 80mA, so the amplifier works in A class for it's first few watts. The more current the longer it stays in A class, but the more power to be dissipated. With 80mA and these heatsinks it still goes very hot after long playing.

OPA552, IRFP240 Dracula 2

The output capacitor is actually unnecessary. It has to change the sound nature. I know it's other electrolityc capacitor in signal path but it's high quality Philips and I like it's sound. The other reason of using it is to perform DC speker protection. The OPA552's are powered from basic regulator using LM317 and LM337 as show on the schematic.

OPA552, IRFP240 Dracula 3

Controller:

It has the same function as mentioned in BridgeClone. The circut performes output relay delay and debouced power on push button with two-colour led. Te whole amplifier can be also remotely power on or off using CNY17 optocoupler on the back panel. Here you can find the schema.

OPA552, IRFP240 Dracula 4

Case:

A standard steel case with aluminium front panel. It was made to fit with my preamplifier and the secound amplifier. I'm going to drive my speakers in bi-amping configuration. Dracula will feed lower frequency band as it have better ability to provide high output current than IC. BridgeClone will drive the other part as it's recommended for it's higher parts.

OPA552, IRFP240 Dracula 5

The back panel is as simple as possible. There are only input, output and power connectors on the back panel. There is also a remote controll socket to be able to turn it on and off from preamplifier. The front panel contains only power on/off push button enlighten with two colour led.

OPA552, IRFP240 Dracula 6

RMAA tests:

Files:

Overview | Design | Controller | Case

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