ECL86 Preamp

ECL86 PREAMP actually uses PCL86 vacuum tubes in this design. The only difference between them is a heating style. There are two tubes per channel: line preamp and phono preamp. Each vacuum tube has its separated power supply with 330V stabilizator. Entire preamp consists of two separated monoblocks. Moreover, the board of line preamp and phono preamp is a mainboard where board with high precision volume controler and board with input selector and protection are mounted in perpendicular way to it. Left and right block (preamp board + volume controler + inputselector and protections) are designed as mirror image. The great advantage of this construction is that no analog signal is distributed over the box. The high precision volume controler is designed as a resistor net switched by realys. The schematic of line preamp, phono preamp and protections are divided from the original project published in czech journal "Praktická Elektronika". Rest circuitry and all PCBs are designed by author.

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Technical documentation

 

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Theory of Operation of the ECL86 PREAMP and E34L POWER AMP

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Single Ended Class A 300B Power Amp