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Marantz discrete op amp (line stage or headphone amp)

Posted 10th November 2013 at 11:00 AM by rjm (RJM Audio Blog)
Updated 10th November 2013 at 01:11 PM by rjm

Last one for today.

I was having problems getting this to work, the key seems to be adjusting R6 to null the voltage offset. Works fine now, but this is just a rough reverse engineer of the diagram, the parts values and the type of transistors are essentially placeholders.

The input jFET is shown as a dual package. The output bias current is most likely much lower than the 100 mA I configured, so the class A output power is proportionately smaller. For the rest of the currents and the types of transistors used, your guess is as good as mine.

edit: R7 should most likely be closer to 47 ohms, while another 5p capacitor should go in parallel with the feedback resistor, R17.
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Old

The Pentamond

Posted 10th November 2013 at 05:17 AM by rjm (RJM Audio Blog)

A rainy and cold afternoon here in Kyoto. The mind turns to audio circuits... headphone amplifiers... diamond buffers...

This is an answer to the question of how you scale up the basic diamond buffer circuit to higher output currents without making any modifications to the driving transistor pair.

You just add more outputs in parallel.

It seems to work pretty well under simulation.
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