Sony TA-N55ES power amplifier

[Tube_Dude]

Originally posted by mikeks


A resistive load for the first stage is a bad idea because it reduces the source impedance ''seen'' by the second stage, and, therefore, compromises current transfer from first to second stage.

This is the mechanism by which overall foward path gain is drastically reduced when changing from an actively loaded first stage to a resitively loaded one.

In this , I stay in complete agreement with you.

My last post only purpose , is of a practical way to check the REAL input impedance of the VAS-TIS , in real world conditions of operation ( my preferred conditions )...

[mikeks]

Originally posted by Tube_Dude


In this , I stay in complete agreement with you.

My last post only purpose , is of a practical way to check the REAL input impedance of the VAS-TIS , in real world conditions of operation ( my preferred conditions )...

Easy: load down interface with large resistor, whose value you reduce until overall foward path gain falls exactly by half.

The impedance modulus at the interface (and at the test frequency) is then equal to the value of the resistor.

[Tube_Dude]

Originally posted by mikeks



Easy: load down interface with large resistor, whose value you reduce untill overall foward path gain falls exactly by half.

The impedance modulus at the interface (and at the test frequency) is then equal to the value of the resistor.

Obviously!