MagnetoSound said:You might try just increasing C3 and C7. It looks like these are already rolling off some highs.
C6 provides a ground path for the node where these caps meet, they act as shunts on the signal before the drivers.
If you really want to use feedback at the FET stage, you can do what Gary suggests and add a small cap from drain to gate. (You don't need a second NFB path on the source leg, because the signal there will reflect the drain signal anyway.)
There is actually some positive feedback between the source and gate, by virtue of the divider node that the gate resistor is connected to.
maye4 said:Other than what you said,wil it help to bypass the biasing resister using a capacitor?Just as C4 in v67 circuit.
You might try just increasing C3 and C7. It looks like these are already rolling off some highs.
RuudNL said:I have done some measurements on this circuit: http://www.groupdiy.com/index.php?topic=51769.0
The best way to 'tame' the HF boost, is to add a capacitor between the drain and the source of the FET.
Try 33 or 47 nF first, listen and increase or decrease the value.
You might try just increasing C3 and C7. It looks like these are already rolling off some highs.
Those capacitors are mainly there to block (V)HF. You would have to increase them to an unrealistic high value to get an audible effect on the HF response.
RuudNL said:IMHO the fact that the "ChinaMod+U87hybrid" modification only influences the drain, causes an unbalance to the output.
What you do to the drain affects the signal current through the FET. It is reflected at the source.
RuudNL said:What you do to the drain affects the signal current through the FET. It is reflected at the source.
No. If you want to see it, simply build the FET stage and connect an oscilloscope to the drain and the source.
You will see that if you increase the frequency, the (AC) voltage on the drain will drop.
The voltage on the source however will remain the same, because it is a source follower. ( A ~ 1 x)
This causes an unbalanced signal.
maye4 said:It acts like a dynamatic EQ!
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