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RE: Thanks again ...

Posted by andyr (M) on December 24, 2024 at 16:56:19

In Reply to: RE: Buffer - emitter resistor value? posted by 13th Duke of Wymbourne on December 24, 2024 at 13:59:45:

I have the whole circuit (not just the buffer) in LTspice ... so I ran it with, first, 1k as the Emitter resistor - and then 4k7.

Distortion results are as follows:

1k:
Total THD = 0.0654%
* 2nd: 6.541 e-4
* 3rd: 1.690 e-5
* 4th: 6.918 e-7
* 5th: 6.098 e-7

4k7:
Total THD = 0.0580%
* 2nd: 5.802 e-4
* 3rd: 1.677 e-5
* 4th: 6.621 e-7
* 5th: 5.977 e-7

So - as you say - a slight decrease in THD by increasing the Emitter res to 4k7 ... mainly the 2nd harmonic.

So I will go back to using 4k7 - and ponder the use of a JFET, instead of a BC547C.

Any suggestions as to a suitable JFET? I have heaps of:
* MPF102
* SJ103, and
* SK246.

And it's a perfect day, here ... but no beach time planned. :-((

Edits: 12/24/24

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