active tri line splitter using BJT transistor

[hozone]

That's perhaps a bit of a generalisation.

A designer must make the decision to include or not include caps based on their goals and intended circuit use.

For anything that is let lose on the public I would say it is mandatory to have input caps and probably output caps (which I didn't include on the above opamp diagram).

No commercial source equipment should present any DC offset at all.

Input caps are mandatory on designs using bjt opamps rather than FET because the DC source impedance has a direct effect on the offset the amp will produce (see post #11)

Remember an offset of even a couple of millivolts will produce a loud thump or bang if switched (such as input selection) and so should be avoided.

And caps aren't all bad

i'm learning...
thank you again

 

[Mooly]

That's good...

And you must try things for yourself and make your own mind up.

 

[hozone]

back to my first cricuit, i've some questions on it:

1)---
reading AMZ - Pedal Impedance i've found that the R1 resistor is a pull-down to bleed off DC from the input capacitor to eliminate audible pops, the imput impedance should be R10 parallel to R3 parallel to R1, so almost 108K
right?

2)---
i do not remeber why i've put the R2 (1k) resistor in series to C1. maybe it was for limiting the input level or for impedance match, does the impedance depens to this resistor too?

thanks

 

[Mooly]

Reading this from post #14 might help you understand better (from where it says emitter follower),
http://www.diyaudio.com/forums/anal...-optimum-bias-resistor-value.html#post2851642

R1 is in parallel with whatever the input of the emmiter follower is. Its function is pretty much as you describe. It references the input to ground and allows C1 to momentarily charge.

In practice R2 does no real harm and in scheme of things has little impact on the impedance at 1K. Its noise contribution is minimal and its effect on the HF response occurs way above the audio range.

 

[hozone]

Reading this from post #14 might help you understand better (from where it says emitter follower),
http://www.diyaudio.com/forums/anal...-optimum-bias-resistor-value.html#post2851642

R1 is in parallel with whatever the input of the emmiter follower is. Its function is pretty much as you describe. It references the input to ground and allows C1 to momentarily charge.

In practice R2 does no real harm and in scheme of things has little impact on the impedance at 1K. Its noise contribution is minimal and its effect on the HF response occurs way above the audio range.

have read all the thread, from #14 to end is very interesting, also the circuit of ribolovec2 is closer to mine.

this w.e. i will study a little more about impedance and BJT configuration.

thanks!