Input impedance resistor, F4 amplifier

[Manolo47]

Is the quality of this input impedance resistor that important for the quality of sound? I am asking this question because I need to bring the input impedance fron 47500 ohms to around 41,000 so i can use a given cap in my HP line filter. I am considering installing a 300,000 ohm resistor from line to ground in the preamp's output which would give, with the F4's impedance an
effective impedance of 41,000 ohms. So, I only have Xicon metal films for this and was wondeing if this choice would affect the sound quality.
Thank you all.

 

[Zen Mod]

just go for it

 

[d to the g]

thinking about an 1:4 input transformer for some gain... just how low can we go with the input impedance?

 

[Zen Mod]

as much source can manage without loosing steam

so - what's output impedance of previous gadget ?

 

[d to the g]

that would require some sort of stereo stasis! I have a couple of different buffer preamps B1, not quite finished heretical, but things seem to be constantly changing.

The LL1545A datasheet recommends a "real source impedance" of 37 ohm, but the amplifier side would only be 10K. I guess it's a matter of whether the F4 will like it?

 

[Zen Mod]

F4 doesn't know what is feeding it with signal ;

little Jfets doesn't know what value of resistor is from their gates to gnd

what you need to think is proper value of net needed to linearize xformer ( net means either solo resistor or resistor in series with cap , across secondary )

so - just leave F4 as is , thinking only of needed voltage to feed it .

also - think about using xformer in autoformer mode - that way you'll have slightly improved sound

 

[d to the g]

also - think about using xformer in autoformer mode - that way you'll have slightly improved sound

sounds like something that can easily be tried both ways.

 

[Zen Mod]

exactly 😉