[Q] in/out impedance

[6l6gc]

Hi, everyone!

Please let me know these circuits 'Input/Output Impedance'.
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http://www.generalguitargadgets.com/pdf/ggg_ic_buffer.pdf
http://www.generalguitargadgets.com/diagrams/buffer_jfet_sc.gif
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thanks.
&
Happy new year~

[bioroids]

Hi!

On circuit 1)(Opamp) the input impedance is the parallel result of the 3 2M2 resistors, for about 733kohms. The output impedance is very low, just the output impedance of the opamp wich can be less than 100ohms if i'm not mistaken.

On circuit 2) (Jfet) the input impedance is the parallel result of the 2M2 pull down resistor and the 2 1M biasing resistors (the FET impedance itself is much higher and will not change things), for a total of 407 kohms aprox. The output impedance, I'm sure it is low, but I dont know how much. The opamp output Z is lower, that's for sure.

Seems to be a mistake on the Jfet buffer schem, the transistor is drawn as a bipolar.

Hope this helps

Luck!

Miguel

[Sir H C]

Yeah, if the second one is really an NPN transistor you have to add the emitter resistor to the equation which is beta*( 3.3k || Rload).  So that is added in parallel with the other resistors.  Output impedance, 3.3k in effect because when the circuit is pulling the output down, that can only happen through the 3.3k resistor.  Pulling up the output impedance is lower but requires more details about the transistor to really give a value.

[6l6gc]

thanks very much guys

Can I those circuits...substitute for D.I Box? (Guitar equiped with passive pups -> Audio card:10K ohm input)

[bioroids]

Yeah, I think that can work.

I use AMZ Mosfet Booster for that, that way I can raise the volume besides adapting the impedance.

Miguel

[6l6gc]

Oh, that's good idea!
Where can I find "AMZ Mosfet Booster schematic,pcb layout,wiring layout" ?

[bioroids]

http://www.muzique.com you should look around there for the schem. I dont know if there's a pcb somewhere, maybe on general guitar gadgets, or tonepad.

Luck

Miguel

[6l6gc]

thanks, bioroids!

AMZ PROJECT is in GGG & tonpad.

thanks