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Need help with JFET preamp and chossing transistor ? Answered

Hello .I'm having some some problems with my current project .Can you guys help me please !

This is the schematic of MXR headphone amp for guitar .I don't have 2n4401 and 2n4403 , so i replace them with 2n3904 and 2n3906.The result is output is too low .2n4401 and 2n4403 (collector current = 600mA) ,2n3904 and 2n3906 (collector current = 200mA).If i replace the transistor with higher Ic i will have louder output ???

Thanks for advance!
Sorry for my bad English!


Ok, for your JFET preamp, you should change the value of of the input cap to 0.1 uf and the bypass caps (at the 1.2k resistors) should be increased in value as well, experiment with them to find the desired tone.

For the headphone amp, a quick way to increase the level is to:
A.) Increase the value of R9 (less bleed off to ground), use a potentiometer to find a good value.
B.) Reduce the value of R10/11 (allows more current through), same method as above.

Let us know how your projects turn out.