MXR headphone amp problems

[LiquidSteel]

Hi

I've just finished the MXR headphone amp from GeneralGuitarGadgets, but it makes a terrible distortion. I've checkt it and everythong seems to be allright. Insted of the 2n4401 I used a 2n3904 and instet the 2n4403 i used a 2n3906, could this be the problem of the terrible distortion.

I hope somebody can help me

:roll:

[niftydog]

collector current capability is significantly higher in the 4401/3 transistors than the 3904/6 transistors. Not knowing the circuit I can't say if that's important in this case or not.

[LiquidSteel]

what about a 2n5088/9 ... would they work better ??
what's comparably

[LiquidSteel]

[LiquidSteel]

can somebody help me

[niftydog]

ok, are you ready?

suitable replacements for 4401;

BC337A, BC637, BC639, 2N2221, 2N2222A, 2N5449, 2N3643, BC387, 2N5816.

for 4403;

BC327, BC638, BC640, 2N2904, 2N2907, BC307A, 2N5817.

Having said that, none of those are particularly popular. I would try 2n3904 and 3906 maybe. Failing that, you're not the first to pose this kind of question about the 4401 to the forum, a quick search might yeild some other solutions.

[LiquidSteel]

thx ... i already tried the 2n3904/6 ... perhaps the other will work ... thx

[Eric H]

collector current capability is significantly higher in the 4401/3 transistors than the 3904/6 transistors. Not knowing the circuit I can't say if that's important in this case or not.

It probably is.
The 071 has no muscle when faced with a low-impedance load (headphones)
the transistors are there to drive current, so I'm betting the 4401/3 is a medium power transistor. The 3904/6 is a small-signal transistor that will run out of steam pushing headphones. The BD139/40 comes to mind as a replacement --though I don't know if it would be a drop-in fix.

http://www.chipdocs.com/datasheets/datasheet-pdf/ON-Semiconductor/BD135.html

If all else fails, There's a real simple circuit using a NE5532 opamp (which can drive phones directly) here (scroll down):
http://www7.taosnet.com/f10/floobydust.htm

-Eric