[sdiy] DOD FX20 & 4558 mojo

[anthony]

I got a broken FX20B phaser at a music store here for $5.00 I've already 
fixed it, but I want to increase the low-end and maybe make some other mods.

I have to say I was impressed to discover that this phaser was a 6-stage 
unit using 3 LM13600's. I figured most stomper phasers were only 4, maybe 5 
(isn't the small stone 5?).

I dunno why i can't find a schematic for it. I have one for a lot of the 
other FX-series pedals.

Actually I really like the way it sounds. I changed the LF353 for a 
JRC4558DD and now it distorts a little better when overloaded. So I really 
like it now. (I've really come to the conclusion that unless you need a 
really high input impedence, bipolar op-amps are the way to go instead of 
BiFET amps. It could be the 4558 itself. I have more of these than any other 
op-amp and I've never gone wrong with them. There's talk of the old make 
JRC4558D's having some special mojo and I have observed this, but the 
JRC4558DD has even more mojo (it's lower noise too). I'm happy that I have 
more DD's by far. I also have some TI and NEC 4558's - both very good. I 
think these good qualities probably extend out to the whol 45XX family. I 
have 4570's and 4574's (dual and quad resp of basically the same op-amp). I 
wish the 4570's I had weren't SIL's - I'd like to drop them in places where 
I'm using 4558's to compare. I find that the M5218 is a good op-amp too.