Phase 90 R28, R31, C11 and C12

[sircletus]

I know that R28 on the Phase 90 is the feedback resistor, but which resistor is R31, and which caps are C11 and C12?  Are there any schematics out there with the component numbering?

Thanks,
SirC

[iaresee]

No schematic for you sorry, but when I did my Phase 90 mods I used the Erik's Corner article. He's got a picture of a Phase 90 reissue board with R28 and C12 pointed out if that helps: http://www.erikhansen.net/diy/phase90scriptmod.jpg

[mdh]

Can't vouch for it, but there was a guy who was really into modding Phase 90s that came up with a numbered schem and put it in the layouts gallery here.

[sircletus]

That's a very interesting numbered schematic.  Thanks so much!  It's interesting, though, I've already made some of those modifications just by playing around with values of caps and resistors.

Thanks again,
SirC

[George Giblet]

R28 is the main change, it adds feedback which changes the sound/behaviour of the unit.

In theory R31, R32, C11, and C12 should not change the tone.  These components form a pre-emphasis/de-emphasis network which aims to reduce noise without affecting the overall frequency response of the pedal.  The same idea is used in most delay pedals and the Boss EQ pedal (and others).  I haven't analysed how well the pre-emphasis and de-emphasis match up.