Help me understand my Phase 90, Please. Why does it sound different....

[jimmybjj]

.....then my factory block unit. I used the schematic from tonepad. When playing them side by side I notice a couple of things. The speed on the factory unit is a lot faster, this doesn't bother me because i don't ever intend on using it in the extreme settings. Second, the factory unit seems to accent upper frequencies when phasing and the my unit seems to accent more upper-mids at the end of its sweep. To me the factory units sound is more pleasing (aside from the intensity) Is this because the pedals have different sweeps and I'm perceiving them to sound different or are they really accenting different frequencies? How would anyone suggest i start changing mine to sound more like the factory. Last question, I'm still learning and trying to understand the different segments of circuits, is the q5 a output buffer? Would changing this transistor from 2n3906 to the 2n4125 make any sonic differences? Thanks for any help.

[R.G.]

How do the schematics compare? Same circuit? Same part values?

That's the place to start.

In general, changing from one part number of transistor to another makes a vanishing small difference in most circuits. There are exceptions, but they are unusual.

[Mark Hammer]

1) The bias trimpot plays a role in not only enabling sweep (by providing a basic DC voltage to the FET gates), but also a role in situating the range of that sweep.  You can tweak that bias trimpot and move the range a little higher...or lower.  Quite likely that your two units could have identical-sounding sweeps with the adjustment of their respective bias trimpots.

2) Often, changes in parts (like transistor) can play a smaller role than tolerances (and inter-component variation) in what's already there.