XC Phase transistor orientation

sticky1138

Well-known member
I built the XC Phase and it does a phased sound, but it's "fixed" and doesn't modulate, despite my attempts at biasing.

I have the revision 2 board and I'm using a matched 2N5952 set from GPCB. I'm thinking maybe they are installed backwards, even though they match the orientation depicted on the silkscreen. I'm still a bit confused, maybe I'm missing something.

Here's a shot of my PCB:

CblO1SQ.jpg
 
If those 2N5952's then the orientation is correct. I'd try the trimmer again, those open style trimmers don't have the best resolution. Real super small moves. It's a tiny range where the phasing is the strongest. If you are getting filtering but no whoosh then you're pretty close.
 
I’m gonna say it’s the LFO and not the trannies. What do your voltages look like?
I second this....

If those 2N5952's then the orientation is correct. I'd try the trimmer again, those open style trimmers don't have the best resolution. Real super small moves. It's a tiny range where the phasing is the strongest. If you are getting filtering but no whoosh then you're pretty close.
...and this.
 
I’m gonna say it’s the LFO and not the trannies. What do your voltages look like?

Not too familiar with how an LFO works. Are you referring to the voltages on each IC pin? What can I reference to see what those values should be?

If those 2N5952's then the orientation is correct. I'd try the trimmer again, those open style trimmers don't have the best resolution. Real super small moves. It's a tiny range where the phasing is the strongest. If you are getting filtering but no whoosh then you're pretty close.

I didn't realize the "open" trimpot and 3362 type respond differently. Would you recommend keeping the same value if I swapped it out? And would that make it easier to find the "spot"? I feel like I've adjusted in the tiniest increments possible by human hand.

Now that I think about it, I also used this type of trim on a chorus I built long ago and was never able to perfectly bias without distortion. Maybe that's the same problem there as well.
 
Not too familiar with how an LFO works. Are you referring to the voltages on each IC pin? What can I reference to see what those values should be?



I didn't realize the "open" trimpot and 3362 type respond differently. Would you recommend keeping the same value if I swapped it out? And would that make it easier to find the "spot"? I feel like I've adjusted in the tiniest increments possible by human hand.

Now that I think about it, I also used this type of trim on a chorus I built long ago and was never able to perfectly bias without distortion. Maybe that's the same problem there as well.
The voltages on your JFets should be fluctuating, sorry about that.
 
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