SOLVED Phase 90 vero with script switch lfo thumping when switch is enabled, only at slower rates

[Locrian99]

Ok so this is starting to make me lose my mind. This was one of my first 5 builds. And awhile after I built it I noticed this and I’m assuming it always did it and I just never had it set for it. Basically if the switch is enabled probably the final 70% of the rate knob it doesn’t do it below though you get a thump with the lfo. At lower rates you can tell that it’s not one thump but several in succession. It does not do this with the switch not enabled. I’ve reflowed the switch solder connections etc. I’ve audio probed it and the thumping shows up at pin 1 of the tl072 at the top. The jfets I’m using are 5457’s all matched to within a 10mv range. I changed the 3m9 resistor (I built this in July so im trying to remember any mods I might have made) to 3m3 if I remember correctly sounded better. I removed the board from the enclosure because I was thinking it might be touching something in there as it’s kind of free floating. And nope still does it.
Just not sure where to look to fix this at this point hoping someone has a suggestion.

 

[fig]

Does the DEPTH knob effect (soften) the thump?

Edit: The R24 3m9Ω ties the rate and last stage of IC3 to the rest of the circuit. Do you recall the thump before modding it?

 

[Locrian99]

Does the DEPTH knob effect (soften) the thump?

Edit: The R24 3m9Ω ties the rate and last stage of IC3 to the rest of the circuit. Do you recall the thump before modding it?

I’ll have to check the depth I haven’t hadn’t really messed with that. No I don’t recall it before that change (doesn’t mean it wasn’t there). I can certainly try putting that back to the 3.9 though. I prefer the switch off, so I pretty much left it off. About a month after boxing it I was playing and decided to switch over to the other setting. Big thump and there it was. After I get the kids to bed I’ll play around with the depth, and swap that back to a 3m9

 

[music6000]

Ok so this is starting to make me lose my mind. This was one of my first 5 builds. And awhile after I built it I noticed this and I’m assuming it always did it and I just never had it set for it. Basically if the switch is enabled probably the final 70% of the rate knob it doesn’t do it below though you get a thump with the lfo. At lower rates you can tell that it’s not one thump but several in succession. It does not do this with the switch not enabled. I’ve reflowed the switch solder connections etc. I’ve audio probed it and the thumping shows up at pin 1 of the tl072 at the top. The jfets I’m using are 5457’s all matched to within a 10mv range. I changed the 3m9 resistor (I built this in July so im trying to remember any mods I might have made) to 3m3 if I remember correctly sounded better. I removed the board from the enclosure because I was thinking it might be touching something in there as it’s kind of free floating. And nope still does it.
Just not sure where to look to fix this at this point hoping someone has a suggestion.View attachment 35442
View attachment 35443

I'm curious why you didn't build this:

XC Phase - PedalPCB.com

Compare to MXR Phase 90

www.pedalpcb.com

 

[Locrian99]

I'm curious why you didn't build this:

XC Phase - PedalPCB.com

Compare to MXR Phase 90

www.pedalpcb.com

Well I was mainly building on Vero at the time I built this, it was 3-4 months ago. I like building on strip board for certain things. Still do sometimes if it’s small enough and I can comfortably fit it into a 125b still without the wiring being to nutty. I’d probably build this on a board if I was to do it today just because I’ve realized spending 3 hours to build a board on vero isn’t worth saving the 12 bucks. Just depends on the build though which way I’d go.

 

[Locrian99]

Does the DEPTH knob effect (soften) the thump?

Edit: The R24 3m9Ω ties the rate and last stage of IC3 to the rest of the circuit. Do you recall the thump before modding it?

So the depth knob does affect it. Not in the way I expected it to though. So the lower the depth knob is set the higher the rate knob can be and still so it. Depth at the lowest setting it does it the full range of the rate knob and as you move the depth up you get a little more rate knob that doesn’t do it.

 

[Locrian99]

Well changing the resistor didn’t fix it. I was however able to get it to stop by changing the bias trim. But it sounds like it’s clipping more now than it was where it was doing it. Guess I need to play with that some more. It’s a slight clipping but I can hear it.

 

[Locrian99]

Well I’ve spent the last 2 hours messing with the trimmer and swapping out that 3m9 and 3m3. Ran wires to a breadboard. I can’t seem to decide where it sounds best. Lol. But it’s working fine now I just need to make a decision and stop being so picky. Of note one of the leading spots for bias location is right basically where that thumping stops, which makes me wonder if that’s where I had to to and somehow it got nudged. Haven’t played wirb the trimmer since I boxed it up.