43 thoughts on “John Hollis’ Ultra Flanger

  1. The regen pot should connect to ground according to the original schematic…

  2. I am still fighting this one, built using the Geofex layout. I replaced the 2 leds and diode with a 3.9 volt zener but the voltage was too low. To check the zener was OK, I breadboarded just the zener and the 10k resistor and still did not get 3.9 volts. I then replaced the 10k resistor with a potentiometer and turned it down until I got the correct voltage. The resistance was around 1.3k! I also tried a couple of other zeners with different values and they behaved the same way. From what I Googled, zeners require a minimum current before they operate. Could this be the problem?

    I am still experiencing another problem. The voltage to the final stage op amp is about 0.6 volts too low. I am getting distortion. Otherwise it is working.

  3. Hi there, like most of the readers here, I’m unlucky. It doesn’t work at all. I deeply think this stripboard IS NOT VERIFIED.

  4. Sorry to hear that, Peter. From looking at the comments you might be right saying it goes nowhere, and the layout says it’s verified, but I can’t see I wrote down who it was (maybe it was me?). As a general comment I’d say flangers are some of the hardest effects to get right, and this could be considered a very challenging build.
    Have you checked out the forums (links on right-hand side) for general info on the Ultra Flanger? Short of taking the time and resources off to building this myself just for testing there’s not much more I can do, sorry 🙁

  5. Hi Guys,
    I have been at it for about 4 weeks now, still no joy, it also appears this thread is going nowhere, is there more info on this flanger, I purchased all the items on the basis that it was verified, has anyone built it as per the vero layout and got it working if so was anything changed parts wise, It would be nice to hear from some one who has some answers.


  6. Hi everyone, I am having a problem with ultra Flanger .
    the voltage at the junction of r8, pin6 (ic1) and the 3.9 zener, I assume it is ment to be around 3.9v, but I am only getting 2.300v,
    in the past few weeks I have checked the board for errors, all components are in there correct place and are the correct values, the ic’s have been replaced, all looks correct and has also been checked by a couple of other friends, just to make sure,

    Can someone please help me out.

    Regards Peter

  7. I have to disappoint you and tell you I have no experience with this effect, but given it’s a flanger there’s definitely some sensitive parts to this effect that might require some debugging.
    Given that it’s hum, have you tried swapping in a battery for the usual power supply? If the hum disappears with the battery but returns as you plug in your power supply, you can be reasonably sure it’s noise coming in via the DC jack. From there on, check power filter caps etc. Just a thought.

  8. Hi Harald.
    I put this together and mistakenly put a tl072 in the mn3007 place. I switched it out and put all ‘new’ chips in. I hear the effect but there is a loud hum (70/30, hum to effect)over the output. I checked everything and all seems correct. Do you have a thought as to what causes this hum? Did I burn something with the 72 misplaced? Thanks for the builds.

  9. Thank you Harald, I found the answer for led with true bypass. I have another problem now. The effect is weak in the sound of the guitar, which barely seems to have little flanger the sound. I set the trimmer in different areas, but nothing different.

  10. Hi Pete,
    If you mean the normal “on/off” LED you place it according to the off-board wiring scheme (typically regular true-bypass). Check out the “wiring” section for diagrams.

  11. Jeff, your best bet may be to string together several diodes in series for an added voltage drop close to what you need. Off the top of my head, generic small-signal diodes like 1N914 and 1N4148 have a voltage drop of ~0.6V; 6 of those would do it, but that’s a bit impractical.

  12. Jeff, it means the when the switch is in first position (connecting pins #1 and #2) you get the “odd” setting, and the opposite (connecting pins #2 and #3) you get the “even” setting. Now, what exactly “odd” and “even” entails I’m not sure of.

  13. I’m not sure about the buffered vs. unbuffered for this specific project, but generally it seems the unbuffered version is the one to use.

  14. Is there anything I can do to use a 3.6v or higher (I have no 3.9’s) diode for #1?
    Could a resistor be changed in series with d1 to use a diff v value diode?

  15. I hope I’m not writing to the ether here but what does ‘Odd/even SW 1-2:Odd’ mean?
    Also ‘Odd even SW 2-3: Even’.

  16. Hi all.
    I want to build this but am unsure about the 4049 chip. I remember seeing that the ‘U’ designation means unbuffered. I have several 4049UBE chips. Will they be ok to use in this?

  17. Just a thought, but perhaps the bias voltage is the issue here? Could try replacing R21 and R22 with a single 25k trim pot.

  18. Depending on the value of the pot you have in series with 9v you may need to try very slight turns to get it to flange.

  19. vr1 and vr2 work with the odd/even switch, vr1 is in circuit with the switch set 1 way, vr2 with it set the other way. The trimmers are for setting max regen, so ideally you want to turn your regen pot to max (if I remember correctly this is backward and max regen is anti clockwise, unless I messed up :-)) set the trimmer till you get self oscillation then turn it back to the point where it just stops, flick the odd even switch and do the same with the other trimmer.

  20. Sounds like a flager but only noise, like white noise. I don’t hear the guitar. With 9V there is clean signal but no flanger.
    Trimmer VR1 does nothing, only VR2.

  21. try 2k or 5k (10k at push) pot in series with the 9v supply, see if you get flanging as the voltage decreases.

  22. Revisited this today and ended up building another one, same result, signal but no flanging. While debugging I started messing with the sag pot on my power supply (ala beavis I/O box) and it started to flange. Tried it with my original build and it was the same. Upshot is that this circuit appears to be not overly keen on 9v, From 9v down to 8v it goes from dry signal to a pseudo reverb type signal. below 8v to around 7.4v it flanges, below 7.4v it distorts. This was the case with both builds, both also have ticking issues which I will try to address tomorrow, will let you know how I get on.

  23. I’d like to build a version of this without the LFO. I just want to use the ‘manual’ and operate it with a wah pedal. I’m having a hard time matching your vero layout to the schematic I have. What parts of your vero would I leave out to skip the LFO?

  24. Sorry to hear that, Derek. The original schematic says nothing about using any specific type of the ICs, so I assume both versions will be fine. I haven’t built this circuit myself so there’s very little advice I can give you other than the stuff I’ve written in the debugging section. Hope you figure it out.

  25. Built this tonight, I’m getting dry signal through and it flanges if I manually turn the sweep pot, I’m using a cd4049ube (unbuffered) does this need the be ( buffered version?

  26. I’m not sure. Have you looked at the datasheets? Probably wouldn’t hurt to try, but I’m guessing you don’t have both.

  27. I’m unsure actually. I haven’t attempted this myself, but I seem to recall someone giving it a try and had some ticking issues. That doesn’t necessarily mean the layout is at fault, though. I’d be very interested in knowing how it ends up if you finish this circuit.

  28. You’re right, on the Hollis’ schematic it’s goes to Vref, I didn’t notice. So it should work alright. But as I said because the layout wasn’t verified I compared it to the Geofex version and it said ground so I went with ground from the beginning.
    If anyone was interested it is really easy to adapt the geofex mods into this layout, there’s enough place for the components.

  29. Nice, lopsided!
    I did the layout based on rev. 3 of the handwritten schematic off Hollis’ own site. I double checked and the schematic says regen connects to vref and not ground. That may of course be a mistake. Did it work either way or just when connected to ground?

  30. I have build the Ultra Flanger from your layout. Not sure, which schematic did you use. I have used the one at Geofex as a reference. I think the layout incorporates some of GEO mods and some not, but none of them are crucial I believe. The only possible mistake I have found is that Regen 3 should go to ground not to to the 4,9 Vref as on the layout {maybe it would work anyway, I don’t know}.

    I really like the flanging it does. Unfortunately, while my Zombie Chorus build was tick-free this one is ticking as hell and makes it almost unusable for recording or live. Will try some other mods for deticking and see if I make it work.

    Thanks a lot for the layout! Probably wouldn’t be able to build it without.

  31. I might one day, but right now I’ve got plenty of other projects to keep me occupied for the time being, sorry. If you feel like trying it do let me know if you make it work.

  32. I just played briefly with the circuit last night and my first impression was a distortion effect with a broad range of sounds, albeit a little sterile sounding. Based on my limited tweaking of the various controls I found it more aggressive and edgy than smooth or mellow. Going to experiment more with it once I find a box for it.

  33. How do you like the Omnidrive? Seems like a great tweakable overdrive. I’m curious about the pros and cons of it. I’ve read forum threads where some say it’s excellent, as well as some saying mediocre at best.

Leave a Reply

Your email address will not be published. Required fields are marked *

Time limit is exhausted. Please reload CAPTCHA.