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Hey guys, Barry, everyone – just curious if anyone else had any weird issues with getting the DLay to fully Oscillate – I’m almost certain I just have some slight mathematical issue holding me back somewhere as far as the trimmer/RA settings go. I’ve built almost 60 of these and every now and then I get a weird Feedback/Repeats pot issue with it just wanting to fade out or be right on the verge of Oscillation/Infinity. Normally I run a B50k pot on Repeats, 5k Trimmer, and 3.9k resistor to get perfect oscillation capability. I went ahead and removed the RA and put in a socket. I have it working, but it just will not oscillate with any resistors I put in. I may just need to create the perfect mathematical resistor solution. So far, I have heard the same near oscillation but not fully with 1k-3.9k, 4.7k, 5.8k, and so on.
Let me take some pictures of my build, and double check any substitute parts I may have used. Otherwise it sounds great and gets some good repeats – just not the fully oscillating stuff I love. Tried new chips, voltage regulator (socketed parts) and it still did the same thing.
I noticed that it did oscillate as normal without the 072 chip in the socket. (But ofcourse would not carry a signal) But the oscillation happened and the knob controlled it.
I’m about to build another one up identical parts etc. next to it, I’ll see if it does the same thing.
The problem is most likely due to high tolerance components. AKA acceptable margin of error.
Up to 20% on potentiometers, trimmers and capacitors.
Better capacitors can be 5-10% off and still acceptable. 20% is typical with potentiometers especially with the types we as DIY enthusiasts commonly use, many which are labeled but are knock-offs.
Those differences when combining more than one component (potentiometer, trimmer & capacitor) are going to add up creating a scenario where you will have to experiment with the final resistor value to achieve the desired effect.
Additionally you are supposed to use a C50K Pot. The anti-log taper potentiometer is used to ensure that controls have linear characteristics as perceived by the human ear. (This is not as important as tolerance).
Also try testing your components before installing them or vary the key resistor etc to get what you need.
A final possibility could be just a simple build error. Both of us have built many and I can only speak for myself when I say I still make errors.
+1 Barry.
Gee, I thought I could contribute more to this thread. But, when I reread Barry’s comments I think he has hit the nail on the head. Component tolerances and active component responses have a great deal to with the final response.
I would always suggest building the circuit to stock values first to ensure that it works as advertised. Then try mods one at a time to tweak the pedal.
With your experience with this circuit, you have obviously proven this to be true before. I’ll bet a cold Coors Light beer that the next one you build will perform differently!
btw THANK YOU!! Wilkie and Barry, I was absolutely certain I had something wrong on my end – you guys were there so fast to help, please mark as FIXED!!
Thanks, Wilkie! I usually don’t do more than 1 or 2 PCBs at a time, and lately I’ve been doing more batch related work – so this was sortof one of those ‘slow down and take your time and get things right’ lessons in life.
Cheers!!
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