The 78L05 ground pin shouldn't actually be attached directly to ground; it should be attached to ground via the 1N914 diode. It's a trick Madbean uses to boost the performance of the PT2399 by running it a little above 5v, which is barely in spec. You'll have to scooch the link between 5-K and 5-O over to column 8, perhaps, and then cut the trace at 5-O. Something like that. Or just remove the 1N914 and run the PT2399 at 5v.
I built this and it works well. Having the internal trimmer for feedback is a really nice feature ... you can get a lot more useful range out of the feedback pot.
Still, I'm having a helluva time with my DIY LED/LDR combo for the bloom feature, and that's really the claim to fame of this device. The LED just isn't getting bright enough to interact with the LDR. I ended up replacing the 100K resistor with a 100K trim pot and even at zero it's just not enough. I'm going to mess around with different LED's or maybe add more gain to the LM386 by adding a cap across pins 1 and 8. It will eventually work. I should have sprung for an actual NSL32R vactrol but I was too cheap.
The LDRs out there with the widest swing that I can find are NSL-19M51. They are about $0.90 each and have 5k/20m light/dark resistance. That and a superbright white LED might do the trick.
Hey all - I gave this one a shot today and encountered the same issues as Michael. Everything works as it should except for the "bloom" control, which is the envelope-controlled modulation driven by the vactrol and the LM386 amp. I tried the correct vactrol, as well as a couple of LED/LDR combos with a really wide on/off resistance swing. I lowered the value of the 100k resistor feeding the LED half of the vactrol as well - and still, no modulation at all. I stared at the Madbean schematic and the above drawing for a while trying to find any discrepancies, and other than a few minor modifications to the power supply, I couldn't find anything.
There is only one demo video of this circuit on youtube but the wobble is pretty noticeable and extreme. Without it, this is just a typical sounding PT2399 delay. So I'm giving up on this one, for now.
Although the link in the above post is still active, Madbean has the Degenerator listed in their "coming soon" section, as a 2024 updated circuit and PCB is about to be released. I'm going to get that schematic as soon as it is available because I'm quite eager to see what changes were made.
The 78L05 ground pin shouldn't actually be attached directly to ground; it should be attached to ground via the 1N914 diode. It's a trick Madbean uses to boost the performance of the PT2399 by running it a little above 5v, which is barely in spec. You'll have to scooch the link between 5-K and 5-O over to column 8, perhaps, and then cut the trace at 5-O. Something like that. Or just remove the 1N914 and run the PT2399 at 5v.
ReplyDeleteHmmm, no, column 8 isn't free. Maybe a double-link at 6-O and use column 6? You're way better at this than I am.
DeleteThanks for noticing this, Michael.
DeleteThe layout is updated.
I built this and it works well. Having the internal trimmer for feedback is a really nice feature ... you can get a lot more useful range out of the feedback pot.
ReplyDeleteStill, I'm having a helluva time with my DIY LED/LDR combo for the bloom feature, and that's really the claim to fame of this device. The LED just isn't getting bright enough to interact with the LDR. I ended up replacing the 100K resistor with a 100K trim pot and even at zero it's just not enough. I'm going to mess around with different LED's or maybe add more gain to the LM386 by adding a cap across pins 1 and 8. It will eventually work. I should have sprung for an actual NSL32R vactrol but I was too cheap.
The LDRs out there with the widest swing that I can find are NSL-19M51. They are about $0.90 each and have 5k/20m light/dark resistance. That and a superbright white LED might do the trick.
DeleteHey all - I gave this one a shot today and encountered the same issues as Michael. Everything works as it should except for the "bloom" control, which is the envelope-controlled modulation driven by the vactrol and the LM386 amp. I tried the correct vactrol, as well as a couple of LED/LDR combos with a really wide on/off resistance swing. I lowered the value of the 100k resistor feeding the LED half of the vactrol as well - and still, no modulation at all. I stared at the Madbean schematic and the above drawing for a while trying to find any discrepancies, and other than a few minor modifications to the power supply, I couldn't find anything.
ReplyDeleteThere is only one demo video of this circuit on youtube but the wobble is pretty noticeable and extreme. Without it, this is just a typical sounding PT2399 delay. So I'm giving up on this one, for now.
Although the link in the above post is still active, Madbean has the Degenerator listed in their "coming soon" section, as a 2024 updated circuit and PCB is about to be released. I'm going to get that schematic as soon as it is available because I'm quite eager to see what changes were made.