Hi! I breadboarded this based on (apparently) the same schematic that You've used to make the layout. The problem is that it's more like an overdrive than a distortion. I found a mod suggestion that implemented a 100k gain pot instead of the fixed 120k resistor between pins 6&7 of IC1. That didn't do anything, the sound is still the same. Actually, the sound doesn't change if I remove the 120k altogether (or up the resistance up to 1M). What's going on? How can I make this thing SCREAM? :D
Yeah, the output buffer don't affect the gain the circuit. Are you sure you have a 220k resistor across pin 1 and 2 of IC1? That resistor sets the gain of the first stage. It could be something wrong around theyour gain pot since it is working. Mine screams and howls for sure!
Yeah, the 220k is there. Since this one is verified I might as well build it on stripboard, there's no point in wondering it further. The reason I built this on breadboard was that I didn't find any stripboard versions...until I had the thing rigged and trying to troubleshoot it :D Thanks anyway!
I'm getting a ton of weird oscillation. The earliest in the circuit I'm finding it is the Source pin of the JFET. I've tried everything I can think of and can't find any feedback loops are busted components but I'm still relatively new at this. I'm building it for a friend who's really excited about it. Any tips on how to fix it?
I decided to do the whole layout again. This time no oscillation, but it's extremely gated and crackly. With a signal probe I have nothing coming from the left side of IC1, but it's coming from the jfet just fine. I've replaced the 100pf and 47 nf caps nearby with no luck. I've built plenty of pedals, many bigger than this, so I don't think its my soldering. What's going on?
Sorry, missed your earlier post. Which J FET are you using? Bear in mind that 2sk30 have a different pinout than most western world J FETs like J201, 2N5457 etc. Not sure what the issue could be. As you wrote, something is wrong at the first op amp...
I've tried j201 and 2n5457, both with the pins twisted to be in the correct slot. Turns out the second one was a dumb mistake made by a tired brain and now it sounds great! I still can't figure out the oscillations though. I've compared my first board to the second and taken readings all over. They look and read identical. I've tried different opamps and even transistors in Q2. No luck so far. Thanks for the layout(s, the hundreds of beautiful layouts) though!
Yeah, it is apretty noisy circuit as is and probably even noiser on stripboard. Have you tried it with a buffer up front? Here is a small demo showing some noise issues this thing cn suffer from... https://youtu.be/7dVZduDRbSI
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ReplyDeleteFX86 :)
ReplyDeleteThanks!:-) Updated the layout.
DeleteHi! I breadboarded this based on (apparently) the same schematic that You've used to make the layout. The problem is that it's more like an overdrive than a distortion. I found a mod suggestion that implemented a 100k gain pot instead of the fixed 120k resistor between pins 6&7 of IC1. That didn't do anything, the sound is still the same. Actually, the sound doesn't change if I remove the 120k altogether (or up the resistance up to 1M). What's going on? How can I make this thing SCREAM? :D
ReplyDeleteOh yeah, I did NOT omit the output buffer stage after Level pot. But I don't think omitting it would help in this matter?
DeleteYeah, the output buffer don't affect the gain the circuit. Are you sure you have a 220k resistor across pin 1 and 2 of IC1? That resistor sets the gain of the first stage. It could be something wrong around theyour gain pot since it is working. Mine screams and howls for sure!
DeleteYeah, the 220k is there. Since this one is verified I might as well build it on stripboard, there's no point in wondering it further. The reason I built this on breadboard was that I didn't find any stripboard versions...until I had the thing rigged and trying to troubleshoot it :D Thanks anyway!
ReplyDeleteLet us to know if you built this layout, too. ;)
DeleteI'm getting a ton of weird oscillation. The earliest in the circuit I'm finding it is the Source pin of the JFET. I've tried everything I can think of and can't find any feedback loops are busted components but I'm still relatively new at this. I'm building it for a friend who's really excited about it. Any tips on how to fix it?
ReplyDeleteI decided to do the whole layout again. This time no oscillation, but it's extremely gated and crackly. With a signal probe I have nothing coming from the left side of IC1, but it's coming from the jfet just fine. I've replaced the 100pf and 47 nf caps nearby with no luck. I've built plenty of pedals, many bigger than this, so I don't think its my soldering. What's going on?
DeleteSorry, missed your earlier post. Which J FET are you using? Bear in mind that 2sk30 have a different pinout than most western world J FETs like J201, 2N5457 etc.
DeleteNot sure what the issue could be. As you wrote, something is wrong at the first op amp...
I've tried j201 and 2n5457, both with the pins twisted to be in the correct slot. Turns out the second one was a dumb mistake made by a tired brain and now it sounds great! I still can't figure out the oscillations though. I've compared my first board to the second and taken readings all over. They look and read identical. I've tried different opamps and even transistors in Q2. No luck so far. Thanks for the layout(s, the hundreds of beautiful layouts) though!
DeleteYeah, it is apretty noisy circuit as is and probably even noiser on stripboard. Have you tried it with a buffer up front?
DeleteHere is a small demo showing some noise issues this thing cn suffer from...
https://youtu.be/7dVZduDRbSI
Plan to build this one sure. Dod fx86 is something worth building for!
ReplyDeleteThe circuit itself is awesome. !
Verified!! Sounds awesome metal!
ReplyDelete