A transatralntic trace by Enrico, AlexS and fuzzhead.
A big thanks goes to Enrico for letting us trace his pedal, all the images and the schematic.
The layout is tested and verified. There is some odd parts in there which can easily be subbed for other values. (221ohm to 220 ohm and 4,64k to 4,7k). MPSA05G transistors isn't that common but MPSA06 which is more widely avaiable works fine and is almost identical spec wise.
Also, Overload is linear, not log as in the first posted layout.
Awesome!! Thanks all three for making it available for DIY'ers. Now we're only missing Waveform Destroyer:D
ReplyDeleteYeah, and a bunch of custom stuff.:-)
DeleteRight!! saw the limited Exit Index and Pinned fuzz pop locally, had half of mind to buy 'em to trace 'em. Alas, they were sold.
ReplyDeleteI was curious about the Exit Index too.
DeleteHey Guys, built this up today and it works but it's nowhere near the production model. It gets a little bit crazy but nothing like the original.
ReplyDeleteHaving no MPSA05Gs, I tried 2N3904s as per the notes. Only have LM386N-1. Would having a 386D make any difference?
It seems like it need way more gain or something.
Also Gain pots need to be reversed. All else is sweet. Cheers for the layout!
Hi there. Ok, 2N3904 might not work as good as I stated. Those reverse beta gain stages can be very sensitive to which transistors you are using. I was using MPSA06 which is widely avaiable in my area and I has plenty of gain on tap. I was using LM386-1 so the power amp don't seems to be the culprit.
DeleteAre you sure about the gain pot being reversed? Mine works as with more gain clockwise. The Overload control needs to be reversed, indeed. I'll fix it.
Thanks for the reply fuzzhead! I'll try a few more different transistors while I wait for some MPSA06 to come in. I'll have to check the gain pot again. I may have just wired it the wrong way and not realised. Cheers!
DeleteGain is the right way round, it was the Overload control that I was meaning.
DeleteI've tried a pair of BC548s and it now seems a lot closer to the original.
I did neglect to mention that I'm using 4.7v Zeners as that's the closest I had. Just tested it again and it seems the gain pot is doing nothing. There's plenty of gain but the pot has no effect on its level. Weird!
I have a switch between pins 1 & 8 of the 386, I'll remove it and see if that makes a difference before changing the pot.
Ok, it seems that the BC548s had too much gain, negating the gain pot(even if that's possible, haha). Tried some 5089s(just over 500Hfe, I think) and they are perfect! Gain pot works nicely. Also tried a pair of BC109s and they were a little low, giving a dull sounding tone at min gain.
DeleteThe only thing I'm not getting is the octave up tone at 12 on the Overload control. I'm guessing that's due to the 4.7v Z in D1 & D2.
I'm always happy to see more DBA layouts, it's my favorite pedal company for sure! And this website is quickly becoming my favorite, so thanks a bunch Fuzzhead!
ReplyDeleteI just built it with MPSA06G, LM386 and all linear pots. There is a low droning noise when gain is set anywhere other than minimum. Sounds like lower octave-ish noise that occurs when my big muff clone feeds back to itself. I'm not sure if it's a quirk of the pedal or my sloppy build. Can anyone tell me if this happens in their builds? I get the "blooming" effect with the overload pot, it's pretty unique and nice but that low noise drives me crazy!
Hi there! Thanks for your kind words.
DeleteIt seems that you have a build error somewhere, sounds as you wrote, a feedback issue. Have you knifed the gaps and cuts, triple checked everything, checked solder joints etc. ?
Does the noise change frequencies when turning any of the pots?
Do you get octave up with the Overload pot at noon?
thanks for the quick reply! I knifed the gaps, tried some new pots with crocodile cables but to no luck. Somehow when I replaced the battery, the issue was solved. Weird. maybe I accidentally moved a croc cable to a better connection.
Deletebut now, I don't get the swell effect with both knobs at max. it just gets octave up-ish like the original pedal gets around noon but no crazy glitching effects even when it's full. that's also weird :D
oh, the overload pot isn't backwards. I saved the image the day it was posted so I used that as a reference. I guess that should be the issue, but why it occured after my first problem was solved is still a mystery to me :D
DeleteNope, didn't help :( any idea why?
DeleteTry a differnt Lm386 and/or higher gain transistors like 2N5088?
DeleteJust finished mine and it works great. Like most DBA stuff, it’s very sensitive to which Transistors you use. I tried many and ended up with a pair of 2n5088s around 380hfe. For fun, try reversing one or both the trannies for crazy bonus sounds. I also used an lm386. My 1mb gain pot jumps hard from 0 to 2, then nothing from 2 to 10. A different taper might help. Cool build!
ReplyDeletei have (built) this one: Seppuku Space Fuzz
ReplyDeletehttps://imgur.com/a/EsEAzM4
How would a 4.7v or even a 9.1v Zener diode affect this build?
ReplyDeleteD3 and D4 is hard clippers to ground so I think you can use 4,7 zeners there. D1 and D2 is a bit more tricky since they affect the the Overload control and octave up. 4,7v Z might work but I wouldn't bet my money on it since it is a DBA design after all....
DeleteMade it too now. Used MPSA06's and a LM386. Glad I had a frw 3,6 zeners from my a Space Ring build. Works great - reminds me a bit of Fairfield Unpleasant Surprise when the Overload is engaged.
ReplyDeleteI built it today. Sounds truly disgusting. Thought exactly the same thing about it sounding like the Unpleasant Surprise.
DeleteJust checking on orientation of D2...cathode facing north, yes?
ReplyDeleteNo, it is facing south.
DeleteHello again! I've replaced the diodes with 3.6v ones and the tone is pretty spot on! The only thing now is the amount of gain. Mine doesn't seem to have as much gain as the original. Got some MPAS06 and they don't seem to work. I have some MPSA05 on the way.
ReplyDeleteI just happen to find one MPSA05 in my stash and the circuit only really works well if it is in the 2nd position. Swap them around and it's really full sounding with no gain!
I'll check over my board and connections again but I'm quite confident that it's all good.
Question... do those caps have to be ceramic? Or would film box caps work just fine? I know that ceramic caps can have certain characteristics that might be desirable here. Thoughts?
ReplyDeleteNo, they don't have too. I used WIMA film caps in my build. Multilayer caps was used in the unit we traced. So both works. I bet the audiable difference would be neglible in this type of circuit.
DeleteBut that's just mine opinion...
Also, looking at the tagboard, it seems like you have the 2n5817 inline protection diode, but the schematic shows a 1n4001 from + to gnd for protection. Not a big difference, but there might be some confusion if people are not familiar with both methods of protection.
ReplyDeleteLooking at the schematic posted and the tagboard, should the 4.7uF and 100uF in the top right part of the board be switched? That 100uF there connected to pin 5 of the IC is supposed to be 4.7uF according to the schematic. And the cap attached from pin 7 to ground is supposed to be 100uF.
ReplyDeleteThat's a some typos in the schematic. I'll try to swap the caps later today. The layout refelcts the actual trace.
DeleteThanks for the feedback. Please update once you fix the schematic. I will note that on my end for now. I am working on a PCB layout for this.
DeleteOk, schematic updated. I don't have access to the first schematic since I didn't draw it put I made my own version during our trace session. It doesn't look as professional as the old one but at leats the cap values are now correct.
DeletePs.
Would love to see how your PCB turns out.:-)
Hi ! Did you try that PCB ? Would love to get one !
DeleteLooking at your new schematic, there seems to be a discrepancy around the Overload pot. On the old schematic (and the perf layout), the 100Nf cap from the emitter of Q2 and pin 2 of the Gain pot goes to pin 3 of the Overload pot and the junction of D1 and D2. On the new schematic, it goes just to the junction of D1 and D2, and pin 3 of the Overload pot is connected to the emitter of Q2 and pin 2 of the Gain pot. I drew up the differences on a jpeg file, but am not sure how to share a picture with you. Hope my description makes sense. If the board is correct, then the new schematic has an error. Trying to make sure I get this right for the PCB layout. Almost done that, BTW.
ReplyDeletehttps://imgur.com/p1x50yf Actually, there you go. That is the issue. Have a look. The old schematic matched the vero board, but the new one needs to be changed as per the purple line. Unless I am missing something. Please confirm.
ReplyDeleteAnother question, if you will... that first schematic that was posted noted all ceramic caps other than the electros. Is that correct? Looking at the 220pf, it is sized for a ceramic disk, but the other caps look like film caps in your drawing. Do you think ceramic is necessary for this build or would box film caps work just find, likely?
ReplyDeleteWell, spotted. Now fixed:-)
DeleteFor the cap types. Yes, all cap except for the electrolyctic were MLCC with 5mm pin spacing except for the 220pF. I guess you could use cermapics or film without much or any audible difference.
Looks like you still need to take out the connection from Gain 2 to Overload 3 on the schematic.
DeleteWhat is the best way to share the PCB layout with you?
Ooop:-/ Now that is fixed as well.
DeleteYou can send the PCB layout to this e mail address.
anders.sjodal at gmail.com
Success! I used MPSA06 in Q1 and 2N5088 in Q2. My PCB layout with board mounted pots was a success. I get all the wicked blooming and cutting out of the signal with the Overload adjustment. The only change I would implement is switching the Overload leads for a more intuitive rotary pot adjustment. As is, it works as the sliders to, with the overload going backwards or to the left.
ReplyDeleteHi everyone, anyone finaly made a PCB out of this ? Thanks !
ReplyDeleteI have etched and proven my layout.
ReplyDeleteHere's mine...
ReplyDeletehttps://photos.app.goo.gl/tDPDBHubdrHLesy39
https://youtu.be/z5DzlBaGqm0
I had none of the right parts for this circuit but went ahead anyway. I used 5088's and 5.1v zeners as I was out 3.6v. Sounds as it should. THNX!
ReplyDeleteYa know when you don't feel totally satisfied for no real reason? For fun I stuck a 2kb pot on the power and starved the circuit a little. I'm getting Lo-Fi square wave as well as some down octave and even a little asymmetrical tremolo (I found it twice, so it's not a weird phenom.). Starving the power just a hair also gives a slightly sweeter sound when you want it. All the pots are interacting nicely. I also changed the Fuzz pot to a 500ka and the Overload function I changed to a 1mc. I liked the circuit as it was but now it has a touch of Dwarfcraft for flavor. Worth a try. Thanks again
ReplyDeleteTurn this into an Evil Fuzz by changing the Gain pot to a trimmer and the overload pot to an on/on switch (spdt will do) with a 250K resistor on one side, and an 820K on the other.
ReplyDeleteInteresting. I may try that. The circuit is sitting on my couch.
ReplyDeleteI built it, fire it up first time and it works
ReplyDeleteAnd I make the enclosure like cabinet amp to make it cooler,
Sounds a bit ring modish,
pretty fun to play
Thank you fuzzhead🙏🙏
https://youtu.be/tg-KsTPTA7g