Update 2 210514
Both schematic and layout is now corrected. A big thank you to Vince who traced the later 125b version which revealed how the active Mid control really works.
Update 1 210514
Caution! There was a mistake in the trace. The Mid control have a different setup than the schematic and layout below indicates. Do not proceed if you want a Mid control that is 100% identical to the stock ODB. I will update the the schematic and layout as soon as I can. Lesson learned, hesistant to trace from gutshots from now on...
Intended for bass but works really good for guitar as well. Based on OCD but tuned for more low end, headroom and gain. Treble and Bass controls is a passive James tonestack and Mid control is an active Bridged-T feedback control. Cut switch is Shelving filter for the first gain stage and Clip switch selects between assymetric MOSFET/Silicon, LED and none clipping. Traced by AlexS and fuzzhead and the layout is verified.
Two things, though. We couldn't figure out the value of the Treble cap in the James tonestack but values between 330pF and 1nF sounds good.
Also, the LTC1144 charge pump is only needed if if you want to run it on 18v to get a 36v swing within the circuit. They are pretty expensive and not that common. MAX1044 and ICL7660S can be used as well but the cut between pin 1 and 8 of IC2 must be omitted. Those charge pumps can only handle a maximum input voltage at 10v and 12v respectively so a 9v power supply/battery is higly recommended...
You know I’m gonna have to build this . Just because it has the word bass in it.
ReplyDeleteCool! Looking forward to hear your thoughts about it.
DeleteAnd Dunwich Volt Thrower is in pipeline as well. A bass Rat with the same passive eq section as above and a 6 pos rotary clipping switch...
Thanks for posting this! it fired right up. used the max1044 and a JRC4558D. The treble acts alittle funky. i socketed the cap and tried a few different values in the range suggested but it squeals past 50% rotation on the A1M regardless of cap size. either way, works great on my active bass (no squeal) and sounds mean!!!
ReplyDeleteYeah, there is something funky with your Treble pot, no squeal here. Not sure what the issue could be...??? Do you have a TL072 op amp lying around to try out?
DeleteI did try the 072 and got the same issue. It is certainly all on my end. Seems like all my stuff has been squealing lately. might be a bad batch of components i need to identify, but like i said, no issues and sounds HUGE when my bass is
Deleterunning through it. Thanks again Fuzzhead!!!!!!
I get some squeal also when everything is cranked, but I'd usually not do that with this and it's also still unboxed. I tried a Tl072 and OP2134.
DeleteThanks for the layout!
I discovered that was it also! ive had my amp set on a real low volume and have just been dimeing all the knobs into unrealistic settings to hear everything haha.
DeleteOoo, looking forward to pairing with the volt thrower
ReplyDeleteAm I losing my mind or are there only 10 links?
ReplyDeletejust built it and there are indeed only 10 links
Delete10 links indeed. Will update it when I get home tomorrow.
DeleteNice one. Looking forward to building this up and putting it up against my Fuzzrocious Demon.
DeleteWhat's your Fuzzrocious pedal like? Have you ever traced it?
DeleteIt's great, one of my go to bass/guitar drives. It has that OCD sound, but can be more aggressive and retains the bottom end more on bass. I've not tried to trace it. Might drop it into one of the forums.
DeleteI am interested too by the fuzzrocious stuff. By the Bongripper's one. The OCD and RAT with blend. Demon and Cat tail i guess.
ReplyDeleteI have try to simulate this with Amplitube. Very interesting blending sound and i guess it will be better with analog pedal.
I will go to have a look on this.
Diode 1N4001 is inverted in the schematic, isn't it?
ReplyDeleteYes it was. Just flipped it over. Thanks.
DeleteJust finished this up and can already say it has kicked the Demon into touch. Does everything it can do, but more (and louder). Used 2n7000 and they sound fine. Got some bs170s on the way to compare. I initially used a MAX1044 but it squealed like hell, dropped in a LT1054 and it’s completely silent. Only tried 1nf on the treble cap and it sounds good to me, gets bright enough. Will get it boxed up and it’s going straight on my bass board.
ReplyDeleteThis comment has been removed by the author.
Delete@Fuzzhead. Looking for a little advice. Im sure you have probably built this and the Volt Thrower. Do you think its worth the time to have both. I have built the Volt Thrower and love it but Im wondering if there is enough difference between the 2 to make building this one worth while. Also are 25v caps enough for this seeing as though it does the 18 / 36 swing thing. Does the Volt Thrower work this way to when you put 18v to it. Sorry for so many questions , this is my first journey into anything over 9 volts and I dont want to smell my cooking. Im running the VT at 9v while Im waiting on my LTC1144s to show up and I built it using 25v electrolytics.
ReplyDeleteHello Matt!
ReplyDeleteYes, I built both of them and IMHO it worth building both especially if you play bass;-). Yes, they are pretty siilar but the feel and texture is quite different. Also ODB has an active Mid control.
I should have mentioned in the Volt Thrower post about the minimum recommended voltage ratings for the electrolyctic caps. The power section behaves and is identicl to ODB. You can get away with 25v caps if you running it on 9v (18v swing). For the Volt Thrower I think you need to sub the small electro cap for a higher volatge value if you want to try it at 18v. The 47uF caps can be min 25v since they are before the voltage converter and don't do the "swing" thing.
So if I were making an ODB I could use the exact same power section schematic as shown in the VT schematic?
DeleteSorry to add a lot of confusion about the power section...first time working with this charge pump...:-/ Yes, you need to remove the cut between pin 1 and 8. Then the power section is the same as in the VT (as it should) except for the electro cap on the left side.
DeleteHmm, my 2u2s are rated for 35v probably not enough though . Probably should go to 50v
ReplyDeleteSwitched out, good practice for mistakes,lol. 1144 should be here today. From what I hear the VT is supposed to sound even better at 18v. I’m going to build this as well. The owner of Dunwich posted a diy OSHpark bass overdrive project on TalkBass recently . I have 3 boards headed my way to try out.
ReplyDeleteThanks for the tip. In the TB thread, he says of the DIY project "It's mostly a Boss ODB3 with some modifications to tame it a bit in terms of gain and expand it in terms of EQ."
Delete