Okay, I have tried to build this thing three times to no avail.
Has anyone actually managed to build one from one of the schematics out there? To refresh, I have a real one and I would LOVE to have a clone in a smaller box so it will fit on my pedalboard.
Has anyone designed a PC Board for it? I could try yet one more time, copying the board from my original, but it's at the studio, not on my workbench....
I'm getting very very frustrated with this project and I keep revisiting it every three months or so, thinking that it will work one of these days, but it ain't happening...
By the way, the sound that I just got out of the circuit I just built passes a garbly futzy signal. I put a test probe to the circuit, tracing where things start to go awry, and when I tap off pin 1 of the first op amp, it sounds scratchy and bad. Pin 5 is even worse. I'm assuming the issue is there in the first op amp. I'll check the power again and make sure that's happening.
Roger
Which schem are you using?
Are you perfing or PCBing?
Is your Vr correct & going to the right place?
Do you really gaze at your shoes while you play?
Regards
RDV
Quote from: RDVWhich schem are you using?
Are you perfing or PCBing?
Is your Vr correct & going to the right place?
Do you really gaze at your shoes while you play?
Regards
RDV
I'm perfing, but should be breadboarding.... I believe the power supply is hooked up right... +9v at pin 8 on the 4558 and pin 7 on the 741 and pins 4 to ground.....I don't gaze at my shoes, I stare at the ladies and make them crazy with my wild Fuzz Probing.
Or something.
Roger
I also tried to build the op-amp big muff some time ago with similar results. At the time I assumed I'd just built it wrong (and sometimes breadboards can lie!)
Looking at the schematic I find myself suspicious of the Fuzz pot wiring, intuition tells me the 47k resistor should go to ground or the first Vr but I'm just guessing here, it's probably right.
Pin 1 of the first op-amp (through a cap and resistor) is used for the bypass so if you're not getting a clean signal there, you're in trouble.
What I find most interesting about this pedal is why and how EH created a pedal that sounds pretty much the same but has a completely different circuit.
Anyone actually got one to work?
EDIT: are you using this schematic? I only had the philpott one before
http://members.chello.at/anubics/html/schematics/EH_BigMuff_OpAmp.gif
I've tried both the Phillpott and the Anubics and haven't get either one to happen yet.
Roger
Quote from: Rodgre
I'm perfing, but should be breadboarding.... I believe the power supply is hooked up right... +9v at pin 8 on the 4558 and pin 7 on the 741 and pins 4 to ground.....Roger
I guess I meant the Vr or half the supply voltage(at pin 3 of both OAs) that OAs must have to do their thing.
I've got a 'Fuzz Probe' too, but I won't go into that.
Regards
RDV
Quote from: RDVI guess I meant the Vr or half the supply voltage that OAs must have to do their thing.
So maybe that's the issue? These schematics don't establish that I need to devise a Vr from the 9v supply. Actually, that Anubics schematic doesn't even include power supply connections, so what's the deal there?
Roger
(http://www.diystompboxes.com/pedals/lbm.gif)Have you tried this one? I'm going to.
Regards
RDV
nevermind,
I'll try that now
Roger
Let me know how it goes.
I don't know that my Transistor BM is 'right', but it IS muddy.
The OA versions I try never worked out either...
A while back I was trying the OA muff stuff.
I would like to hear that somebone's actually sorted this out and gotten a usable [Similar to Orig.] Muff typ tone from one of these OA, BM schematics.
Okay, bit by bit, I'm trying the circuit from the Little Big Muff schem.
So far, I have wired up the first dual op-amp. Now, just to see that I'm in the ballpark, I have tapped off of the output of that op-amp (pin 7) just to see that I'm getting signal.
I am getting a sick fuzz, but I'm also getting an unstoppable, unchangable oscillation. The oscillation is at a lower note.
What's the deal? any ideas?
Roger
add the 1uF and the 8.2k and listen from there
I forgot to mention that. I do have those two components hooked up. It's still oscillating. Hmmm..... Very very frustrating.
Roger
Maybe the 741 stabilizes the circuit.
It seems like it shouldn't be fuzzing at all since all the diodes are in the second OA.
You've got the first OA grounded, right?
The super fuzzout/oscillation is occurring on the far side of the 10K that's coming off of pin 1. Pin one gives a clean signal. As soon as we pass the 10K, it's mahem.
Thank you so much for walking me through this.
Roger
What voltage are you reading at pin 3 ?
from the 10k on the far side of pin1 you are going into pin 5, right ?, cause I think pin 6 would cause some oscillation.
At pin 3 I'm getting 4.68v from a brand new alkaline battery.
I just doublechecked and it seems like all is right. It's just super saturated fuzz (not a bad fuzz either) with a crazy oscillation.
Maybe my problem is that I need to build this circuit on a board the size of my head so things aren't so close to eachother. My layout is nothing crazy, as far as parts shorting against eachother, but it's such a pain to troubleshoot when I've soldered everything on this perfboard. I need to breadboard this.
I just have no patience. This is a box that I've wanted on my live pedalboard for years now and I figure, "hey, build it once, and if it works, box it up and take it to the gig." Ugh.
Roger
I can offer no help other than to say my hat's off to you for taking another crack at it.
I've tried (I think) 3 different schematics, including the one posted above, and none of them worked correctly.
What got me wanting to build one was that I bought a factory fresh Big Muff about 20 years ago (probably right before Mike shut the doors) after trying my friend's and falling in love with it.
Mine sounded good, but not the same as his. I did some repair work on his (broken wire or switch or something) and was very surprised to see chips on the PCB where mine had transistors. I would have thought that the older one would be transistors and the newer one IC's, but it was the other way around.
The difference in tone was similar to the difference between a silicon and germanium Fuzz Face. In this case, the opamp Big Muff sounded more germanium-ish. Leads me to think that maybe they used germanium clipping diodes in the one I tried. EH were surely not picky about what components they used. If someone got Mike a closeout deal on a truckload of germanium diodes, he would have used them.
I'm really rooting for you. Good luck.
That's crazy stuff, from EH. I only wish I'd heard an OA Big Muff, I've only heard reissue sovteks with transistors.
Just my 2 cents...
I actually have an op amp little big muff and it doesn't look the same as Tobias', Anubics' or Phipott's. I'm at work right now and don't have the differencies in my head but the input cap is different, so is the V+ supply and the "bypassed" output isn't taken from the first half of the 4558 and so on.... Oh, the clipping diodes are silicon.
Somebody did the worst soldering job I've ever seen on this one and the tone switch didn't work so I decided to give it a workout but was puzzled by the differencies in the schematics. It did however work and gave a nice Robert Frippish distortion. Just wanted to fix the tone and use shielded input wire (was extremly noisy) and perhaps put pots for dist. and tone. It is presently dismantled in the to do pile on my workbench :wink:
Best!/
Pelle Garpebring
Sorry, I wasn't clear in my earlier post :oops:
It is just the in/out/switching wiring that someone has butchered with a soldering iron. This needs a rework. The pcb/components are most likely original.
Best!/
Pelle Garpebring
Okay, I took my original BMP home from the studio last night. I started to trace the circuit and it seems similar (I'm not done checking values) to the posted Little Big Muff circuit. I'll do a thorough trace and see if I can't post it.
I was tracing the PCB as well, and I may just go with tightening up that layout and making a clone using the same layout, just slightly smaller to fit into a 1590D.
I think mine had been modded before I bought it, as someone swapped out the input cap for another value, and the in and out wires are shielded.
Everywhere I turn, it's frustrating, though. I hate to whine, but years ago, I used to do PC layouts in my sleep using CorelDraw. I loved it. I could do a decent layout in a couple of hours. Now, I'm using an Imac (which crashes constantly, despite the fact that it's always in the shop) and I've shoehorned Illustrator on it to do PC layouts, and I'm nowhere near as used to using Illustrator, so it's a total pain.
I've downloaded a mac-based PC layout program and couldn't figure that out for the life of me, either. I come from a graphic design background, when it comes to computers, so zipping around with Corel was a breeze. Someone have an old PC they want to get rid of? :)
Back to the workbench before my next session.
Roger
This is one of the most frustrating things I've ever tried to do.
I just perfed a circuit, copying the layout of the original Big Muff that I have and I still get nothing. I must be doing something completely stupid because this is the fifth time i've tried to do this.
the next thing I can do is to make a 1 to 1 copy of the board layout and etch it and try it that way, but honestly, I don't have that kind of free time for awhile... a week or so.
Now I know why people who know how to DIY their own pedals STILL pay $200 for a boutique box. I've probably spent about that much in time in parts trying to clone this blasted thing.
That being that case, I'd just as soon buy another vintage op-amp big muff and repackage that (I still want at least ONE original one) to put on my pedalboard. Anyone have one they'd part with? I just won't eat this month, and I'll give you the next $100 that passes through my hands.
It's not like I'm trying to clone a friggin' Microsynth. It's a fuzz box! It's not that complicated.
I hang my head in shame and I hang up my soldering iron. Time to go to work.
Roger
Roger:
Have you done much with OAs in the past? Pinouts can be a bitch, also: what are the OAs in your original unit?
Regards
RDV
Yes, I've done a lot of stuff with OAs in the past. I can recite the pinouts of 741s and 4558/1458s in my sleep! That's why I feel like such an idiot!
My original has a 4558 and a 741. I'm using the same, and I've even swapped out different ones in case the first ones I tried were defective.... no difference. I must be doing something ridiculously stupid. Can you sense my frustration? I've been DIYing pedals for seventeen years now! What about this am I missing? It would be comical if I wasn't so seriously frustrated about it.
I'll try again when I get home from my session tonight, but I feel like it's a losing battle.
Several times I've tried to build this one step at a time.... meaning put together the first section of the first op-amp and see if it's passing signal. I lose it somewhere after the first section.
Roger
This may sound crazy, but try going into the non-inverting input on the first opamp section, just reverse it. Maybe both sides of the 4558 need to be running into the non-inverting or + inputs like on a tube screamer. It could be whats making all your attempts go bad. Forget the schematic! Inputs into + & feedback loops into - like a tube screamer.
Regards
RDV
Hi Rodger,
I once had an Op-amp Little Big Muff which I cloned so I could have a mini Big Muff. Any way I still have the diagram I did from the Little Big Muff if it's any help.
I also encountered crazy oscillation in the second stage of the 4558 with the clone and recall having to raise the value of the 0.01uf cap to something like 0.047uf or even 0.1uf.
-Dave
Dave, could you please mail me a copy of the diagram you did for the little big muff? As stated in my earlier post, I have a little big muff that doesn't seem to exactly match the known schematics. I'm really curious of what I have here. Is it modded or are there several versions of the op amp circuit? Plus, I need to remove it from the to do pile and onto the pedalboard. :)
Thanks in advance!
Best!
/Pelle Garpebring Grillbeppe@hotmail.com
Quote from: RodgreYes, I've done a lot of stuff with OAs in the past. I can recite the pinouts of 741s and 4558/1458s in my sleep! That's why I feel like such an idiot!
Is there anything that you want me to check on my Little Big muff that can help you?
i still have the pedal around.
Tobias Karlsson in Sweden
Thanks Tobias! Tackar!
If yours look exactly the way it does in your schematics then I'm still confused. Mine is just a little bit different, have to draw it up in order to point out the specifics... It has a different input cap, the V+ supply goes after the 47 resistor to the other points, not straight from the 9V, other different caps and so on. It doesn't look like its modded on the pcb though. Anyhow, it is working, it just needs a resoldering of the in/out/switch. When already having it open on the bench, I thought of improving it a little. Shielded cable on the input (it is good sounding but noisy as...), true bypass ( another thing that is different, mine doesn't have the bypassed signal taken after the first 1/2 4558 but from the input of the entire circuit), maybe tone/dist controls and try original values IF there is such a thing :) So I'll get back when I have thought some more.
Best! Ha det!
/Pelle Garpebring
Maybe I shouldn't type on behalf of the other OA muff wanterz.
But I would like to see something tonally close to an OA Big Muff WithOut the buffer bypass, or any other schematic anomolies.
I guess I'm easily confused, but still prefer to build ckt's without Any bypass switcheing on them...
I can get past them usually, but sometimes they're 'folded' so many times, they're very difficult to follow [Bear Face] or tied to the ckt in a way [BM] that makes it necessary to re-sort that entire portion of the ckt.
I think most of us prefer TB on our ckts, to prevent altering or tone sucking off of the signal path, all that other stuff becomes a moot nuisance except for the repair of original aspect.
Okay, I found a stupid missed connection so the 741 wasn't getting power.
Now I have fuzz, and the controls do what they should. The only problem now is that it oscillates like crazy.
Any ideas? Could it be the layout? I followed the general layout of the pcb of the original, trying to avoid this. What would cause oscillation? Is there a cap value I should tweak?
Roger
I increased the value of the cap between pin 5 of the dual op amp and ground and that took care of the oscillation. It's pretty much working now, except it doesn't sound quite as chewy as my original. It could be tolerance of components. There were a few that I changed the value of because I didn't have the correct on on hand, but I kept it close. The fact that I did this build-up on solderless perfboard and it's finally sort of working...well now I have to build it again on a more permanant board.... Time to try to PCB layout. I won't have time to do it right until next week.
At least it's sort of working, even if it doesn't sound 100% yet. Thanks for all of your help.
Roger
How different from Tobias' schem is what you did? I'm dying to do one myself and I want to take advantage of all your hard work :wink: .
Regards
RDV
I think it's the same as Tobias' schem.
R17 is definitely a 47 ohm on mine.
I didn't do the "dotted-line" suggestions, as I followed the layout of my original.
Roger