Saturday, 1 April 2017

21st Century Big Muff

Mictester's version of the Big Muff.
You can find the original FSB thread and schematic here.
I've used the updated schematic on page 2.

21 comments:

  1. Needed something to build today, so gave this a go. Tag it verified! This is one badass muff variant. Really great pedal. Transistor pin outs are the wrong way round which didn't take long to figure out thankfully. Mine seems to take a few seconds to fire up but when it does WOW! Thanks as always Alex and all those great guys on FSB.

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    1. Good Lord Gavin! That was quick! Do you mean the transistors Emitters and Collectors should be inverted?

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    2. Yes, Emmitters and collectors should be inverted. I couldn't resist as i do like a good big muff.

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    3. I'm not sure. That would connect the 6K8 resistors to the Emitters instead of the Collectors. Have you checked the pinout of your transistors?

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    4. Sorry, my mistake i seemed to have them the same orientation as the layout. Think i'm starting to loose it.

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    5. Is there a reason i have low volume output? How could i get more hesdroom out of this effect? Im also confused what the LED is doing attatched to the board. Is it supposed to stay on? What is its purpose if it doesnt tilirn on and off with the effect? The traditional side sounds pretty good, but is the jumbo side supposed to sound super fartty? Any help would be appreciated, thanks!

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    6. there has to be an error in your build if you're getting low output and it sounds farty. i suggest checking that all your components are in the right place and run a knife between all the tracks. the LED that's attached to the board is supposed to be for the indicator, and should not be on all the time.

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    7. Thanks. Ill check my lagout again. Do you think the fact that i used 5089 tansistors instead of bc550's has anything to do with if? Any other suggestions for a replacement for a bc550?

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  2. What's up with the 4 gain lugs going to 9v. I have never seen that before. Does that make the distortion better or does it make it have more gain. Would this be a high gain pedal.

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    1. The switch changes the resistors used to connect the transistors' collectors to the 9 volt supply.


      This is what the designer of the circuit said on the forum post :

      "I revisited this circuit over the last few days. It occurred to me that one of the biggest changes that you can make to the clippers in a Big Muff if to vary the collector resistors (try 4k7 or 5k6 all you "low gain" freaks and prepare to be pleasantly surprised!). I had a supply of 100k dual log pots (used in my mixers), and decided to try making the collector resistors for the clippers variable. My first attempt tried using a single pot (I'm cheap like that) but it wasn't terribly good. Going for the dual pot, wired as two variable resistors is amazing - it goes from less than the usual Big Muff tones right up to an uncontrollable screaming monster!"


      And yeah, it would be a pretty high gain pedal. It's a big muff, after all.

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    2. Thanks for the info got it now.

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  4. There ist never enough muff, got to try it.another one for the list!

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  5. Thanks Alex! Since I requested this, I'll have to try building your layout. As you mentioned in the post, there's a nice FSB thread on this muff variant - definitely a cool take on a well-known circuit.

    As for the transistor dual pot gain control, I would probably consider using a DPDT switch to flip between a low gain mode and the standard mode with fixed resistors (standard mode has collector resistances of 12K for Q1 and 22K for Q2, according to an older schematic in the thread). The switch would be wired where the Gains 1 and Gains 4 control wires are on the layout.

    "There ist never enough muff..." Comment of the day :)

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  6. What would happen if a 500k dual pot was used for Gains instead of 100k pot? (Asking because I happen to have a 500kA pot collecting dust.) Also, are there any recordings yet?

    Thanks for all you do. Love the sight!

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    1. You would need to add a 56K resistor across lugs 1 & 3 and another one across lugs 4 & 6.

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  7. So.. 50k (layout) or 100k (as it seems here in the comments) for gains?! :D

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  8. It's the Current Limiting Resistor.

    Any resistor from 2.2k up to 10k can be used, though 4.7k is what I see most often.

    It controls the amount of current going to the positive side of the led to stop it from burning out, as the current would be too high without it.

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    1. Thanks! I dont understand what that LED is doing tho. I have this wired up for true bypass on a 3pdt footswitch, and dot see the function of the one connected to the board. Should it be coming on and off via my footswitch? Or is it supposed to stay lit, as it is. Also, i do have this effect working, but not sure its sounding correct. How would i get more output volume as i have the volume maxed and still need a lot more headeoom. Any help would be appreciated. Thsnks!

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    2. Also, my gain, which is a dual gang B100k pot, doesnt seem to do anything on the traditional muff side. Is the jumbo side supposed to be super farty snd flabby? I am using 5089 transistors, as i dont have any 550's, but other layouts seem to use the 5089 in place of the 550 so im not sure if thats creating my issues or not

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