A pretty cool lookin¨take on the ol¨Big Muff. The first and the last stage is replaced by a dual op amp, a diode lift switch at the the first clipping stage, a Gain control that biases both of the clipping stages and for the tonestack, a James control network is used for invidual bass and treble controls. .
Schematic is avaiable HERE.
Could I use two pots for the dual gang until I order one, or do the gain stages have to move in unison
ReplyDeleteYes, you can use two individual pots with no harm.
DeleteBuilt this tonight with the two 100k pots. Used a tl082 instead of the 72, and 1n4148 for the clipping diodes Oh and added an extra column to run 4.7nf in parallel wirb in 330pf and a 470pf with a 30pf for those odd value caps (I’m sure 4.7 and 470 would’ve been fine but seemed easy.). Getting a fair amount of hum and no effect. Getting signal, volume and tone pots seem to be working. Thought the voltage at pin 8 seemed low at 5.93 but wasn’t sure rest of the ic seemed ok in the 4-4.5 range both transistor collectors are at 3.93. It’s almost 2 am I’ll have to come back to it tomorrow night, I’m sure it’s something I’ve got wrong somewhere.
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DeleteLayout seems to be ok looking at it, I reckon there's a short or misplaced part on the build. Just check adding the extra column hasn't done an unintended effect. And signal probe it following the schematic. TL082s are noisier than 72s btw.
ReplyDeleteThis is beyond noisy. I went through the build everything looks right to me. Checked the layout vs the schematic as well and everything looks right. There’s two spots where it goes resistor cap where on the schematic it goes cap then resistor but I don’t think that should matter. Knifed my tracks just in case, won’t be able to actually audio probe it til the kids go to bed tonight, since there’s signal passing through I should be able to at the least figure out where the noise issue is. The extra Column is literally just added at the end the 500pf and 5nf caps are on the far right so didn’t think that would mess with anything. I’ll swap out the ic as well, just have a pile of 82’s I never use figured a muff would be an ok spot. .
DeleteWell you can mark this verified. Cold solder joint some where I haven’t found it yet. But soon as I audio probed it it started working awesome. Guess I’ll just touch up any suspicious looking spots. And now it’s working perfect. Sounds awesome too.
ReplyDeletealso built. not getting much from the gain control, at least nothing audible. it's making less than 1v difference on the collectors of Q1&2. might be an error in my build, but I haven't spotted one yet. also, I'm not very familiar with the volume control in this circuit, but even with the knob completely CCW it's still much louder than unity gain. anyone know if that's normal?
ReplyDeleteFully ccw I’m pretty sure I’ve got no volume on mine. I’d have to double check that tonight but I’m pretty sure. Also I can tell the difference in the gain controls. I’m using two 100k not a dual gang
DeleteWell I was pretty sure. And I was pretty wrong. All the way ccw is pretty close to unity for me as well.
DeleteI think if you just lowered the value of the pot it would drop the volume of the pedal don’t think it would take it to 0 if it wasn’t already going there though. Curious now to try factory Black Russian and see if it goes all the to nothing at ccw.
Deletethis is the first muff I've come across that has a "level" control like this. even on an op-amp muff, they are just a straight forward volume pot after the coupling cap. according to a user on FSB...
Delete"it's directly linked to the output level of the effect. not using a divider as a volume at the end of the effect, but rather playing with the gain of the last "buffer" stage allows you to have a constant (and very low) output impedance"
so i dunno. maybe it's working as it's designed to?
Yea I hadn’t messed much with it until you said that was playing with the other stuff. I may lower the pot value on mine as it’s really loud now that I notice it.
DeleteQ1 goes from about 3.5-4.8 on mine.
ReplyDeleteyeah that sounds about right. just not making an audible difference in my build :/
DeleteI can hear it it’s not super drastic. I thought it seemed more noticeable with the sustain up higher. I’m curious to see how it works with the dual gang. Should be here Friday. I’m looking for a muff with a different tone control at the moment. This fit the bill. I had already thought about just kind of finding the gain setting I like and put in a fixed resistor.
DeleteSo I ended up doing the following to mine. Removed gain pot completely as previously stated seemed essentially useless, changed the 100k for q1 to 3.3k and the one for q2 to 8.2k. Then removed the volume pot. Changed r25 to 150k. Ran the output to lug 3 of a 100kb, lug to to output, lug 1 to ground. Volume control is much better now. Pedal isn’t nearly as loud but is as loud as I need. I just removed the volume pot from the wiring and ran the wires to breadboard and changed the resistor value til I got to what I was happy with. I probably could’ve just went with 100k but figured I might as well make it a little louder.
ReplyDeleteThanks for the report!
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