Muff Schematic vs Original Schematic

[Anonymous]

So I was trying to see what I could do in order to get this build to sound as close as possible to the original, and ended up going through both schematics.  I found that the resistor – R25 – on the GuitarPCB schematic isn’t in the original schematic, and the electrolytic capacitor for the power circuit is 22uf in the original vs 100uf in the GuitarPCB.  I’m assuming the resistor is there for some protection?  What are the risks if you just put a jumper in place of it?  Also thinking the reasoning/designing the clone for using the 100uf instead of the 22uf is just another way of doing it or added protection?

[Chuck]

When you are looking at the schematics on Kit’s site remember that they are for the original Muffs that range from old to fossils.  Barry’s boards seem to be more modern ‘works like’ versions of the old circuits.  The 100uf in C15 is going to give you better power filtering.  I’m honestly have no idea what R25 does but 33k is specified for all versions in the build document – rather than soldering in a jumper I would put in a socket so you can check out the jumper, the 33k or something else until you get the sound you’re hunting for.

Chuck

[Cybercow]

When I built my first Muff’N, I also found Kit’s and the Coda-Effects sites for their schematic references on a BMP. The first thing I noticed was that the part IDs do NOT match. So I printed out several different schematic from Kit & Coda, then printed out a larger version of the Muff’N. Then I started mapping all the different part IDs onto the larger Muff’N schematic. With that freshly marked-up Muff’N schematic, I was then able to cross-match all the various parts and compare values in the Muff’N’s BOM options list. I found several components were very close in value while others varied wildly in their respective values. (That’s where the different BMP versions were given rise.)

R25 was added to the Muff’N to better cope with different gain values of the selected BJTs used in the project. Without R25, depending on which BJTs are used) the gain can be pretty hot and R25 is just there to tame the levels. Use sockets for R25 and test different values or even a jumper. It won’t hurt the circuit but can make it sound different. That final cap is important as it prevent DC from directly reaching the output.

Hope this helps.

[Author]

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