First pedal from scratch - modified muff

[yung_bukowski_420]

My roommate asked me to build him a big muff with a starve control and a three band EQ.

So i sketched out a design based on what i know (i've built one pedal from a BYOC kit so i am new to this stuff) and here it is (please let me know if i've made any grievous errors, haven't breadboarded it yet):




Now my roommate is saying he wants me to add an octave up control too! i'm thinking that'll be after the output of the muff on a separate footswitch? anyone have any experience implementing this? can you offer some advice or example circuits?

[mth5044]

Your bypass scheme is a bit different. Typically, you want the input jack connected to the common of the switch then the bypass and the effect input on the two poles. Then you can leave the top pole of the LED switch unconnected. You can also look into 'grounded input' true bypass that is commonly used on high gain circuits and in general.

I've never seen a 20u cap on the bypass signal before, perhaps you meant that for the +9V?

Why are you using two series 1n in each gain stage instead of a single 500p cap? You will save space and money using a 500p.

You could also scale the tone stack by multiplying the value of each cap by 10 and dividing the resistor values by 10. I believe it has something to do with noise, not totally sure, but it is a common recommendation. Check out the Duncan Tonestack calculator for value tweeking and whatnot. The last transistor stage is partly meant to recover losses from the Tonestack, so you can see if the gain needs to be altered by comparing the signal loss of the fender Tonestack to the normal big muff tone control.

[yung_bukowski_420]

Thanks for the quick reply Matt.

Yes! The 20u cap is supposed to be on the +9v. My mistake. Good catch, thanks!

I was under the impression that the two caps in series had something to do with the sound, having copied that portion of the circuit directly from the schematic of a civil war big muff.

As for the bypass scheme, i copied it from BYOC. I built one of their kits which is where i learned how true bypass works. However your suggestion seems simpler!

As for the tone stack, i'm going to breadboard that out ASAP and test it. Will definitely try tweeking those values.

[duck_arse]

y_b - you will almost certainly need a blocking cap at the base of the last transistor, as all those pots are in parallel w/ the lower biasing resistor.

and just to be really picky, and to mess the neatness of yr diagram, it is best practise to draw multipole switches so that all the poles are facing in the same direction. your SW1A operates opposite your SW1C, and pickier still, your SW1B is not marked.

I always connect the multi-poles on my diagrams with a dotted line. a very old habit, not seen too often these days.

[edit :] when I say all the poles facing one way, I mean having all your N/O (or N/C, your choice) connections drawn over (or under, choose), and all the N/C connections drawn under. or the opposite. just in case that wasn't crystal.

[mth5044]

Thanks for the quick reply Matt.

Yes! The 20u cap is supposed to be on the +9v. My mistake. Good catch, thanks!

I was under the impression that the two caps in series had something to do with the sound, having copied that portion of the circuit directly from the schematic of a civil war big muff.

As for the bypass scheme, i copied it from BYOC. I built one of their kits which is where i learned how true bypass works. However your suggestion seems simpler!

As for the tone stack, i'm going to breadboard that out ASAP and test it. Will definitely try tweeking those values.

The bypass is correct, it's just a different way of showing it than I was used to!

I have no idea why those 1n are in series other than to get 500pF of actual capacitance. If you want to an exact clone of the civil war (which you won't with that tone stack!), I could see why you'd want them in, but it seems ridiculous to not use a 500pF in place of the too film caps. Either way, it's not 'wrong' to put two 1n in.

Not sure what DA is going on about with the switches 

Nice looking schematic, btw. Things always look nicer in pencil.