custom fuzz build question

[rocket8810]

so guys got a question before i start breadboarding a big project. so i'm working on a build for the bass player of one of my favorite bands. basically he wants a si fuzzface with a clean blend, and be able to control the rolloff frequencies of the output.

the tone is easy by making an output cap blend, since the volume pot and output cap essentially make a low pass filter. the big issue is the blend, since using a buffered blend will make the fuzzface not really sound like a fuzzface.

with that being said, i've been doing a bunch of research and came across the smallsound tafm, which is essentially a brassmaster input blend section and a heavily modded Ge fuzzface. so looking at the schematic i see the output of the fuzz is similar to the brassmasters fuzz output, which messes up the way i had figured i would approach the tone. anyone with more knowledge then me, which is a lot of the guys here, have any idea why. also, if i should plan on changing the output of the fuzzface to be similar to that of the brassmaster will doing an output cap blend still be the best way to approach changing the cutoff frequencies.

for some reason i'm having a huge mental block on this one, and i'd rather have a plan of attack for the breadboard then go at it like the apes in space odyssey.

smallsound TSFM blend section


smallsound TSFM fuzz section


forgot to mention, the schematic came from FSB, http://www.freestompboxes.org/viewtopic.php?f=7&t=22856.

obviously, thanks in advance.

[bluebunny]

Those links won't (ever) work.  1. They're at "the other place".  2. Image links need to point to images, not pages (or anything else).  Try hosting your pictures somewhere else so we can take a look. 

[rocket8810]

Shit. It showed up when I first posted it, so I thought I didn't have to move them over to the other place and post them up.

[bluebunny]

It showed up when I first posted it.

That's because you were still logged in to the other place.

[duck_arse]

.... and i'd rather have a plan of attack for the breadboard and then go at it like the apes in space odyssey.

I fixed this for you. also, anybody trying to access those links will get "not authorised to view". probably unless they are logged in there at the same time.

now, hands up, how many people here would ever do that?

[rocket8810]

well at least i'm in good company, so  i don't feel like a complete idiot. pretty sad that i didn't realize that after the years of being here.

anyways actual pictures of TAFM schematic:

Blend Section:


Fuzz Section:

[antonis]

Sorry but I'm little confused... 

Do you want to control the tone of final output (wet + dry) or just the fuzz one..??

[rocket8810]

just the fuzz.

so essentially the signal will come in and split so, fuzz and clean. then at the end of the fuzz he wants to be able to control the amount of low end and have a lowend cutoff from stock to 350hz. originally i was figuring that by having an output cap blend will allow me to accomplish since the output cap and volume pot essentially make a high pass filter, so changing the cap value will change the cutoff. but, if i take a play from the TAFM, which i described what was done to give a blend control to a fuzzface like circuit, the volume control from the fuzz is completely different, since there's resistor inline with the output cap, and a parallel resistor to the volume pot, which is also exactly the same as the clean volume pot.

i know i missing something stupid, which is why i haven't started breadboarding the circuit, cause knowing me i'll end up hitting a wall.

[GibsonGM]

Why not try blending the clean into the output via a 'fair value pot'?  From the point marked 'send', to one end of a pot maybe 10k.    Other end of the pot takes the output from the volume pot  (I'd try omitting R11).  The output from this assembly is the wiper >> output jack.    If it is too 'bleed thru', try a bigger pot.  20k, 50k.  I bet you'll find 10, or 20k is fine, tho.   Not elegant but should work.

Someone tell me if I am missing something here, impedance-wise or something...

Phase should be ok. 

This is the simple way.  There are others that aren't simple. 

[rocket8810]

i'll give it a try, i mean what do i have to loose if it doesn't work? i think you're right about the phase being alright, and not sure about the impedance either.

what i was thinking is it would be nice if the clean could get boosted, which the brassmaster does, and really the TAFM can do too since it has the clean section, which is why i was looking at implementing the same idea.

any idea for the reason for the change in the volume control from typical fuzzface to that of a brassmaster in the TAFM? typically i can follow a circuit and the rational for certain things, but once i get to the output i'm completely lost.

[GibsonGM]

I'd say the level is probably high.  R9 and R10 are a voltage divider that drop signal level.  Otherwise, it's pretty standard from where I'm sitting.   

To boost the clean, you COULD introduce another stage (mosfet boost?  High input Z to preserve the tone of your input signal) and mix THAT with the output. It could have its own level control.  Mind your phasing of course.     

Another way might be to tap off a previous stage that isn't distorted yet. 

No clue how any of these could affect the tone of the circuit, but yes, as long as you don't short something etc., you are free to try them out! 

[slacker]

any idea for the reason for the change in the volume control from typical fuzzface to that of a brassmaster in the TAFM?

In the TAFM schematic R9 and R10 in parallel with the volume pot form a voltage divider, reducing the volume from the fuzz, it's like have a pot that can only be turned up a bit over half way. The series resistor R11 is to mix the signal with that from the "clean" pot, if you didn't have the resistor and the similar one on the clean side and just connected the wipers of the pots then turning one pot all the way down would mute the other one.

I'd do what Mike suggested, for the clean side build a high impedance buffer or booster and wire the input in parallel with the input of the fuzz face, this shouldn't affect the tone of the fuzz and will keep the interaction with the guitar's controls. Do your low cut idea for the tone control and put a buffer after the fuzzes volume control and then mix the output of that buffer with the clean signal. You might not need the buffer but without it depending on how you do the mixing you might find the low cut varies with different settings of the fuzz volume.

[GibsonGM]

This works very well for splitting a signal without causing any weird issues: http://www.muzique.com/lab/splitter.htm

[rocket8810]

awesome. thanks ian and mike. i didn't think about using the AMZ splitter, and was afraid of using a buffer in front of the fuzzface, as i thought that would prevent it from behaving as normally expected. i'll give it a shot.

now that you say that R9 & R10 acts as a voltage divider it makes perfect sense. i knew i was missing something stupid about it.

so if i go for the AMZ splitter, i should end up with the same thing as the 2nd schematic, but 2 stages not 3 (one to the fuzzface, one for clean), then after split for the clean run that into a booster of some sort. then simply join them with lug 2 of the clean booster joining the fuzz with an series resistor running into an output buffer. the the TAFM is using an Si slitter at the beginning and Si buffer at the output. right? which is essentially the same that's done in a brassmaster, no?

[pinkjimiphoton]

Why not try blending the clean into the output via a 'fair value pot'?  From the point marked 'send', to one end of a pot maybe 10k.    Other end of the pot takes the output from the volume pot  (I'd try omitting R11).  The output from this assembly is the wiper >> output jack.    If it is too 'bleed thru', try a bigger pot.  20k, 50k.  I bet you'll find 10, or 20k is fine, tho.   Not elegant but should work.

Someone tell me if I am missing something here, impedance-wise or something...

Phase should be ok. 

This is the simple way.  There are others that aren't simple.

this way may or may not work. i tried it in a workup of the fuzz section from the old fender fuzz wah that gus had cooked up, and it was completely useless. you could "kinda" blend, but ya lost so much signal it wasn't useable.

in that case, it's cuz of phasing... i believe the input signal and the fuzz output were out of phase, and thereby cancelling each other in the middle.

in the case of a fuzzface, in to q1 comes out out of phase, but when the signal leaves q2, it is inverted again and back in phase with the original signal entering the device.

so in a fuzzface, yeah, a passive blend may just work. i'd probably up the blend pot a little bigger, maybe 50-100k and make sure the pot case is grounded.

good luck mate!

[rocket8810]

thanks guys. so i finally got a chance to sit down at the breadboard and work on the project and have some good news and bad news with my experimenting.

going with something like what's in the TAFM works without changing the tone of the fuzzface at all, which happens when buffer is put in front of it. i've kept the fuzzface as is for now, so it's got a 500k volume pot going into the return. but, i've run into 2 issues, that i'm not 100% on what i should to to correct it.

1: i've got a small amount of bleed through of the fuzz, even when the fuzz volume pot is all the way down and should cut the signal.

2: if the fuzz volume pot is all the way off and i try to increase the clean there's no change in the amount of clean at all. all i get is the small amount of bleed through of the fuzz.

what i've got in my head is that i need to up the 470r resistor that goes from clean 2 that meets the output of the fuzz. any thoughts?

[rocket8810]

never mind about what i said was a problem. i was messing around with my brassmasters and the same thing happens with them when the settings are similar to the breadboarded circuit. just the nature of the beast. and really who's going to take a fuzz pedal and turn off the fuzz and use just the clean. seems to defeat the purpose. lol

[rocket8810]

well after taking it off the breadboard and putting it on the layout it's not working right to say the least. after a lot of debugging and testing, and having a buddy of mine take a look at it and try breadboarding it something must have been off when i did it. the fuzz has way below unity output, and the fuzz pot does jack. need to figure out something else to accomplish the main goal of fuzzface with clean blend/boost.

going to give some of the suggestions a try, but been thinking of a few other things, not sure if anyone has tried them before. here's my 2 ideas

1 - running a clean boost in parallel with the fuzzface. so the the signal comes in and goes to the fuzzface and a boost something like a mosfet boost of lbp/modded hogs foot.

2 - use a buffered splitter (split and blend) or the JFET splitter GibsonGM suggested. i know the fuzzface wouldn't be happy so i was thinking about adding an inline resistor, like 10k, from the bluffered input to the input cap. from some of the reading i've done about mimicking a pickup load, shouldn't doing this do trick the fuzzface into thinking it's receiving signal directly from the pickups. my biggest concern with this is that i'd cut the fuzz signal in order to add the clean, when i would rather be able to keep the fuzz output the same and be able to just add clean to/with the output.

3 - doing something similar to the sparkle drive using an IC buffered clean split off the input. but, looking at the sparkle drive schematic i'm not to sure how the output would be wired, since i need a clean output and fuzz output.

ideas? suggestions? criticisms?

[kat]

I think the overall thing you are trying to do (clean blend with FF) probably comes up a lot.  I was trying to do something similar and some of the discussion is documented in another thread.  I learned a lot from the responses people gave me... so perhaps you will find some of them helpful:

http://www.diystompboxes.com/smfforum/index.php?topic=117038.msg1085740#msg1085740

FWIW I did try a buffered blend and it sounds like complete crap in my opinion.

As you can see from the end of that thread, though, I had some (maybe surprising?) success blending two FF circuits and just dialing the settings for one of them so that it is more of an overdrive.  But honestly that gives more of a range of interesting flavors to the fuzz... it isn't like you can turn a knob and go from clean to fuzz, nor is it like having clean signal truly layered on fuzz.  But if you already have all the parts, you might try it out and see if it works for you. 

I came to the conclusion that if clean blend is something you want, FF is just the wrong fuzz.  Still hoping, though, that someone has the magic secret...