Fuzz Face Clean Up

[Mcentee2]

I know and apologise, but for some reason I really can't find a good explanation of why a FF gets brighter when it cleans up.

I have read many things about impedance etc but they just relate to clean up per se but don't explain the reintroduction of the high end at the same time.

Any links to previous threads would be gratefully received!

[GibsonGM]

I found this on the internet for ya, Mc...close to how I'd have explained it myself, but of course, I have some gaps in knowledge the way you do, so looking it up was safer, ha ha!
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EarthTonesAudio on the Gear Page, 2008:

"There's a bunch of subtle stuff going on so a complete explanation would take many pages. It can be broken down into a few key points though:

First, remember that the guitar pickup, volume/tone pots, and cable capacitance form a parallel RLC circuit, which has some resonant peak. We hear that peak as the guitar's treble content. A high impedance input will preserve the peak, but if you decrease the input impedance the peak will get smaller and smaller and eventually disappear.

The Fuzz Face input impedance is low and primarily resistive, so when you have your guitar hooked up to one with the volume pot up full, it's as if you replaced your volume pot with a resistor of perhaps 1000 ohms. This sucks all the treble out and amplifies what's left.

Conversely, when you roll back on the volume pot, you're introducing resistance in series between the pickup and the FF. This means the guitar is once again able to produce a resonant peak, so the treble content jumps back into the mix. Simultaneously, the additional series resistance lowers the gain of the FF, but not equally across the frequency spectrum. Because the input is where the negative feedback is applied, and because that cable capacitance is still there, the high frequency gain stays high. So rolling back the volume control effectively lowers the gain for bass frequencies only.

So to sum up, when you roll back the guitar's volume knob, you're lowering the gain for bass frequencies in the FF circuit, and simultaneously increasing the available treble content from the guitar. This is a recipe for a thin, chimey sound."

[Mcentee2]

Thanks, that has given me something to look at!

I recall that impedance or reactance, changes with frequency and this also was in the mix between guitar output and Fuzz Face input.

I also have read many posts by Gus regarding looking at the FF circuit and guitar as an inverting opamp style!

[GibsonGM]

Thanks, that has given me something to look at!

I recall that impedance or reactance, changes with frequency and this also was in the mix between guitar output and Fuzz Face input.

I also have read many posts by Gus regarding looking at the FF circuit and guitar as an inverting opamp style!

Absolutely.   The difference is just that the FF is an 'odd duck', and does some things that are counter-intuitive, as you noticed! 

[pinkjimiphoton]

its all them reasons, and then some...
remember, a fuzz is really no different from a treble booster for all intents, with a bigger input cap... bigger cap= more lows, more lows - more distortion.

as you turn the guitar down, you have multiple things going on as cited, but you're also rolling off input frequencies to it with the volume pot... less bass = "more" treble" = less distortion. because its already somewhat of a treble booster, the harmonics tend to survive, and it gets "cleaner" and more "crystaline" way down low.
there's harmonics, compression, treble boosting, distorting... lotta shit going on!

fuzzfaces are weird!

[Mcentee2]

Hi, and thanks as well!

That would probably explain why a treble bleed on a strat also messes with the cleanup as it basically still let's through the full signal at the high end and  poss some.midrange as well depending on how it is set up.

I have a treble bleed on my strat with an on/off toggle so I can use it with FF properly, it also has a pot attached so I can tune it however I've never done that with a fuzz face yet to see if there is another set of happy places😀

[pinkjimiphoton]

if you REALLY wanna control your fuzzface, make one of your tone knobs a hi pass filter to cut the lows. then you can dial in ridiculously useful sounds from your guitar with a fuzzface

[Mcentee2]

Yes, that is what my treble bleed is effectively! Just tried and it works pretty well dialling  in whatever cleanup response I want! 

[pinkjimiphoton]

nope, a treble bleed is NOTHING like what i speak of. a treble bleed leaks highs around the varying load of the pot, so as you turn down, the tone stays the same, or similar.

i am talking about a variable high pass filter. totally different animal.

as you roll off the lows into a fuzzface, it becomes more of a VERY marshally overdrive instead of a fuzz.  a treble bleed can't do the same. its bleeding treble thru a volume pot, not rolling bass off the actual signal.




there's a bunch of ways to do it. the above will give ya the basic gist.

[Mcentee2]

 :icon_idea:Ah! Thankyou.

[j_flanders]

nope, a treble bleed is NOTHING like what i speak of

A treble bleed is the same thing as your bass cut.

There are many ways to wire the controls on a guitar but traditionally this is the way it's wired most of the times:


1)Volume control: is a typical voltage divider. (In independent wiring the volume pot is a rheostat. It will not clean up a Fuzz Face as there will be no series resistance when turning down. There may be other factors involved but the series resistance is a huge part)

2)Tone/treble control: is actually an impedance control or load control.
It's not an RC filter like we use in stompboxes or amps. It's not a voltage divider where one part is a capacitor.
It's a variable resistor that, when turned down, loads down the pickup, thereby lowering the resonance peak and reducing the treble content.
You can remove the cap on the tone pot and it will still work as before (until you reach the final part of the pot range, where the tone control changes from a resistive load into a capacitive load. The resonance peak will go up again but will be at a lower frequency, which is exactly what a capacitive load does to passive pickups.)

3)Bass cut control: contrary to the tone/treble control this is a typical RC filter like we use in stompboxes and amps. It's a voltage divider where one part is a capacitor.
You can make it variable by placing a variable resistance (pot) across the capacitor.
The resistor part of the RC is whatever resistance comes next and goes to ground: volume pot, tone pot or input impedance of first stompbox or amp. It can be unpredictable because of that. If you place it before the tone control you can actually also control the R part of this RC filter. Turning down the tone control then lowers the R in the RC bass cut filter and it will cut more bass.

4)Although you can wire a treble bleed in multiple ways, the most common way is a capacitor across the upper part of the volume pot/voltage divider, as in the image below. And that is exactly the way you wire a bass cut... So, they are in fact identical.
A 'minor' difference is that with a treble bleed, when you turn down the volume pot, you change the parallel resistance across the treble bleed cap at the same time as you change the bottom part of the voltage divider of the volume control.
If you wire the bass cut before the tone control you could do the same thing by turning down tone pot and bass cut pot at the same time.

[Mcentee2]

Honestly, thanks to both of you!

I did edit my last reply to quickly say I thought my treble bleed looked the same as that bass cut, but then edited to remove whilst I went away and looked at it again!

Mine is a fairly basic one with a cap across the volume in and wiper, however I have wired up the second 250k pot in parallel with the cap so as to tune it in live rather than go though endless testing and stick with a static parallel resistor.

The vol wiper then goes to the jack, the master tone is fed from the pickup switch out and in parallel with everything.

The pot and cap are on a toggle as well so I can easily turn it off for fuzz faces, although now I think I understand a little better it can be useful there too!

Having said all that, I do understand that my treble bleed only works at all if the volume pot is not at full😀 whereas a proper bass cut would affect the whole signal regardless of volume knob position.

[pinkjimiphoton]

you gotta try the bass cut control.
its a completely different animal than you expect
j is right, but wrong. the application may be "the same" but in use, there's a HUGE difference between a variable bass cut and a treble bleed. 

with the bass cut control added to the guitar, you can control the fuzz level FROM the guitar. full bass? full fuzz.

the diagram i posted is fine and easy, as its a q&d implementation that will work for any standard guitar without having to change pots and shit. swap a couple wires around, done deal.  the picture he posted isn't how its done "most of the time", as really.  practially nobody has uses these on commercially available guitars in years.

you don't "need" to use a 1 meg pot for the bass. shit, 10k is probably sufficient.  so the standard 250k or 500k pots will work fine.

the whole thing is ultimately in parallel with the volume control if ya really want it to work well. i tried every configuration of it i saw on the web, and realized ultimately the simplest way to go depends on your guitar and how you have it wired.

the easiest way is to wire it either in series <tho its all really parallel >  with the output from the switch, or the output of the volume, depending on your guitar.

most gibsons the output from the switch goes to the output jack. most fenders, it comes from the switch.

as shown in j's schematic too, the bass cuts as you turn the knob up, which is pretty maddening for any normal guitarist who immediately cranks every knob.  it makes more sense to wire it the other way, so as you turn it down, it cuts bass,rather than turning it UP to cut the bass. either way is fine, its just counterintuitive the so-called "stock" way.

what makes the bass cut different from the treble bleed circuit is the variable resistance in parallel with the cap in the bass cut, where as the treble bleed is shunting the signal to ground on a volume pot.

btw, removing the cap from a tone/treble pot doesn't "work the same"  it WILL change the tone somewhat, but without the cap, it doesn't "know" what frequencies to bleed. try it and get back to me. this is why different kinds of caps can have vastly different tonalities. not gonna get into the capacitance, esr, etc etc. don't need to.

look at the final picture posted of the treble bleed and the bass cut. are they doing the same thing? only sort of.  the bass cut <which again should be the mirror image of what's posted by j if ya don't wanna drive yourself crazy> is only working to attenuate low frequencies.

the bypassed volume pot is to attenuate ALL frequencies, with an emphasis on the bass. as you turn the guitar down, it gets brighter. the bass cut control does the same thing, but without the volume aspect really. same basic concept, but still, apples and oranges.

you get a better taper for the bass with just the wiper and  pin 3 connected than bridging the first half of the pot, too.  of course, ymmv.

not saying j is wrong, as we agree on 99% of this stuff.. just the application is different. i add this shit to literally every single guitar i own, so i know what works and what doesn't and the few caveats to the whole mess.

you can absolutely wire it as shown by either of us, and it will work, altho slightly differently. the dif is mine is literally just re-routing a couple wires and swapping out one cap rather than requiring a complete re-wiring of the guitar control cavity.
it will work on just about anything <you can even do a variant with one knob, tho its kinda weird>

the bass cut is most noticeable with fuzzes like the fuzz face. with overdrives/distortion etc it works, but not as well. fuzzes have a huge amount of bass to them, which gives the cut something to work with. you can control your tone from the one knob pretty much with a fuzzface.

i can't take credit for any of this shit anyways, i first read about it on joe gore's tonefiend site. his application was a bit different than mine, i just took what i learned there and @#$%ed with it til it worked as i needed it to.

trust me... it makes more sense to turn DOWN the bass on a bass cut that turn UP the bass cut to turn DOWN the bass. once ya try it in real time, it makes more sense.

also works better with humbuckers than single coils, or with single coils with 500k pots.  most of the bass cut happens in the first 10% or so of the pot rotation, so if ya wanted to change the pots, anything from about 10-500k is fine. 1 meg is fine too,  my 50's kay speed demon has the 1m bass cut pot, but it doesn't work in practice any different really than a 250 or 500k pot.

just my experiences in the real world. ya'll's mileage may vary and probably should


in summation, the treble bleed may "be" almost "the same thing" but in reality, two different <if related> applications.

with the variable bass, you can literally control the fuzz of the fuzzface.  with the treble bleed, as you turn the guitar down, it will clean up and get brighter. the combination of the two will allow you to make a les paul sound like a strat or tele or quasi rick.

so with both, you can set your volume wherever you prefer it, or roll it up and down for different tone and effect as i do, and use the bass to dial in the perfect amount of fuzz.

you gotta try it first. trust me.

[Mcentee2]

I'll have to give this a go, but am running out of space and positions for toggles and pots on my stray. I will prob change the treble bleed for bad cut and see which I prefer, I could poss get them wired with an on/off/on toggle as it could be just where the feed to it comes from.....hmmmmm.

However! I forgot the point of the thread was about why ff get brighter as guitar vol is turned down! And I think the above detour definitely helps explain, thanks again.

[pinkjimiphoton]

i may have come off as something of a dick, and if so, i apologize... j's post was freekin brilliant, and i know that *I* personally actually learned quite a bit from his explanations of things.

just apples and oranges... i forget who said it, but that which sounds good, is.

rock on gents

[Mcentee2]

Lol!

*If* you did come across as a dick, which you didn't, you have earned that right many times over on this forum!!

[Steben]

 A dick dale?

[j_flanders]

as you roll off the lows into a fuzzface, it becomes more of a VERY marshally overdrive instead of a fuzz.
it makes more sense to wire it the other way, so as you turn it down, it cuts bass

I agree 100%, not only for a fuzz face but most fuzzes, also Big Muffs for example.
(it's also the way I wire it btw, and how the schematics were meant to portray.)

For the rest I don't agree so much.

what makes the bass cut different from the treble bleed circuit is the variable resistance in parallel with the cap in the bass cut, where as the treble bleed is shunting the signal to ground on a volume pot.

With a treble bleed you also have variable resistance, namely the upper part of the volume pot / voltage divider:

the bass cut control does the same thing, but without the volume aspect really.

You may not notice or realize it, and how much you notice depends on the value of your bass cut pot and the next resistance to ground, but the volume aspect is there:

btw, removing the cap from a tone/treble pot doesn't "work the same"  it WILL change the tone somewhat, but without the cap, it doesn't "know" what frequencies to bleed. try it and get back to me. this is why different kinds of caps can have vastly different tonalities. not gonna get into the capacitance, esr, etc etc. don't need to.

As for the tone knob, you still speak of 'bleed'. There is no 'bleed' concept or aspect on a tone control on a guitar. I explained it above. It's not an RC filter. The output of the tone knob is not taken from the junction of the R and C. It's taken from the top of both. The tone knob changes the Q of the resonance peak. It loads down the passive pickup like a low(er) input impedance would. Completely different concept from a tone knob on a stompbox:

you gotta try the bass cut control.

I have it on my guitar(s). I love it.

[pinkjimiphoton]

you seems to assumes ol pinkstah has some kinah knowledge, like, or somethin'

just a monkey with a breadboard here bro

all i can say is the shit i do that works or don't.

i too gotta have a bass cut on everything. its crazy. but if it sounds good.........