How do you remove the fizzle in an opamp Muff Fuzz?

[LucifersTrip]

I started going through some flawed early builds to try to correct them. I built this to spec and it does get a decent Muff sound:



...except that I get a fizzle/sizzle as each note decays [both chords and single note]. The strings seem to be a bit more sensitive than I'd expect...similar to when you use
a transistor that's too high gain.

I can almost always remove annoying wails and screeches in common 2-3 transistor fuzzes with strategically placed caps, but I'm not sure where to start on this one (I rarely use opamps)....or is it simply the nature of the 4558. Is there a quieter alternative...

thanx

[Chugs]

You could try placing small caps across pins 6 and 7 as well as pins 1 and 2 of the opamp. Start with 100pf caps maybe.

[jasperoosthoek]

Unfortunately I can only see the left part of the circuit on my mobile phone.

I would replace opamps with CD4049/69 inverters. The schematic will look similar. Run Off Groove has a lot of inverter circuits. You can safely replace opamps with inverters if the non-inverting input of the opamp is connected to half the supply voltage. The inverter input will be the inverting opamp input. The biggest difference is that opamps have much more gain.

You can try a bunch of things to make the opamp less fizzy. The mere fact that changing opamps has an influence on how these circuits sound proves to me that  opamps are not working as they should. Traditionally the idea is that opamps have so much gain that differences between units are made as small as possible. I made a fizzless tubescreamer with inverters (UBE Screamer from ROG). IMHO it sounds so much better.

So try inverters, the difference is huge.

[slacker]

Try putting something like a 1Meg resistor in parallel with the clipping diodes.

[LucifersTrip]

You could try placing small caps across pins 6 and 7 as well as pins 1 and 2 of the opamp. Start with 100pf caps maybe.

Just got done trying that...no luck using as high as .001uf

thanx for the suggestion

[LucifersTrip]

Unfortunately I can only see the left part of the circuit on my mobile phone.

Here's a small version:

I would replace opamps with CD4049/69 inverters. The schematic will look similar. Run Off Groove has a lot of inverter circuits. You can safely replace opamps with inverters if the non-inverting input of the opamp is connected to half the supply voltage. The inverter input will be the inverting opamp input. The biggest difference is that opamps have much more gain.

You can try a bunch of things to make the opamp less fizzy. The mere fact that changing opamps has an influence on how these circuits sound proves to me that  opamps are not working as they should. Traditionally the idea is that opamps have so much gain that differences between units are made as small as possible. I made a fizzless tubescreamer with inverters (UBE Screamer from ROG). IMHO it sounds so much better.

So try inverters, the difference is huge.

The 4558 is soldered in tight, but I'll consider the CD4049/69 inverters for the next time I try this.

thanx

[LucifersTrip]

Try putting something like a 1Meg resistor in parallel with the clipping diodes.

I just tried that. 1Meg didn't work so I slowly lowered the resistance. The sizzle actually  disappears when I got down to 1.85K
The downside is there's a little fuzz gone and there is some added hiss/hum (the type that my kitchen light causes in some of my other pedals)....though, not bad at all. I think I'll try some caps to remove the hiss/hum.

thanx for the suggestion

[Gus]

A circuit I like that is based from the muff fuzz like in this thread and ultra fuzz etc type circuits with a tone control.  Don't be fooled by my hand drawn schematic, this is a fun circuit.

http://www.aronnelson.com/gallery/main.php/v/gus/sickbass.GIF.html

Good starting points
.0047uf/470K, bass (yes .0047uf there is a reason)
.01uf/470K to 1meg, guitar
LF353

S1 and S2 allow the 2nd stage to run like a
comparator both open
diode clipping with gain control both closed
Opamp clipping with gain control S1 closed S2 open
and S1 open S2 closed, diode clipping max gain

[LucifersTrip]

A circuit I like that is based from the muff fuzz like in this thread and ultra fuzz etc type circuits with a tone control.  Don't be fooled by my hand drawn schematic, this is a fun circuit.

http://www.aronnelson.com/gallery/main.php/v/gus/sickbass.GIF.html

Good starting points
.0047uf/470K, bass (yes .0047uf there is a reason)
.01uf/470K to 1meg, guitar
LF353

S1 and S2 allow the 2nd stage to run like a
comparator both open
diode clipping with gain control both closed
Opamp clipping with gain control S1 closed S2 open
and S1 open S2 closed, diode clipping max gain

I'll keep that schematic on hand for possible future.

Do you also get hiss/hum like I do when S1 is open or when the parallel 1meg is raised ?

thanx

[tubelectron]

Hi LucifersTrip,

I am surprised that the treble taming caps didn't remove the fizzy decay. But it is often a sign of auto-oscillation, so tame the gain a bit (220-470K // to diodes), insert a higher serial resistor than 10K for IC2, try a 1n cap from 1 to gnd... Or may be it's a coupling by wiring ? It sometimes arises... You should make it work at the end !

Personnally, I prefered the transistor version, in a modified way, as follow. No hum, no hiss, no fizz, certainly less gain, overdrive-styled but good-sounding if you play quite loud...

[LucifersTrip]

Hi LucifersTrip,

I am surprised that the treble taming caps didn't remove the fizzy decay. But it is often a sign of auto-oscillation, so tame the gain a bit (220-470K // to diodes), insert a higher serial resistor than 10K for IC2,

I actually have a 100k pot there. Raising the resistance did nothing to stop the fizz.

try a 1n cap from 1 to gnd...

...just tried..unfortunately no change.

Or may be it's a coupling by wiring ? It sometimes arises... You should make it work at the end !

It seems that a small resistor parallel to the diodes is the best solution so far. I tried it again & this time the fizz disappeared at 3.75K
instead of the 1.85K before.  It adds a little hum/buzz, which I'm working on removing now.

Personnally, I prefered the transistor version, in a modified way, as follow. No hum, no hiss, no fizz, certainly less gain, overdrive-styled but good-sounding if you play quite loud...

Yes, I prefer the transistor version also. I just made so many different 2-3 tran fuzzes I wanted something different.
I saved this schematic, which is very similar to yours:


thanx for all the suggestions

[tubelectron]

Hi LucifersTrip,

Hi LucifersTrip,

I am surprised that the treble taming caps didn't remove the fizzy decay. But it is often a sign of auto-oscillation, so tame the gain a bit (220-470K // to diodes), insert a higher serial resistor than 10K for IC2,


I actually have a 100k pot there. Raising the resistance did nothing to stop the fizz.


Quote
try a 1n cap from 1 to gnd...


...just tried..unfortunately no change.


Quote
Or may be it's a coupling by wiring ? It sometimes arises... You should make it work at the end !


It seems that a small resistor parallel to the diodes is the best solution so far. I tried it again & this time the fizz disappeared at 3.75K
instead of the 1.85K before.  It adds a little hum/buzz, which I'm working on removing now.

Indeed there's something wrong in the behaviour of your muff-fuzz trial, a bug somewhere... For sure, you shouldn't be annoyed like that.
To help, here is the schematic of my Doctor FUZZ, which is very similar in the principle to the Muff-Fuzz OpAmp version, with even an increased gain, but no fizz (neat decay) nor hum (when guitar volume shut down) nor oscillation...



A+!

[Gus]

This type circuit is more sensitive to the opamp used because of its design.  I tend to like NS lf353s.
Look close at the link I posted
All the values are picked for reasons and you have a nice tone control, gate/threshold control, and adjustments on the higher gain 2nd stage.
Sometimes it is about how you adjust the gain of the stages

[Gus]

https://www.diystompboxes.com/smfforum/index.php?topic=123951.0

[j_flanders]

I built this to spec and it does get a decent Muff sound
...except that I get a fizzle/sizzle as each note decays [both chords and single note].

You get (or rather got, back in 2010) that decay because the schematic is missing a resistor in the NFB of second opamp, parallel to the clipping diodes.
The schematic was probably drawn (and also copied thereafter) from an old ehx Muff fuzz that was missing some components. The complete ones I've seen, do have a resistor there.
There are two threads where I posted a lot of photos with gutshots of complete opamp muff fuzzes.

[Mark Hammer]

The "problem" really stems from the absence of a feedback resistor in stage 2.  Bear in mind that, in the absence of any other negative feedback, stage 2 is "persuaded" to shoot for the open-loop gain of the chip, until the diodes begin conducting, at which point it behaves more or less like a Tube Screamer...for a moment.  The fizz you are hearing is really the impact of ripple in the signal, that falls above and below the conduction threshold of the diodes at an audio frequency.

Look at Pinkjimiphoton's thread today (and Jack Orman's responses) for an example of how the same general circuit should be done.  The Muff Fuzz circuit, as drawn, has a gain of 5x in the first stage, Jimi/Jack's introduces more gain in the first stage, that brings the signal up closer to the forward voltage of the diodes in the second stage, and also includes a feedback cap to remove some of the artifacts of crossing the conduction threshold back and forth.  It's a better version of essentially the same circuit.

I've made/modded several of the discrete transistor versions, including a modded clone of the Double Muff.  I think it is a better-sounding circuit, and quite amenable to many useful tone-shaping mods.  Stock, it is essentially a fixed-gain silicon Fuzz Face.