Opamp Big Muff corner

[Branimir]

Cheers!

Post your opamps BMPs here!

Here's mine:




PDF file with schematic, pcb and layout schem here

I tried both 4558 and TL072, and TL072 sound a bit more interesting me.. At least more harsh, dunno, there is no significant difference, but i prefer TL072...

in the tonestack i used 100nF instead of the 120nF (i didn't have that value), and i tried 47nf just to get rid of the scoop and the pedal doesn't sound much interesting with such flat freq.response, so i went back to 100nF, and i stay away from the treble position, i'm into the darker sounding part of the tone control.

Great pedal, and too bad the last topic got lost in the server move

[aron]

That's cool. I've never played an op amp Big Muff. Does it sound good? On paper it seems like it would.

[Branimir]

Hm, well, i'm no expert in fuzz pedals, but if i should describe the sound of it, here it is:

Since the coupling caps are high value, there's a lot of low frequencies coming in, the fuzz itself is not too harsh, i found the sweet spots around the middle of the po travel (of the tone control, of course). This is a higain pedal, palm mute is not chugga chugga as with distortion pedals (as expected), the tone is thick, as get to the treble side of the tone control, it gets "creamy", to the bass side of the tone control, tone gets much darker and that middle cut that this pedal has, does it's fair job at giving more treble edge to the boosted lows and lowmids (as some mids are cut with the tone stack).

I use a DIY orange clone (74' preamp with LTP phase inverter into 2xEL34 - 2x12" v30 oversized box), as I use the pedal and the amp, i would describe the tone as dark and heavy, with much harshness. I like it.

I have no clue how it sounds with other amps, but if should play with this pedal on some other amp, i would turn the mids way up on the amp, since the opamp BMP has that notch and its not wise to have a mid scooped sound

Dunno bout other types of music, but for lead, it's really really nice, much more thicker than any kind of distortion pedal (or even amp distortion), works excellent with neck pickups too, i play some sort of stoner rock and this pedal does that good.

Not a tough build and for higain pedal users, this is must.

[nelson]

Here is my opamp muff clone. I have a transistor muff too. I prefer the opamp muff. The transistor muff is just a different flavour, I would say more "creamy" as opposed to "fuzzy". I actually like the opamp muff for rhythm, I dont palm mute alot and like my chords to be loud fuzzy and sustain into feedback nicely. I had a problem with oscillation with this pedal but changing the input + output wires to shielded wire and grounding the input when bypassed solved it nicely. I tried all sorts of opamps in this pedal. I settled on a NE5532 for U1 and an OPA single for U2. Just seemed "nastier" which is what I was going for.

[Branimir]

Yeah, regarding sustain... it really sustains i found sometimes even too long to get ffedback out of single tone or chords, it just sustains and sustains..

nice heh.

[Branimir]

I settled on a NE5532 for U1 and an OPA single for U2. Just seemed "nastier" which is what I was going for.

NE5532 is a dual opamp, i see, but what is an OPA? Is this a typo or some kind of opamp i have no clue about

hehe..

You've put a bug in my ear now, i've gotta try the 5532!

Nastier you say?

[spock speach]  Intriguing .... [/spock speach]

[nelson]

OPA227

Texas instruments.

[Branimir]

How much difference does it make, compared to 741?

holy cow, i haven't put a socket for that one! .... grgrgrgrgrg

[ErikMiller]

As for the sound of different opamps, to my ears it makes such a huge difference that I still haven't found a current production dual or single that gives me the sound I want. They both make a difference. I truly wish it were otherwise because it would make my life easier. Each different brand of chip sounds different. And I've tried every current production 4558, 1458 and 741 I can get my hands on. The dual makes the biggest difference, but they both count.

Whenever I find the ones I like, I buy as many as I can.

A lower slew rate seems to actually sound better with this circuit, but for all I know there may be some other characteristic that creates the sound I like. I don't have a way to actually measure slew rate, but the older, more primitive chips seem to sound better. My guess is slew rate.

Cool that y'all figured it out; I was unsuccessful for a long time (research on the ICBM actually predates the introduction of the Crucible Si although the ICBM didn't come out until a year later) due to incorrect schematics, and finally got hold of an actual unit to reverse engineer.

[ErikMiller]

For heaven's sake, when you build one of these, socket both of the IC's, so you can swap different chips in and out. It's part of the fun!

[puretube]

A lower slew rate seems to actually sound better with this circuit, but for all I know there may be some other characteristic that creates the sound I like. I don't have a way to actually measure slew rate, but the older, more primitive chips seem to sound better. My guess is slew rate.

anybody took the nominal slewrates of various opamps into account
when comparing their "sound"?

the search-button offers quite a lot entries about "slew rate"...

one day, I want to find out, too... 

[Branimir]

This is mr. Mark Hammer's post regarding slew rate definition.. (post is from 2003)

There is an interesting thread about 741 opamps that i found in the archives, check it out here!

Maybe this is the time to open an another thread regarding slew rate and different brands/types of single or dual opamps!

[Branimir]

Dunno about the rest of you guys but i noticed lower output with this pedal than with some others... (when maxed out)

I know it's the compression of this muff that sounds different, than other distortion pedals, but i think there could be more output out of this unit...

Maybe i could put one transistor gain stage after the volume pot, similiar to the Rat design?

Or is there a way to get more output out of the last opamp? Guess not, without itroducing more distortion...

Any ideas?

[nelson]

Dunno about the rest of you guys but i noticed lower output with this pedal than with some others... (when maxed out)

I know it's the compression of this muff that sounds different, than other distortion pedals, but i think there could be more output out of this unit...

Maybe i could put one transistor gain stage after the volume pot, similiar to the Rat design?

Or is there a way to get more output out of the last opamp? Guess not, without itroducing more distortion...

Any ideas?

Mine has LOTS of output volume....even more so than my transistor muff which is almost up full volume....

[Branimir]

The thing is:

I used to use my modded DS2 as my main distortion, and the amp i have is non master volume, so i usually put the gain at low to have clean sounds (it's almost all clean amp) not loud, i would turn the level on my pedal all the way and when using the distortion i would usually have full power from the amp that way... (since level all the way on my pedal would compensate for the gain on the amp being turned low instead of almost full)

With opamp bmp, i noticed it's a bit quieter.

Testing head to head both these pedals, the ds2 had more output and the amp was louder..

i know it's silly, but i like to have distortion a lot louder than clean...



of course all this things wouldn't matter much if i played distortion all the way with gain on the amp really crancked

[ErikMiller]

I dunno, but the ICBM Fuzz can raise your signal a LOT.

Go back through your tone stack and volume control connections and make sure you have it right.

[Branimir]

I think it's okay, i get lots of output but i can hear the difference volume wise between ICBM and my DS2... not much, but i can hear it...
Maybe it's because of the middles.. DS2 has more mids... muff is kinda scooped a bit...

Nah, this is just me searching for problems where there are none... ignore me!

I simply love this pedal! Great powerchords, leads are really thick, can't believe this was in production in 1977! Heavy stuff heh...

[nelson]

Here is the guts of another muff I am making. This one is in trade for a Whammy reissue.

[Branimir]

I see you have a switch for diodes... How do led's sounds comapred to the Si ones that are stock?

I know how they sounds in some other distortion circuits, but here, hm... the fuzz iz already rumbly... so...

this is a "bb" box right?

cheers!

ps: i tried the pedal with a bass guitar and it sounds good, you could easily get rid of the guitar player in the band with this fuzz on bass Lows don't get lost and it's rumbly and fuzzy... two thumbs up... I still need to build a Rat to hear if it sounds better for bass guitar...
pps: bass guitar is some retro type, dunno what, musicman cheap copy, one pickup, similiar to the precision bass, so this should not be a reference for metal bass players..
stoner all the way.. hehe

[nelson]

Hi Branimir.

Bearing in mind this is after 3/4's a bottle of ouzo and I am workign on what I remember of playing it earlier.


The LED's have a certain "crunch". There is no other way of describing it. The silicon diodes offer a constant harmonic rich sustained fuzz whereas the LED's offer you a higher clipping threshhold and a "crunch". I find it just another texture and it made me change the dynamics of my playing to get a decent response. The guy wanted germanium diodes too but I really didnt want to wire up a rotary switch.

I am going to eventually breadboard diode and opamp experiments for this one. I am also eventually going to severely tweak the tonestack.....


All in good time.

Although as someone said to me once. "Alot hasnt changed in the fuzz since the 70's"

I am inclined to concur.