big muff opamp version

[jasonsmusicgear]

Could someone tell me if the 330k resistor in the upper left hand corner should actually connect to pin 1 of the 4558 op-amp or pass over it?

Also this is my first attempt with ICs and I started to put in 2 4558s but then got to thinking that I should only use one.  Which way is correct?

Thanks

[The Tone God]

I would say it connects.

Andrew

[MikeH]

You are correct.  You only need one 4558 because it is a dual opamp.

[theehman]

Also this is my first attempt with ICs and I started to put in 2 4558s but then got to thinking that I should only use one.  Which way is correct?

Thanks

Just 1 4558 and 1 741.

[oldrocker]

I would use the schem below.  It worked better for me.  The logmoster pic below shows some edits that that I did and IMHO made it sound better to my ears. (Ignore the 4.7uF and the 47k to ground off of pin 1.)  A 33k in place of the 8.2k stopped some gating and too much oscillation.  But you be the judge.
http://gaussmarkov.net/layouts/opbmp/schem.png
http://www.logmonster.com/images/full/?pic=opampbm_1176959853-422-14999.jpg

How about Markm's layout?
http://aronnelson.com/gallery/album76/1977BigMuff_LAYOUT_001

[jasonsmusicgear]

Thanks for all the help guys, and for the extra schems that will help.

[oldrocker]

This is my favorite fuzz pedal hands down.  I had to mod a few things to get it to sound like I wanted but it was worth the effort.  I also built a stock transistor version and it's nice and raunchy.  But the op amp version I built on perf is the best.
I didn't see Mark's layout before hand so I just designed it as I built it.
http://www.logmonster.com/images/full/?pic=bm1_1177111339-422-15000.jpg
http://www.logmonster.com/images/full/?pic=bm5_1177050438-422-15001.jpg
http://www.logmonster.com/images/full/?pic=bm7_1177031332-422-15002.jpg

[tcobretti]

I guess I didn't see Mark's layout, so I also did a layout for this one, but haven't verified it yet.

[NoFi]

There are at least two different op amp circuits (i had two different original op amp big muffs at one point, with different layouts...).
The first schem posted by jasonsmusicgear is basically "correct", except for a few components values. For example the 82k before the 741 should be 8.2k ! And it's nice to have a pot instead of it !
I had posted some details and pictures of original circuits in a thread called "the opamp big muff corner" but now it looks like someone deleted it...
I still have the pedal, so i guess i can recheck every component for that blue schemo if someone wants me to do so. But the way the bypass is wired is just nonsense, it applies some gain even when in bypass lol.

[nightingale]

Hy NoFi?
I would really be psyched if you found the time to add corrections to the "blue and green" opamp muff schematic posted above.
I have built seven different BMP versions/variations, and I think the opamp version have become my favorite!

thanks in advance,
ry

[markm]

Hy NoFi?
I would really be psyched if you found the time to add corrections to the "blue and green" opamp muff schematic posted above.
I have built seven different BMP versions/variations, and I think the opamp version have become my favorite!

thanks in advance,
ry

That's interesting.
Seems most like the other but, the OpAmp circuit has been gaining popularity.

[jasonsmusicgear]

I finished this pedal last night and now have a few more questions.  I have never played through a big muff before so I'm not sure how they are supposed to sound but I don't think its working quite right.

The lower three strings sound great, they have a lot of very good sounding fuzz, but the top three strings sound very weak and they seem to oscillate in and out with a bit of static mixed in.  I think its picking up a bit of radio signal as well.

I used the schematic posted above and maybe the incorrect values as stated by NOFI are the culprit.  I think the schematic posted by old rocker has some of those corrected values and I will check that out.

A couple of other things that are happening:  The fuzz and tone pots don't do anything, I think the fuzz pot is just wide open.  The tone section does not have voltage anywhere.

Are there any suggestions of what to look for without knowing voltages yet. 

Thanks for all the help. 

[runmikeyrun]

I put a single 2N2222A transistor gain stage before the opamp and it seemed to really get it distorted, really high gain w/ the gain control at full up.  I like that pedal a lot, you can get it really midrangey and fuzzy or scooped mids metal sound with lots of gain.

[nightingale]

Hy NoFi?
I would really be psyched if you found the time to add corrections to the "blue and green" opamp muff schematic posted above.
I have built seven different BMP versions/variations, and I think the opamp version have become my favorite!

thanks in advance,
ry

That's interesting.
Seems most like the other but, the OpAmp circuit has been gaining popularity.

I think there is something different about the way it compresses that I prefer?
Around here it seems like the op amp muff has a darker tone.  I think that is slightly true, but the tone control on my build has more "usefull settings" than all of my other BMP clones.

I have all seven of my BMP builds boxed up.
When I  record song ideas in my little home studio, I usually grab two or three and start "tone tasting".
I have been consistently choosing the op amp muff over the others?

I am typically not an op amp guy. I prefer discrete builds. I prefer the having control over transistor selection.
For this op amp build I used a Burr Brown for the dual, but I doubt that has anything to do with it?

I guess I should mention that I play tele's through fender amps, or sometimes an 18watter.

hope this helps,
ry

[NoFi]

I'll try and check it out over the week end.

[petemoore]

For this op amp build I used a Burr Brown for the dual, but I doubt that has anything to do with it?
  Bound to have at least a very little something to do with 'it, probably less than with a dist+.
  Layout that uses all single oa's, then LM741's could be used.
  The times I've opted for 741's have all turned out good to better sounding than duals, hardly any difference in noise IME.
  They do great work in DIst+, phase 90 seems to have a 741 character with 741's in it..both are well behaved and near silent.
  'Hi fi' isn't always the most 'pleasant' solution, an opamp that 'slurs' a little bit can add character to the voice.
  741's arent' that bad, but just the lowliest, dirtiest opamp choice, but not even that dirty.
  Sometimes opamps are just too 'fast and forceful' to be pleasant.. a bit of 'clunkiness' or sluggishness can be a perfect compliment to od/etc....like you can hear the circuit while it's deciding what to do...teetering around a not so clearly defined edge.
  The 741 character is clear enough in DIST+ type circuits, not too sure it'd be so noticable in TS or BMP types.
  You tried a 4558 ?

[NoFi]

Well i checked the components, nothing spectacular.
- The 82k resistor before pin 2 of the 741 should be 8.2k
- The 47k resistor between the 62k and the 10k gain pot should be 47ohms.
- There is an additional 47ohms resistor between the +9Volts and the circuit.
That's all i could find.

[oldrocker]

Try the 33k resistor in place of the 8.2k.  That helped with the gated fuzz and oscillation in mine.

[NoFi]

I have a 10k pot in there, it allows for MORE oscillations and crazy levels of gain .
I guess i could change it for a 50k.

[petemoore]

  Seems strange.
Pin 3 [741] is pulled to ground at frequencies above whatever the .22uf cap to ground allows through to be shunted, [under the 741] which is a large part of the relevant spectrum I think.
  [I got 'dummy's OA BMP out, and decided to take a look at 'what from where' is on mine, what'd matter or not...] I found he put a 10uf there, and a 100k gainpot, they're about to get fixed...this gain pots wiring is part of what sets gain on the 2nd half of the 4558.
  Badly biased opamp sounds great in a bad way when 'driven to bias'...alone the pedal sounds rough/gated.
  I've got all the 'right' resistors [like *82k = 8k2] I measured.
  Pin 6 of the 741 is 4.69 of 8.46 battery..a result of the 820k/1m divider on it's + input I thnk...seems high but
  pin 3 is 4.36v - 3.27v [the voltage drifts while being measured, just like the -input, pin 2 does [pin2 measures from 3.27 - 4.36v].