LM741, Why the bad rap?????

[markm]

don't be afraid to try the "stock" version of a pedal before you go into mod-land. at least that way you know what your modding, and you may just find you don't need to mod at all...

Amen to that.
I've built more than a few circuits that sounded fantastic in the stock form only to sound like crap modded.
Mods aren't always "good".
There's and old saying that goes;
"One man's garbage is another man's Gold"
Of course, the other old saying that comes to mind is;
"You can't make chicken salad out of chicken sh*t!"
I'm done now.......thank you!

[phaeton]

In the case of the OD250 and Dist+, users who though they might be able to score a two-fer-one by installing a diode-lift switch were surprised to find that the thing distorted even without diodes.  So, even though it doesn't look like a double clipper on paper, in reality it sort of was - what you feed to the diodes is already clipped.

Well that explains a lot, heh.  I was fiddling with a 741 awhile back and I couldn't get it to clean up.  I checked bias, this that, and the other thing, but it distorted no matter what.

I guess it's kinda like the 386 in that you can't expect a ton of cleanliness out of it.


I guess the other thing to note about the 741, is that the design is freaking ancient.  Isn't it like the 2nd opamp ever made?

[stumper1]

"One man's garbage is another man's Gold"
Of course, the other old saying that comes to mind is;
"You can't make chicken salad out of chicken sh*t!"

As my Grandfather used to say,
"You can polish a turd all day long - and IF you're really, really, really lucky - you just might end up with shiney sh*t"

And I agree,  spoons DO rock!

[Joe Kramer]

Build a phaser with one  [741]  and I can pretty much guarantee you'll diss it.   

I've built several phasers with 741s (4741s in fact) and they sound delightful IMHO.

[petemoore]

  After trying diode to ground clippers using non741 opamps, like TL082/072 etc.
  I figure that the sound compression/distortion of clipping diodes is 'one thing' and tends to sound a bit 'sterile' probably because it's just a ceiling being put on a waveform.
  With the 741 in there the sound becomes more complex, probably because...and I say probably cause I'm just type/ramblin here...the 741 has a tough time replicating exactly the higher amplitude transients of input signal, shaping the EQ with every attack, adding 'anomolies' that for HiFi would be a bane, but for distortion adds 'character' or 'dynamic' or some other '1/2way descriptive' terms.

[Aharon]

This is a bit like saying "Everyone keeps going on about how great knives and forks are, and how lousy and dull spoons are.  Well, I tried eating my cereal this morning with a knife and fork, and let me tell you the spoon kicked their asses around the block and back!  Spoons rock!"

The OD250 and Dist+ are essentially designed around the 741.  No small wonder it sounds fine in there.  Not a whole lot of other applications where it will sound better than other contenders, though.  Build a phaser with one and I can pretty much guarantee you'll diss it. Build a compressor with one, and you'll be screaming "Who do I have to sleep with to get this thing out of here!". 

And then you have chopsticks................................

[Peter Snowberg]

And I agree,  spoons DO rock!

Witness Artis the Spoonman: (same guy the Soundgarden song is about)

One heck of a nice guy and he absolutely rocks!

[phaeton]

Does he have any N.O.S. teak in those spoons, or is it all JRC4558D?

[Dave Eason]

it's all about slew rates and so on right?  Like the 741 has a really low slew rate giving it its characteristics etc

[markm]

I think so.
I'd bet it's like the LM308 and it's slew rate is the reason the Rat sounds like it does.
At least, in theory.
I have no first hand experience to share about the Rat.

[Mark Hammer]

it's all about slew rates and so on right?  Like the 741 has a really low slew rate giving it its characteristics etc

Not exactly.  Slew rate is a measure of how quickly the voltage can swing.  Think of it like the 100 metre event for chips: how fast can you sprint?  But it is also a measure of usable bandwidth as well.  Most chips, if the gain demands imposed on them are modest, have way more than enough usable bandwidth for any audio purpose you'd care to mention.  As the gain of the circuit goes up, however, the amount of usable bandwidth goes down.  As if the chip is saying "Well, buddy, I can run THAT fast for about THAT distance, but after that, I'm likely to be too pooped to continue."  So, the more gain you aim for, which is tantamount to saying the bigger a voltage swing you ask the chip to engage in, the smaller a portion of the measurable spectrum it will be able to do that for.

In most instances, 0.5 to 1v/usec provides as much slew rate as we here would need from an op-amp for our guitar-related needs.  Anything more than 2v/usec is just gilding the lily (an English expression for taking something already perfect and trying to make it seem better).  The Rat represents a special case, however, where the gain is so excessive (several thousand at max gain setting), that the slew rate limitations of the chip, both naturally and altered by the 30pf compensation cap, make it do some strange things.  To the best of my knowledge, there are no 741-based circuits that aim for the same sort of weirdness.

[Paul Perry (Frostwave)]

, where the gain is so excessive (several thousand at max gain setting), that the slew rate limitations of the chip, both naturally and altered by the 30pf compensation cap, make it do some strange things. 

Here's a good bit of news.. you can easily get adjustable caps fro 30pf! Go for it guys!
(in fact there are ones from pocket transistor radios that go like 5 to 250 pf or so, quite small).

[MartyMart]

I've never tried an "adjustable" cap .... seems like a fine idea and would userp any socketed "cap swopping"
too
Can you get say 1n to 15n adjustable ?

MM.

[zachary vex]

741s are also a teensy bit current-hungry (for a single op-amp device.)

[Toney]

Here's a good bit of news.. you can easily get adjustable caps fro 30pf! Go for it guys!
(in fact there are ones from pocket transistor radios that go like 5 to 250 pf or so, quite small).

Outstanding call Paul.

The RAT I keep meaning to build just got an extra knob.
Adjustable compensation cap, nice.

[Seljer]

I was messing around with my RAT and took out the clipping diodes and noticed: that the sound is allready a bit distorted without them

is this the opamp (I think that I measured the bias voltage at the input of the opamp as 1/4 of the battery instead of 1/2 too, on both of the Rats I have made) breaking up or was it just my amps clean channel breaking up under all the gain?

[JHS]

ICs are not good or bad, the challenge is to find the right IC for a given circuit or design. The OD-250 and some other FX are designed around the 741 and the values are taken from the sample circuits in the datasheet. The 741 or 4558D are  very nice sounding ICs for OD or distortion FX, but I would not use them in HiFi stuff.

You can put any 308 subtitute in a RAT, there will only a minor difference in the sound, same in the Moongoose.
Landgraff uses a 100p as compensation cap in his RAT clone, but I can't hear a big difference between 30p or 100p.

IBZ's Fat Cat has the same sound as the RAT and has a 5534 w much higher slew rate in it with a slightly altered input circuit.

JHS

[WGTP]

I think the Dist +/Rat type circuits should be conceptualized as 2 stage distortions.  As the signal/gain increases the clipping diodes distort first, and then the op amp gets into the act at higher settings.  At lower distortion levels, there may not be as much difference (when the op amp isn't driven beyond it's design capabilities) between op amps, since the diodes are doing most of the distorting (the diode configuration should provide most of the distortion character).  As the distortion increases, the op amp contibutes a larger percertage of the distortion.   

When tweaking my old PV Special which has a similar distortion set up, the 4558 sounded good, but the OP275 had more clarity and detail and didn't get as garbled under heavy distortion, so ...   

[petemoore]

I think the Dist +/Rat type circuits should be conceptualized as 2 stage distortiongs.
  The 741 seems clearly to do a great job compared to 'higher performance' chips for getting 'first and second' stage distortions in the Dist+. A very noticable, different flavor, more complex.

[phaeton]

Not exactly.  Slew rate is a measure of how quickly the voltage can swing.  Think of it like the 100 metre event for chips: how fast can you sprint?  But it is also a measure of usable bandwidth as well.

Thanks for that analogy.  I am now enlightened.

The Rat represents a special case, however, where the gain is so excessive (several thousand at max gain setting), that the slew rate limitations of the chip, both naturally and altered by the 30pf compensation cap, make it do some strange things.  To the best of my knowledge, there are no 741-based circuits that aim for the same sort of weirdness.

Do you think someone intimately knew the 741 and its characteristics, and dreamed up in their head "hey, i'm going to do this and this to really torture that thing and it'll pull out these bizarre slew rate artifacts", or do you think they stumbled upon it by accident and decided it was a keeper?