Any good sounding Op-amp for high gain distortion?

[Mark Hammer]

+1 on the cheap bright orange cheese.  Love that stuff! 

I just need to find a way to keep the cheap, bright orange cheesiness of the 741 from making a mess of everything near it.  Maybe a g(r)ated effect of some kind, or perhaps using it in a LFO. 


EDIT: From a brief amount of research, I apparently owe it to myself to build an MXR Distortion Plus.

It's an OK pedal, but it makes a lot of folks happy.  Most of what is annoying about a 741 will be taken care of when you roll off the treble to keep the fizz out.  In other words, yes, its noisy, but the filtering needed to optimize the tone is going to remove most of the audible hiss.

[thermionix]

EDIT: From a brief amount of research, I apparently owe it to myself to build an MXR Distortion Plus.

Currently on my BB sits a gray-spec OD-250, sounds cool, I plan on actually building it.  I used half of a 1458, been wondering if it's worth the few cents to get a 741 and go full-on "correct" with it.  I have to order an enclosure, pots and a footswitch anyway, so I might.  Haven't tried the D+ yet, but I will in the next few days.  My guess though is that I won't prefer the Ge clippers, this 250 doesn't seem to want any additional mushiness.

No idea if there's a sonic difference between a 741 and a 1458 in these circuits, surely very small if any.  Analogman seems to think the 1458 has a bit more hiss.  Dunno.  But yeah, I guess my point is, I'm new to the 250/D+ experience myself, but I'm impressed.  Sounds pretty refined for such a simple circuit.  Try it out for sure, takes just a few minutes to BB it.

[stonerbox]

Why in gods name would he blend test with 40-50% clean? It really makes no sense if you what to study the sound of the opamp in detail. It's like looking at the details of a painting from 30 feet away instead of 15 feet.

[anotherjim]

Dual & Quad versions can differ in sharing supply/bias networks. You would expect it would be done in a way that doesn't change specs compared to the Single, but read the fine print in the data! That said, I'd think it matters more that you have good supply decoupling close to the power pins to avoid interaction between the amps - assuming more than one in the package is in use. Of course, the unused ones must also be tied off as unity buffers as per best practice.

The LM747 is a "true" dual 741 in that each half has the offset null pins, and this is a headline from the datasheet...

The LM747 is a general purpose dual operational amplifier. The two amplifiers share a common bias network and power supply leads. Otherwise, their operation is completely independent.

And the 1458, also dual 741 but without offset pins...

The LM1458 and the LM1558 are general purpose dual operational amplifiers. The two amplifiers share a common bias network and power supply leads. Otherwise, their operation is completely independent.

[Mark Hammer]

EDIT: From a brief amount of research, I apparently owe it to myself to build an MXR Distortion Plus.

Currently on my BB sits a gray-spec OD-250, sounds cool, I plan on actually building it.  I used half of a 1458, been wondering if it's worth the few cents to get a 741 and go full-on "correct" with it.  I have to order an enclosure, pots and a footswitch anyway, so I might.  Haven't tried the D+ yet, but I will in the next few days.  My guess though is that I won't prefer the Ge clippers, this 250 doesn't seem to want any additional mushiness.

No idea if there's a sonic difference between a 741 and a 1458 in these circuits, surely very small if any.  Analogman seems to think the 1458 has a bit more hiss.  Dunno.  But yeah, I guess my point is, I'm new to the 250/D+ experience myself, but I'm impressed.  Sounds pretty refined for such a simple circuit.  Try it out for sure, takes just a few minutes to BB it.

The essential difference between the D+ and 250 is the clipping diodes used.  D+ uses germanium, which will have a lower clipping threshold, hence more clipping at identical gain settings and hence less output.  The 250 won't clip quite as much, but the hotter output level will push the amp harder.  Depending on how much of your preferred level of grind comes from your amp or your pedal or the interaction of both, I can see where a person would prefer the D+ or the 250.  An optimal arrangement might be a string of diodes to ground and appropriate toggle wiring to achieve the two sorts of outcomes.  So, for instance, a back-to-back pair of Ge, in series with two back-to-back pairs of Schottky type (e.g., BAT46, 1N5817), and a 3-position toggle would yield the functional equivalent of the D+, the 250, and something in between.

[Agung Kurniawan]

Anyone here have a good e-book or link to read about opamp? I want to learn about opamp more deeper

[EBK]

Anyone here have a good e-book or link to read about opamp? I want to learn about opamp more deeper

Search Google for a PDF of Op Amps for Everyone.  400+ pages of good stuff. 

[pinkjimiphoton]

to my ear, they all sound the same. expensive, cheap. the biggest factor for me is noise.
i tend to like 5532/34's (single or dual) a lot and use them, but mainly cuz an engineer friend gave me a big sack of 'em.

my best advice is socket and plug 'em in til ya like them.

the peripherals around them matter far more.

like... i built a rat the other day. first one. never got to it. i tried good chips, i tried bad chips, i tried the correct chip, the lm308 even.
didn't matter, still sounded like a freekin rat to me.
in the end i went with an lm301 in the mojo style (the round case ic) just cuz it had a little less hiss to it, but really, a 741 sounded just as good.
tlo61/71 didn't really change the tone for the better. 

same thing with dual or quad  op amps. the only real diff i've noticed is in the background noise. and that tends to vary from circuit to circuit.

so i'd say its more important to use flameproof resistors... less his and crackle than carbon comps
and if ya need low noise, i just use cheap chicklets for caps, or general, i just use ceramic.

the best sounding of the dirt boxes i've built were built with the cheapest crap. seriously. i built a klon with nothing but ceramics and electros and that thing sounded better than all the others.
the colorsound diphonizer (madbean's honey dripper ) same thing. ceramic sounded better.

so don't get too hung on components. use sockets and your ears.

[reddesert]

I think most of the time spent worrying about mojo differences between op-amps would be better spent reading a good introduction to the op-amp, like the op-amp chapter in Horowitz and Hill's "Art of Electronics." (You can now get a used copy of the 1st edition cheaply on Amazon, at least in the US. Bonus - because the 1st ed is old, it lists some old parts like the LM308 and 741 in its table of op-amp specs!) A quote from that chapter:

Operational amplifiers have enormous voltage gain, and they are never used without feedback. Think of an op-amp as fodder for feedback. The open-loop gain is so high that, for any reasonable closed-loop gain, the characteristics depend only on the feedback network. Of course, at some level of scrutiny this generalization must fail.

As H&H allude, there are differences between op-amps, but they have to do with things like input impedance, bias current, and noise, that might make one type of op-amp work better in a circuit, but they aren't likely to produce mojo differences in tone. I don't know whether to find it amusing or bothersome that the idea of op amp mojo has gotten so much traction. To first order, the op-amp is a black box that does one thing very well (drive its two inputs to the same voltage), and the feedback network of the op-amp is what controls the circuit behavior.

[thermionix]

EDIT: From a brief amount of research, I apparently owe it to myself to build an MXR Distortion Plus.

Currently on my BB sits a gray-spec OD-250, sounds cool, I plan on actually building it.  I used half of a 1458, been wondering if it's worth the few cents to get a 741 and go full-on "correct" with it.  I have to order an enclosure, pots and a footswitch anyway, so I might.  Haven't tried the D+ yet, but I will in the next few days.  My guess though is that I won't prefer the Ge clippers, this 250 doesn't seem to want any additional mushiness.

No idea if there's a sonic difference between a 741 and a 1458 in these circuits, surely very small if any.  Analogman seems to think the 1458 has a bit more hiss.  Dunno.  But yeah, I guess my point is, I'm new to the 250/D+ experience myself, but I'm impressed.  Sounds pretty refined for such a simple circuit.  Try it out for sure, takes just a few minutes to BB it.

The essential difference between the D+ and 250 is the clipping diodes used.  D+ uses germanium, which will have a lower clipping threshold, hence more clipping at identical gain settings and hence less output.  The 250 won't clip quite as much, but the hotter output level will push the amp harder.  Depending on how much of your preferred level of grind comes from your amp or your pedal or the interaction of both, I can see where a person would prefer the D+ or the 250.  An optimal arrangement might be a string of diodes to ground and appropriate toggle wiring to achieve the two sorts of outcomes.  So, for instance, a back-to-back pair of Ge, in series with two back-to-back pairs of Schottky type (e.g., BAT46, 1N5817), and a 3-position toggle would yield the functional equivalent of the D+, the 250, and something in between.

Just to update this parallel aside, I tried Ge clippers in my 250 breadboard project, didn't care for them.  Sound got really trashy, splatty.  Yes more gain but a difference in tone too.  I'll go back to the 1N914s.

YMMV, yadda yadda yadda.

[amptramp]

Anyone trying to get distortion from an op amp should realize that op amps are characterized for linear operation.  All of their spec characteristics are defined for linear operation.  If you are trying to push the signal level beyond the common-mode input range, different op amps will have different characteristics, for example, the LF356 will go hard over to a rail if pushed outside of the common-mode range.

For an LF356, exceeding the negative common-mode limit on either input will force the output to a high state, potentially causing a reversal of phase to the output. Exceeding the negative common-mode limit on both inputs will force the amplifier output to a high state. In neither case does a latch occur since raising the input back within the common-mode range again puts the input stage and thus the amplifier in a normal operating mode.  This would make for an unpleasant non-musical distortion.

Exceeding the positive common-mode limit on a single input will not change the phase of the output however, if both inputs exceed the limit, the output of the amplifier will be forced to a high state.

The most important thing is that the unspecified characteristics of an op amp are not defined and therefore, they could be different for different manufacturers or even different factories.  I had 15 Fairchild µA2240 devices at one time but some were Korean and some Malaysian.  One national source worked, the other didn't in a circuit for an octave generator for an organ.  The device is a 555-type oscillator connected internally to an 8-bit counter/divider with open-collector outputs (a very useful device as an octave generator or a sequencer).  This is a largely digital part.  How much more susceptible would a completely analog part be?

A more typical situation would be using a µA741 as an output buffer for a distortion.  A 741 has such low open-loop gain at high audio frequencies that it would sound "warm" because it would eliminate the high-frequency "fizz" that comes from added distortion for any gain of about 5 or more.  But some 741's may be better than others for gain, so the sound would be different.

I am in favour of using devices within published characteristics such that any device from any manufacturer could be substituted without a change in sound and without temperature sensitivity.  Anything else is not suited for production.

[Agung Kurniawan]

Where do you guys study about op amp or any IC?
University? High school?

[EBK]

Where do you guys study about op amp or any IC?
University? High school?

I had some exposure to op amps during high school through independent tinkering, but I really learned most of what I know about op amps in college, mainly in my Sophomore year introduction to circuits course (while in pursuit of an electrical engineering degree).  I remember thinking of op amps as quite magical due to their relative simplicity and amazing versatility.  20 years later, I still like to think of them as magical. 

[bluebunny]

Where do you guys study about op amp or any IC?
University? High school?

diystompboxes.com