"The NE5532 outperforms..." really?

[Phorhas]

So it's not Slew rates, OK... so what is it that makes the tonal differance?

what dose make some ICs better sounding, or maybe - better suited for our applicatons?

[StephenGiles]

But maybe you are forgetting the how perceived performance changes with the voltage applied to the power pins
Stephen

[Paul Marossy]

So it's not Slew rates, OK... so what is it that makes the tonal differance?

I think part of it is due to the different types of opamps - there's JFET, BJT, Butler front end, etc. On the scope, you can see small differences between the different types. Some people can hear it, too. But, as I said, they are small differences that I don't think most people (non-musician/average joe) can even hear.

[Ge_Whiz]

Lemme ask ya'll a hypothetical question.

Is a thoroughbred race horse of the finest breeding and training better than a Clydesdale (think of Budweiser beer wagon) draft horse?

Clearly, that depends on whether you're a gambler or a drinker! Me, I'd stick a Clydesdale in my TS-808.

[WGTP]

In my op amp analysis, I found that the diodes used for the distortion had a larger effect on the sound than the op amp.

I speculate that some of those mysterious things like impedance, frequency response, harmonic content of distortion produced, etc. all have to do with it.  Grit, Grain, Warmth, Headroom, etc.

My family noticed that the noise that was produced by some was less irritating than others.  

[Eb7+9]

So it's not Slew rates, OK... so what is it that makes the tonal differance?

what dose make some ICs better sounding, or maybe - better suited for our applicatons?

Harmonic distortion specs in high gain NFB systems, derived from steady state sinewave testing, are relatively irrelevant to dynamic behavior ...

In Miller integrating op-amps the Slew Rate comes as the product of the Compensation capacitor Cc and current Ib biasing the front-end diff pair ... V/s = Qc/s = Cc Q/s = Cc Ib ... basically it's an "amplitude-frequency product" limitation that lies way above our (very) roughly 1/4 volt / 15 khz or so needs, at least in theory ...

Op-amps are essentially an OTA with some kind of voltage buffer shielding an internal hi-Z/hi-gain node from the output load ... op-amps that are designed to source high-current (lowZ loads) typically have much larger devices in the output buffer and less emitter resistance consequently ... under high-current conditions this resistance can slow things down below theoretical Slew-Rate limits ...

This reasoning can be extrapolated to the situation of the op-amp driving non-linear loads like clipping diodes ... likely the reason why the hi-drive NE5532 gives good definition in the TS808 circuit ...

Lastly, it's worth remembering to play with the compensation capacitor - it can have an effect on perceived sound quality by introducing too much ringing on transients ...

take care  :!: ... jc

[Belanger]

Hope to goodness it wasn't me making such a claim about the chips in question.

The "slew thing" is truly misunderstood in this community.  Again, I'm not the expert EE here, but the relevance of the slew figure depends on the application, as is noted by many.  It is really, REALLY, hard for me to think of a context in which a slew rate of 8v/us would be critical to the functioning of an analog floor pedal, and really, REALLY, REALLY hard for me to imagine an instance where 22v/us would hold any audible advantage over 8v in the same category of applications.

The slew rate depicts how capable the device is of producing large scale voltage swings with great rapidity.  If you were looking for a 741 to be able to accurately reproduce 18khz waveforms while applying a gain of 200 at the same time, it ain't gonna happen.  Now if you asked it to reproduce the same waveform with a gain of 5, NOW we're talking, since a gain of 5 might imply a simple change between an input signal of 30mv and and output of 150mv.  Clearly the slew requirements aren't all the stringent.  As I noted in another thread, it is a common trick to distribute the gain of a circuit amongst several devices, such that the amount of voltage change each is tasked with is actually modest.  So, a trio of 741's each with a gain of 5 would yield a combined gain of 125, with none of them being asked to produce a particularly huge voltage swing.  Where more modern devices provide advantage is that all the required gain can be packed into a single device without having to pay a functional cost in terms of usable bandwidth

Typically, the occasions where required speed of voltage swing starts to become demanding in floor pedals is in, you guessed it, distortion units.  As it turns out, fortunately, thse things sound like crap when the bandwidth is too wide, so they tend to have a fairly restricted bandwidth.  This means that while the device might have to swing wide in terms of voltage, it won't be obliged to do so very quickly, making even a limited slew rate more than acceptable.

Now, if we were talking about a phono cartridge preamp in a high end system that is expected to deliver 40db or more of gain for a puny mag cartridge (or worse, moving coil) with at least 25khz bandwidth or more, slew rate WILL start to matter.  It is important to recognize when concepts imported from the audiophile literature are, and are not, pertinent.

In case it matters, though, buddy of mine makes some mic preamps with OP-275's and apparently they are absolutely killer.

I know this is a really old topic but I had to thank you for all of this info. I've just started out and I don't want to get pulled into to much of the widely believed myths out there of which there is so many. Really geat points you brought up and there's really no arguing facts lol

[Hatredman]

In this experiment, the guy replaced the TI4558 on a TubeScreamer TS808 clone for a number of other OpAmps: JRC4558, TLC2272, C4558 (which he called "Magic Mojo"),  LM833 and a TL072.

They all sounded exactly the same. Some guys noticed a slightly different tone with the last one, an NC14577, which is a VIDEO amplifier, but not that much too.

The OpAmp used in a guitar pedal, be it a overdrive/distortion or whatever, is irrelevant. How you EQ the signal is what matters. Mind your capacitors, kid, and let the chip do its thing alone.