op-amps with wide open-loop bandwidth ?

I don't intend to use them open-loop. What I hope to acheive is to gain an empirical understanding of what characteristics or specs make op-amps sound different in spite of the that the so-called expert theories as to why they shouldn't.

Thanks DM

Awfully presumptuous of you Phil. I am of no particular view at all other than collecting empirical data on my own and drawing my own conclusions. It has worked well for me over the years to do so. Perhaps this is why I am able to design solid-state guitar amps that are indiscernable from tube amps.

: > It was bunkum. : >

: > Many have since proved it was bunkum. : >

: > Matti was a troll. : : : As are most usenet self-styled experts...The OP is a good example of the : web educated product, totally confused. If the idiot has been dabbling : his life away with audio electronics piddling for the past 10 years and : yet cannot find the stamina to read through a simple text like Mancini's : OP Amps for Everyone, and Mancini means *everyone* regardless of : intellectual abilities, then let him go rot.

I'm currently custom designing a solid state guitar amp for one of the worlds foremost guitarist. If that's "going to rot", I'll take it. :

Thanks for an answer without a healthy dose of pseudo-intellectual one-upmanship thrown in for good measure :-)

DM

Thanks, I'll check them out. DM

:

: > I'm simply looking for a wide variety of op-amp types : > for sonic evaluation. IOW, I'm attempting to correlate : > what my ear hears with with the variations in specs : > from one op-amp to another and sadly deficient : > in the list of op-amps I've evaluated so far are any : > that are flat open-loop to 20Khz or higher. The best : > I have on hand are 10KHz. : >

: > So far my short list of star performers via the : > old golden ear test are; : > THS4022, THS4052, THS4062, THS4012, : > AD828, LT1363 : >

: > Although it should be mentioned that these are : > for guitar amplifiers and that Audio Hi-Fi enthusiasts : > might not agree about the merits of the afore mentioned. : : The whole idea of opamps is that, if they have enough extra gain to : throw away, at the frequencies you are interested in, then they all : act the same. But the definition of "enough extra gain" is highly : dependent on the circuit they are part of. In other words, if the : opamp is fast enough and has high enough gain, it disappears as a : source of sound color, and the other, more predictable components in : the circuit, program its output, almost completely. The effect of : gain on, say, a unity gain follower is very different than the effect : of gain on a distortion effect generator, at the same frequency. So, : before any suggestion is likely to help you, we need to understand a : lot more about what circuit you intend to use this opamp in. : : And since, it is fairly obvious that you are not yet a circuit : designer, you would probably get a more helpful response if you start : over in sci.electronics.basics : : Good luck.

Well John, that's all fine and well in the world of pseudo-intellectual EE-expertism, however in the real world of empirical eveidence, it don't pan out. There are op-amps with specs far exceeding your limited definition of what's necessary to 'dissappear the source of sound coloration' that sound entirely different in the same circuit and exhibit very different qualities of dynamics in the feel of a guitar when you're playing it.

I started out designing guitar amps over 20 years ago and quickly learned that the op-amps of the era couldn't compare with my discrete designs. I only recently started to look at op-amps again as a viable possibility due to recent advances in op-amp design.

I didn't ask for a lecture on tone. I asked for knowledge of any op-amps that have a flat open-loop response beyond 20KHz instead of the typical corner of 100Hz to 19Khz. The open-loop gain in V/mv I don't give a rats ass about other than that it's relatively flat to 20KHz or higher.

I realize that I didn't do a very good job of communicating my quest, but cut me some slack here. Ever since hurricane Katrina waxed my estate, I've been averaging 5-7 hours sleep per night sometimes even skipping sleep altogether in an effort to complete a very important project for a rather important person on schedule in spite of the hurricane induced setback.

I can't tell you about the circuit it's going to go in because it's not for any circuit in particular but rather for sonic evaluation for exacly the reason that in the work I do, sonic evaluation is the only thing that means diddly-poop. I've heard the theories of the "experts" on the subject of tone fall by the wayside over the years and watched rather bemusedly as they scramble to come up with new theories as to why the old theories didn't account for fact that people can hear the difference in circuits that so-called experts would logically conclude (according to the theory du juor) should be sonically indiscernable. IOW, the reason I want such an op-amp is to collect empircal data rather than rely on the opinion of self-proclaimed experts such as yourself that don't know near as much as they think they do. Now, if you want to rail on and hurl insults because I misinterpreted your question and gave a seemingly non-sequitur answer, do carry on.

DM

"Dave Moore"

** To you personally ?

Or * objectively * - as proved by a controlled "blind" test situation ?

** Go prove that objectively & make yourself very famous.

....... Phil

"Dave Moore"

** Yawn .......

We have ourselves a " live one ".

...... Phil

"Dave Moore"

** Not a single presumption was involved.

** Yawn .......

" It is a bad scientist who experiments on himself ...."

** Yawn .......

Exactly what every fake, kook and charlatan says.

** Yawn ........

Turned any lead into gold lately ??

........ Phil

"Dave Moore"

** The only op-amps that meet your superfluous criterion are intended for Radio Frequency ( RF) work and are quite ill-suited for general audio frequency applications.

However, a guitar amplifier is not a normal piece of audio gear.

It is a signal modification & " sound " creation device.

....... Phil

Then I suspect that the circuit is not well designed (is making demands on the opamp that do not allow the assumption of excess gain to apply). By the way, sorry if I underestimated your experience. The question just sounded like one from a newbie. I was sincerely trying to be helpful.

Like any component, there is some art in getting the expected performance form them. No audio circuit, especially one in an instrument amplifier should ever let the opamp output saturate, even under severe signal overload conditions. That is when you hear the opamp, as it struggles to recover closed loop operation and can do all sorts of strange and prolonged things. The feedback should keep the loop closed for any signal it can reasonable be expected that someone will put through the amp.

That is becoming clear.

You have my sympathy.

I'm interested. What are the test conditions for this test? Will the opamp output saturate during this test?

There are lots of poorly designed audio (especially instrument) amplifiers out there. The good ones sounds impressively similar.

Now, you are the one presuming. If you don't like the advice, you are guaranteed double the purchase price refunded.

I guessed wrong on your skill level and made what I hoped was a useful suggestion. People get lots of helpful hand holding on the basics group. The designers are more critical of each other, here, where they are more of a club.

Get over it, please.

Tut tut, that's no good. That's negative feedback via a different path. Clearly you're not taking your audiophile mystique seriously enough. And in any case, shouldn't you be using forced-air cooled class-A op-amps fixed to granite plinths?

--
Dave Farrance

No, what I suggested was loading an internal node to lower the low frequency, open loop, gain.

Also, I would never suggest forced-air cooling. It makes too much noise and the moving air causes the local speed of sound to vary. Liquid helium cooling is the way to go.

--
--
kensmith@rahul.net   forging knowledge

Oh dear...here we go again. Those golden ear boys with their "sonic transparency", I can hear a nat fart in the Australian bush whilst pissing off the Eiffel tower...

I have read you other posts mate, and, sadly your deluded. Its probably not your fault though. There is so much misinformation about on amp design its unreal.

Look, forget this open loop BW idea, it matters f'all, and has been done to death 20+ yewars ago. Its time to move on.

Kevin Aylward snipped-for-privacy@anasoft.co.uk

SuperSpice, a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design.

"There are none more ignorant and useless,than they that seek answers on their knees, with their eyes closed"

*Non-resonant* granite plinths. If you use the kind that have resonance somewhere in the range Fo -> Fmax, you have to dampen the resonance, which (obviously) requires water cooling. It gets worse, but I don't want to go there ... Ed

Try the LM386 - according to the data sheet it's flat to around 30 KHz.

** It is not even an op-amp.

** The negative feedback loop is internal to the chip.

....... Phil

That's the point...

googlegroups.com...

** You have no damn point.

Except the one on top of your head.

........ Phil