I overdrove my op amp, yuck!

[DrFrankenstein]

Just thought I'd toss this out there for the heck of it.
I had a pretty basic dual op amp circuit I built and started toying with like doctor Frankenstein. I ended up overdriving it with an older preamp I built due to the lack of output.

And now I know why I've always heard op amps sound like garbage when you overdrive them. They can make beautiful distortion which you can overdrive externally but the op amp itself...yuck
I even tried cleaning it up with various caps and resistors. It was sounding pretty good and fuzz like so then I added a couple clipping diodes I got from I think it was allelectronics.com and really love the sound of. .I actually ended up with a really rounded and extremely heavily compressed tube sound but ultimately could not get rid of the harshness.

I have to wonder though, maybe if you cascaded enough op amps and overdrive each one the tiniest tiniest bit, you could avoid the harshness and nail the tube sound I had. It was round, glassy and compressed like a tube but far too harsh for practical use.
I'm still fascinated by the result though....

[Minion]

Your really not supposed to overdrive opamps that is why they use Clipping Diodes to simulate the Overdriven sound as opposed to just overdriveing the Opamp its" self....

If you want a Good Tubey sound without useing Tubes Try putting a Few Cascaded Fets infront of the opamp and overdrive the Fets, It should produce a more Tubey sound over useing clipping diodes......

I find a discrete design produces a much more convincing tube distortion over opamps but Transistors are much more difficult to use than our trusty opamps....

Cheers

[DrFrankenstein]

Yeah I know man, it was purely accidental but I noticed the sound was incredibly rounded and compressed. Beneath the harshness, the mass of the overdrive was in fact incredibly smooth.

This leads me to think that while it may not be possible to overdrive an op amp even if mildly overdriving numerous cascaded stages, it should be possible to design an op amp for the soul purpose of overdriving it.
I suspect the only reason one hasn't been developed is, we're not the ones behind the development.

Should be possible to lobby a company like National Semi Conductors or Texas Instruments into doing so though.

I'm also not a big believer in the tube sound, I modified my commercial chip amp out the wazoo and got a wicked sound. Sounds easily as good as any tube amp straight out of the box. Ultimately the only way I matched all these legends using tube was adding a mutl band EQ to my effects loop, the exact same thing they all do.
Oh the irony.......

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[sek]

Doctor!

Perhaps you should try different brands and types of opamps. They can have distinctively different input topologies, transistor types and protection diode schemes.

Surely, two technologically different opamps will sound different when overdriven. But all of them will have some of the harshness. This is due to their speed: semiconductors clip in a straight fashion, contributing a lot of very high frequencies to the sound. Tubes clip softly, increasing the very high frequencies last and only when driven real hard.

Cheers.

[Minion]

I also made a Guitar amp out of a Chip amp (LM3886) and it sounds increadably good for a cheap amp....

I am now looking to Build a 100w Bass amp out of Two Bridged LM3886 chips but I am looking for a Good Preamp design...

I have been trying to designg a fet Preamp but I have had a Lot of failures so far so I am getting close to decideing to Bail on the whole deiscete Idea But I really do not like the sound of Opamps for Guitar/Bass but all of the designs I have tried so far haven"t worked and all the Tube designs I have tried haven"t worked either.....I guess my Problem is the whole Biasing thing which I haven"t been able to figure out yet and that fets are so inconsistant is probably a big part of the Problem....


If you know of any Good discrete designs let me know...


Cheers

[DrFrankenstein]

sek I'm pretty sure every op amp will sound like garbage when overdriven. I just noticed that underneath the in your face harsh characteristics, there was a smooth and compressed overdrive that sounded like it had the potential to outperform tubes. As I experimented with different components and added components, the compression in some instances got just ridiculous. I cut out 90% of the treble and the THD must have been 40% though I have no way of verifying this.

You know what else, no one has developed an op amp for the soul purpose of being overdriven for use in a guitar amp. Now maybe no current op amp design can be overdriven without sounding bad but maybe the right design can or the right design coupled with the right circuit design can be.
I truly believe op amps hold the potential to yield superior results to both tubes and transistors when overdriven, no ones bothered to whole heartedly tackle the task. When it comes to fidelity, op amps are on top of the game regardless of what your ears may prefer.

I'm also a firm believer that an op amp driven distortion circuit can match tube overdrive and easily outperform it. I recently designed an op amp distortion where the clipping stage produces an asymmetrical wave form and responds to the voltage fluctuation produced by playing intensity but it has this crackle I'm having trouble getting rid of. Not sure what the culprit is which is a big chop to the teeth seeing how this circuit's sound and characteristics will be the heart of the all-chip-amp I'm designing for use with guitar.

I don't mean to get off topic here but I believe whole heartedly tube is overrated. Minion maybe this will help you, maybe it won't but where specifically are you running into short comings?
As far as overdrive/distortion goes, I say go with a simplistic op amp based distortion and use LED's rather than all the popular diodes everyone swears by. They deliver not only asymmetrical clipping but clip softly if you use the low/softer outputs, generally greens and yellows.
I suggest going dual op amp and using the second stage to drive your signal through a 3 tone stack.
As far as your amp stage goes, man all that juice is truly the holy grail!
Use some passives. There are a lot of different passives that will make incredible improvements to your overall sound that movie you into a class all your own. One that delivers the very same results of tube stage overdrive which doesn't take much effort if you're clever.
Just think, tungsten.

Sorry I can't be more specific but I often feel I give too much information away as it is. While most guys do this as a hobby and some may in fact have the same goal as myself, I plan to own my own guitar and amp company/factory some time in the not so distant future. The tips and clues I've dropped are very important elements in my designs utilizing low tech innovations resulting in high tech advancements.
Good luck utilizing them in your own designs.

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[sek]

Personally I believe in DSP programming when it comes to versatility. But if you managed to squeeze that sweet sound out of an opamp package, that would mean a lot of saved space and cost. A clear selling point.

[DrFrankenstein]

ewwww DSP

I've yet to hear a DSP, even the Vetta II Head, that can produce a distortion that sounds as good as analog. They sound good but also sound sort of plastic but think about it, the chips are silicon. Don't forget the signal loss with analog to digital conversion plus more loss once converted back to analog.
I also have a trick for running my distortion at incredibly low levels that won't work with digital distortion and maximizes performance and sound 10 fold.

On top of those personal dislikes, think about it. The Digital market is flooded with countless products and the digital amps available increase year after year. I don't think it's possible to compete in a market where no one is truly on top. Line 6 is the favored amp but processor wise, there is no top dog.

Deliver an analog amp that's affordable, loaded with features and make a name for yourself worth putting on it, that's far more marketable.

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[sek]

But your latter statement was exactly my point.

[DrFrankenstein]

I guess my real point was that I'll take analog over digital distortion or amp modeling any day, even when it sounds really good it still falls short somewhere. Any other effects though, they sound great these days, especially at 32 bit. A far better choice than a mess of stomp boxes I don't care what anyone says.

Digital will obviously one day completely take the place of chips and tubes and it's probably not far off.