Redundant questions about Op-Amps...

[phaeton]

If there is any sort of documentation i've missed that spells all this out please direct me!

I'm trying to build just a simple single-stage opamp boost for experimentation purposes with minimal luck. I've been googling and studying opamps for what feels like ages now.  I'm starting to doubt whether I have any business messing with DIY electronics at all because i keep mostly hitting on nothing when I go to the breadboard.  I have a few questions about things that I think are tripping me up:

1) Inverted vs. non-inverted.  For our purposes here (boosting a weak guitar signal up to a level where we can do things to it) are there any advantages/disadvantages to building an inverting or non-inverting stage?  I understand that the non-inverting cannot attenuate, but that doesn't concern me.  I notice that most pedals are built upon non-inverting stages.  Is this one of those things where "they both work, they're both just as good, and they're just different 'flavors'".... sort of like switching out transistor types?

2) Vref or grounded + input when using inverting stage.  You guys might remember this topic I posted sometime back.  My schematic was only critically flawed in that i put the non-inverting input straight to ground.  It was explained that doing so biased the opamp "off" and the fix would be to connect it to a V/2.  Makes sense, however, most every other implementation I see of an inverting stage such as Richardo's tutorial, the TL072 datasheet (pdf file, page 8 of 18), or other misc. sources put the non-inverting input to ground.  Sometimes through a resistor, other times directly wired.  I must be missing something?

3) Jfet vs. Bipolar opamps I assume that (for the most part) all the common generic opamps we use in here (JRC4558, TL0x2, 741, NE5532 et al) are all interchangeable so long as you look at the pinouts on the data sheet and put all the connections in the right places.  In other words, if I were to see some lm741 based amplifier circuit schematic, i could substitute a TL082 without any showstopping biasing/impedance/oscillation/ issues.  Drop it in and it'll work as an amplifier- good bad or ugly is beside the point.  There is no special biasing stuff like you do when trading bipolar transistors for jfets, right?

4)Troubleshooting with ICs  The only thing I've gotten to make any kind of noise at all is Jack Orman's buffer (yes, i note the Vref connection on the + input).  I can get sound to come through it as-is.  If i apply my basic gain calculation rules and change the resistors around (R1==10K, R2=1M for a gain of 100 or R1=100K, R2=10M for gain of 100) it doesn't seem to get any louder, but it does distort in a crumbly, almost mis-biased sort of way.  No matter if i include or disclude the 5pf circuit.  I'm actually using a TL082 instead of TL072 (and fwiw, my datasheet claims that pin 8 is V+ instead of pin 7) but I assume either chip would be nearly identical in operation.  Is there a methodical troubleshooting routine for opamp chips like the effects debug over at Geofex?  (I see that R.G. always intended on including this, but hasn't ever the time... )

5) Calculating a Tee-network for gain  I realize i must learn to walk before I can crawl, but does anyone happen to have the equation handy to calculate gain for a tee network?  Someday I'd like to have a lot of fun punishing some chips  , but i haven't been able to dig up the math part.

I have plenty more questions, but I think I'll stop with these here for now, as some responses may inadvertently answer some of the others....


Thanks for any and all....

[Mark Hammer]

A lot of this is nicely addressed in a series of articles in the old DEVICE newsletters (hammer.ampage.org see pages 10-11).

[phaeton]

Thanks Mark.  I had completely missed those articles (unsurprisingly).  I'll read through them and post back with any remaining questions.

In the meantime, I am happy to note that I had some success playing around with a 741 last night.  I would have hoped for some more clean headroom before distortion from an opamp, but iirc the 741 is way over on the 'crap' end of the hifi scale (by modern standards).  The distortion it made was useable though, if not a little muddy.

I had lots o' fun!

And then I tried messing 'round with the TL082 again and continued to strike out.  Oh well.

[jxoco]

I don't know anything, but....

Here is a OP amp tutorial you should read.

best of luck

[phaeton]

I don't know anything, but....

Here is a OP amp tutorial you should read.

best of luck

Thanks! 

But where?

[twabelljr]

     Could this be it?

                   http://www.uoguelph.ca/~antoon/gadgets/741/741.html