OP275 op-amp low end issue

[PRR]

I have NO clue why "3.92K" rather than 3.9K, 5K, 10K.

Certainly the chip can't be that fussy, because 20% tolerance on absolute resistances is good for chips.

Also implied in there is +/-15V supply, and you are using less.

When the older TL072s freaked-out in hard input overdrive, it could be unsettling. I'm a bit astonished that the OP275 admits to such misdeeds.

[jojokeo]

Well the verdict is in. Drumroll............the 0.1uF cap appears to have stabilized the stringer therefore the stairs to the cellar are rigid once again making safe travels to the wine storage area now a breeze! 

Mr PRR you da man once again! It's a bit hard to believe it could be this simple and right under my nose but it is what it is. In my mind I kept thinking it seemed to be power or bias related and tried most everything that seemed reasonable. I have two more circuits built close to original form where I will try to repeat the crime so to speak, then make the correction and validate this issue. I left the 6k8 series resistor in place (trying to keep it one change at a time) so that would be way out of tolerance for the suggested 3.92k value, ha! Now I have just enough time to modify the one already in an enclosure to use for this weekend's fall festival gig and get some practice time in. SWEET!!!

Thanks to all for their time and input on this. _\m/

[jojokeo]

The things that you mention is ONLY or the OP275? Every other dual op-amp chip works fine in this circuit.

The things that TMF mentions apply to every opamp. What he says, subtly, is "read the datasheet for your opamps".

I'm very, very certain that every other dual opamp chips does not work fine in this circuit, only the ones you've tried. Every opamp is different, and has quirks of its own. Phase reversal when the opamp inputs are stressed in some way is very common. What changes is how susceptible the chip is and to what condition.

There's a common acronym for the proper response here. It's "RTFM", standing for Read The Fibbling Manual. Or datasheet in this case.

Running into the need to read the datasheets is the first step in getting out of beginner electronics.

RG - I respect your vast knowledge and you are correct about reading datasheets & manuals. I have a friend on another forum that says "Cunfuze-us say: "He who say "It can't be done" should stay out of way of him who doing it!" I am pretty much self taught since I've been building all manner of circuits, amps (tube & SS), effects, and repairing many various electronics work (also professionally working for local government) even prior to getting Craig Anderton's Electronic Effects Book back in the early 80's and when his work first began being published in the 1970's Guitar Player Magazines - respectfully, you are incorrect on several fronts here and will leave it at that. We shouldn't judge and book by it's cover (or a poster by the number of posts made).