I constructed this circuit as shown for use as a simple headphone amplifier. I was so happy with myself that I made a second one for stereo, as well as using a 3915 to make a very simple volume visualizer.
The circuit uses a uA/LM741 as a "preamp" for the 386 audio amplifier. Through my reading, I learned there are much better op-amps to use for audio applications than a 741, such as the TL071. So, imagine my gaiety when I discovered a set of TL071s in my parts box. Well, I'll just plug them in (swapping the TL071 in where the 741 is without changing the circuit otherwise) and...
No dice. I have to change the bias on pin 3 (the noninverting input) so that it's biased at Vcc/2, which ends up limiting the amount of "volume" I can get out as well.
My question is, why can the 741 have its NI input hooked to ground and still function fine, but the TL071 needs a "typical" mid-supply bias?
I know that the 741 is a BJT-based design and the TL071 is a JFET op-amp, and you'll have to excuse me but I'm still just learning about FETs at the moment. Is this because of the larger offset voltage in the TL071 because it's harder to match device parameters in a FET?