Bipolar Supply:
+V
GND (0V) <---connect unused inputs and outputs to here
-V
Single Supply:
+V
GND (0V) <---connect unused inputs and outputs to here
It doesn't matter if you don't use bipolar supply- You still have a GND at 0V in both cases. Short the + input, -input AND the op-amp output and connect all of them to ground. You also ground the output so it does not stay floating voltage and act like an antennae and pick up noise (that is the reason you ground the unused inputs. Unused outputs can do the same thing so you must also ground them.)
*CORRECTION* grounding outputs is a very bad idea as pointed out in following posts.
Oh yeah, my bad about the output. Sorry. Forgot that it would cause some kind of short. I was assuming that you couldn't disable individual op-amps since its a quad-op-amp, but powering it down is best if possible (ground +V like styx said) And then wiring the inputs and outputs to be a buffer to deal with the floating output.
NEVER connect the output of an opamp to ground! It will get very hot.
Connect the non-inverting input (+) to ground, then connect the inverting input (-) to the output so the opamp is a follower with ground as its input.
Thank you , guys for your help!
I almost put all staf together and now thinking if I can put 600 -600 trans as a load for the buffers (TL084) just for the line level .
Why use an output transformer? It reduces frequency response and adds distortion.
A TL084 and most other opamps can't drive a load as low as 600 ohms. The minimum load on the datasheet is 2k ohms.
Dual NE5532 opamps can drive a 600 ohm load.
I need balanced output , and I dont need a wide frequency response, its just for voice system .
The signal for the buffer only -20 db , I think its Ok , what you think? ( I mean
600 -600 trans as a load before power amp)