4558 Op Amp

[econpatric]

Hey all,
I have a schematic for the "Tube Reamer" from runnoffgroove.com, I connected the U1a as shown, then using a different schematic as a reference I connected the second stage of the op amp as follows: pin 6 to 7 and pin 5 to ground, at this point i am getting no sound.

Will connecting the second "AMP" stage of the 4558 op amp in this way work? or does it need other components to function?

Thanks...

[StereoKills]

The Tube Reamer (http://www.runoffgroove.com/tubereamer.html) utilizes both sides of the dual opamp (4558). The only pin that should be directly connected to ground is pin 4.

Pins 6 + 7 should not directly connect, but should have the 51k resistor and 100pF cap in parallel between them.

What is this different schematic you are referencing?

[econpatric]

Ok, maybe I was a little vague. I am not trying to build the exact "tube-reamer". More directly I am trying to find out if i can utilize only one part of the op amp.

So my question is: by connecting all the necessary components (resistors, caps, etc.) to pins 2, 3 and 1, power on pin 8, and ground on pin 4, I have one part of the op amp working, can the 2nd part of the op amp be overridden by connecting pins 6&7 together and running pin 5 to ground?

[slacker]

Pin 5 would normally be connected to vref not ground, ground may work fine though.

[flintstoned]

I've been looking at madneans serendipity (Zendrive clone) the last couple days and that has pin 6 jumperrd to pin 7, check it out. My question is what's the difference between running pin 6 to 7 as opposed to just skipping the second stage, not connecting to pin 5 and running straight to the output cap?

[familyortiz]

Econ,
If I understand correctly, you are not wanting to use the 2nd opamp at all. What you describe is a way to leave an unused opamp so that it is not left unterminated, which can cause problems.
http://pdfserv.maxim-ic.com/en/an/AN1957.pdf

Are you getting a signal at the output of the first opamp?

[econpatric]

Thanks, Oritz!

That is exactly what I was trying to determine! I was working on a schematic that only used one of the amps in the 4558.

I was having some problems getting audio out of the first stage (which was caused by a wrong resistor). I had checked the entire circuit several times and was beginning to think that maybe the schematic was wrong with the way it "terminated" the second amp. After rebuilding the circuit last night I determined it was my error with the resistor. But this was still a question in my mind. Thanks!

[familyortiz]

good catch. big or small, one of the greatest satisfactions in the electronics area is fixin something!