No idea what a "push-pull pot" is. Are you talking about a decoupling circuit/high pass filter?
If so then no, you don't need that for what you're trying to do. All you need is a dual potentiometer.
A good number to aim for is around 200 Ohms, since normal headphones are around 60-600 Ohms. You'll want the parallel resistance of the potentiometer and the audio input resistance to be equal to your ipod's output impedance.
Here's how you wire it:
Ipod Left Channel O-------------
|
---
| |R1 (200E)
| |<------------------O Amp Left Channel
| |
---
|
---
GND
Ipod Right Channel O-------------
|
---
| |R1 (200E)
| |<------------------O Amp Right Channel
| |
---
|
---
GND
Ipod GND O---- ---------------O Amp GND
| |
--- ---
GND GND
Again, get a dual potentiometer so you can set the left and right channels using the same knob.
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