[z2trillion]

I going to building a PPA in January (right after college apps are done), so I'm planning and buying parts right now. I have some questions, and any help with them would be greatly appreciated.

Tentative Parts List:
Hammond Case
12-17 AA rechargeable batteries
OPA637 left and right
OPA627 ground
HA3-5002 buffers ??? per channel

How will using extra buffers affect battery life? How much difference in battery life would there be if I were to use 1 buffer per channel as compared to 4?

How does biasing the PPA into class A affect battery life?

If I decide to use a pane of Plexiglas or something to make a window on one side of the case, how would this affect the shielding of the amp? Would this lead to greatly increased interference?

 

[tangent]

Quote:

How will using extra buffers affect battery life?

Each HA3-5002 chip has a quiescent current of 8.3mA. Add in the quiescent currents of your op-amps, power LED, and class A biasing, and -- to a first approximation -- you'll have your amps' total quiescent current. Divide that into the battery's mAh rating, and you'll have hours of run time. That number applies as long as you are able to run the battery pack completely down. If the amp starts clipping before the pack is depleted, you will get fewer runtime hours than predicted.

You might be wondering why I don't calculate in the current of running the headphones. It's because it's small next to the quiescent current of the amp. It's significant, but not a major factor. Also not a major factor is self-discharge of the battery pack if you're using rechargeables, as long as you don't leave the amp on a shelf for extended periods of time.

More details here: http://tangentsoft.net/audio/opamp-wv.html