I'm looking at CONN4, which provides the input for the 9V DC power supply, and I'm not seeing any way that it is isolating the 9V battery from the 9V DC power. From looking at the KLDX_0202 Datasheet, pins 2 and 3 will always be connected. That means that if there is a battery attached, and the 9V DC power supply is plugged it, 9V will be placed across the battery. The battery is likely providing less than 9V, and the power supply will therefore push current into the battery. If the battery is a primary cell, this is a Bad Thing.

Is there something I'm missing?

Hi, the DC power jack connector datasheet could be a bit tricky to understand. In fact pins 2 and 3 are shorted normally BUT when an external adapter is inserted, this pin2-pin3 link is broken, so the 9V battery (pin 3) gets diaconnected.

There is a great article explaining how to wire this parts in guitar pedals here:

diystrat.blogspot.co.uk/2009/06/how-to-w...fects-pedal.html?m=1

Awesome! I figured there was probably something like that, but it is definitely NOT apparent on the datasheet.

Nice work on this amp, BTW. I loved the explanation going through the different stages. Cheers!

The board has top TABs on the top and bottom of the 9v battery area.
They are not connected to any of the PCB traces.
So... what are they for?
My guess is they are some sort of anchor points to hold the battery in place.

Hi,
You got it!
The TABs that you mentioned are just to keep the 9V battery in place. They are not attached to any trace and they are not mandatory for the design.