Electronics 2000

Hello guys. Thanks for reading, I've been wracking my brains about this and could really use some help.
I have a MOOER Lofi Machine. It's a bitcrushing pedal for guitar/synth what have you. I am trying to convert it to run from a 9v battery instead of having to plug it into the mains, making it portable.
I assumed that it would be as simple as connecting a 9v battery but it appears that does not power the pedal. I have tried 6 AA batteries (@1.5V each) as well and still nothing.
I am fairly certain that I need more power but I'm not sure what manifestation that should come in. I would like to keep the power supply as small as possible.
The adapter output is 9v 200mA.
Here are the pedal specs:
Input: 1/4” monaural jack (impedance: 470k Ohms)
Output: 1/4” monaural jack (impedance: 100 Ohms)
Power Requirements: AC adapter 9V DC (center minus plug)
Current Draw: 128mA

Any help would be much appreciated!

What is the spec of the adaptor?
You say -9v in the title so it is making me think you may have your polarity incorrect. To get -9v with centre pin 0v you need to connect the positive of the 9v battery to the centre pin and negative to the outer barrel.

Got it. It was centre negative! Also had a lot of feedback with 9v battery but switched to 6xAA and works like a dream. Thanks very much

Feedback is where you have a complete loop and it feeds back into itself i.e. a microphone near a speaker which causes a squeal.
I don't see any reason why a 9v pp3 will cause this, nor why 6xAA doesn't. Both will provide DC as smooth as a baby's bum (the voltage is from a chemical source, not derived from a sin wave as you get from a mains adaptor).

Just on feedback-> (im going to get punched for this hehe)

its amazing that is.
Feedback is an amazingly useful thing, where one can use his output in the next input. (VERY! important to be able to do it.)

In the case of speaker mic feedback, u can see you have now created the phenomenon, doing it in a circuit tho, I was battling for a long time, because it needs to be between 2 op amps, or some kind of segregation or it doesnt work so well. I dont know at this stage. but getting that wicked squeal out of the speaker is a damn useful thing, if it were a computation happening.