# Change battery input with a power adaptor

1. Apr 16, 2009

### nitronics

hi I have a guitar hero world tour drum and it is only powered by 2 AAA batteries.

Basically, I want to connect it to the wall by connecting a AC to DC adapter (110 to 3V) and connect a DC input to the red/black wire that was on the battery compartment.

Is it possible to do that ?

I will provide you a picture of the thing.

thanks for all

2. Apr 16, 2009

### vk6kro

Yes, you can do that.
You would need a bit of extra information, though.

If you put the batteries back in it, try to get an ammeter in series with them to get an idea of the current being taken from the batteries.
See if it varies much when you operate the equipment. If it does, you will need a regulated power source. The voltage has to stay fairly constant under varying load current.

In any case, you will need a filtered supply. Crude supplies only rectify the output and do not filter it. This is OK for battery charging but not suitable for your application, where the supply has to be hum free.

Take the current figures and the need for a filtered power source to a good electronics store and they should be able to help you.

Be very careful about polarity when you connect it.

3. Apr 17, 2009

### nitronics

what do you mean by filtered power ?

I got it working by soldering a dc input. There was a red and black wires going to the battery compartment. I cut them and soldered the red one in the center and the black one to the edge of the input.

The dc input is connected to a power adapter 110v to 3v. According to you, I can have
surcharge with this configuration ?

thanks

4. Apr 17, 2009

### mgb_phys

A perfect DC supply is a constant voltage.
A cheap one will have variations at the mains frequency (50/60Hz) and probably at 2x and 4x this frequency. If you are using it for a guitar amp you will probably hear this as a hum.

Cheap unstabilized supplies also have a voltage that can depend on the load. So when you first plug it into the guitar it might deliver more than 3V which might damage the amp.

It's probably worth spending $20 on a stabilized supply (look for 'stabilized' written on it) than a$5-10 cheap unit.

5. Apr 17, 2009

### nitronics

and how do I verify if my power adapter is good or not ? using a multimeter ?

thanks

6. Apr 17, 2009

### mgb_phys

A multimeter will tell you if it is giving 3V when not connected to anything (check with the multimeter before connecting it to the guitar)
TO see the noise wou would need a scope - or if it is safely 3V just connect to the guitar and see if you can hear any noise

7. Apr 17, 2009

### nitronics

hear any noise ?

I use it to give current to my electronic wireless drum to getting rid of the batteries. I don't really know how to hear any noise from this.

I did a test with my multi and it gives me a constant voltage of 3.25.

thanks

8. Apr 17, 2009

### mgb_phys

Yes it will be fine for a computer game drum kit.
I read the reply and assumed this was guitar amp which will be very sensitive to any electrical noise so you would hear a hum from the speakers when you were playing the 'real' guitar

9. Apr 17, 2009

### nitronics

ok good thank you all for your help

really appreciated :-)

great forum

bye