2. amps-preamps
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Same power supply from piano and amplifier

I have a digital piano with LINE OUT. I also have a mini amplifier named "pam8610" (cheap and very common) which has LINE IN. I have 2 power supplies, each one with 12V and 5A. When I connect each power supply to each device (one power supply to the piano and the other power supply to the mini amplifier) everything works just fine: when I play the piano the sound goes to the mini amplifier and then goes to the speaker.

HOWEVER, when I connect both devices (piano and mini amplifier) to the same power supply while keeping the LINE connected, my piano turns off immediatly, something is really wrong. If I disconnect the LINE and use the same power supply, no problem happens (but of course no sound is produced because the LINE is not connected).

Using a multimeter, I discovered that the GND of the LINE OUT is the same GND of the power supply (continuity test in the multimeter). I dont know if this is common practice, but for some reason my piano provides the LINE OUT with the same GND of the power supply. So, when I use the same power supply to power the mini amplifier and when I connect the LINE, some kind of short is happening. Using 2 separated power supplies, everything works fine.

Do you guys have any idea how can I fix this or what is going on?
 

batata004
erik_squires
16,007 posts
 

Have you considered that you need more current??

Current draw per device adds.  So if you have 2 x 4A devices you need a total of 8A..

jasonbourne52's avatar
jasonbourne52
2,863 posts
 

Stick with using a separate power supply to each device.

imhififan's avatar
imhififan
2,174 posts
 

I think the problem is the power supply ground of the "pam8610" should not connect to its INPUT "ground". You can use continuity test in a multimeter to confirm that.

If you using 2 separated power supplies and connect both power supply negative together, I think the piano will shout down as well.

 

 

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