active crossover + noise

[Calebay]

okay

I build 2 channels

12/24 dB/Octave 3-Way Linkwitz-Riley Electronic Crossover, project 9 from ESP

i made the PCB my self, both channels have own regulatet power supply, but i use the same trasformer for both channels.

there is a problem whit noise tho. when i only connect one channel ist fine. no noise. but when i then connect the the input phono plug into the other channel i get noisy. its not 50 or 100hz. alot higher. its not very loud but to much.

the same thing happens is a connect both channels in a stereo amp, if i use mono blocks there is no problem.

can anyone tell me what i have done wrong here?

Tnx, and sorry for my poor poor english hope you can read it.

here is a pic

[Jan Dupont]

It seems like you have a problem with your Gnd-connections......
You may have caused a Gnd-loop....
Remember that all Gnd connections must be wired to a common Gnd-point at you power supply.....
Have you remembered to fit the rca-plugs (phono-plugs) isolated from the cabinet, and each with its own wire to the central Gnd-point ???

[Calebay]

but why do i not get any noise the i connect only 1 channel?

the rca-plugs is soldered directly to the pcb.

can it be the groud wire to the transformer causing, this group loop. see pic

[Jan Dupont]

Hi again,
Because the second rca-plug makes the gnd-loop......
It's not easy to see the details on your picture.....
If you want to, you can contact me directly on one of my emails;
just add jd@ in front of one of my webs

[richie00boy]

Because the loop is only formed when you add the second channel.

[Calebay]

ACD you got mail