suggestion needed for transformer

[Hosam]

I tried 1.5 ampere transformer 24v for power supply for preamp almost finish,and it works great when only use it for each parts as supply, but when I change it to 24v 15 ampere transformer it give me high hum but that necessary for all together.
well the needed to high ampere transformer is to get suitable power supply that handle these:
- LM3886 single chip
- TDA7294 single chip
- EQ 10 band
- X- cross filter.
- TDA7294 dual bridge mode.
what could you suggest me to use single power supply for each of them or the 15 ampere transformer I have and then get power supply for all of them?
I just want to make sure the hum is gone, my grounding is surely working I check everything, what could else be the problem that reduce the hum all the way?

[mastodon]

Sounds like it's not the transformer that's the problem, but inadequate power supply filtering or stabilization. Can you post a schematic of the power supply and the calculated power requirements (i.e. how much current will be drawn from which voltages)?

[Ellenic]

Sometimes if you cut the earth wire the hum sound dissapears...You will have to experiment a little...
Are you in Syria or Canada?
Also as mastodon posted it would be better to post scematic to make sure everything
is ok from the power supply

[Ellenic]

Also , do you have hum sound with the input plugged in?or without?

[Hosam]

I use this for power supply in general for all

more explanation:
TDA single use single power supply 24v 1.5A transformer+10A bridge+4700uf/50v x4+220nf ceramic capacitor as filtering part.
TDA dual use single power supply 24v 3A transformer+10A bridge+4700uf/50v x4+220nf ceramic capacitor as filtering part.
LM single use single power supply 24v 3A transformer+10A bridge+2200uf/50v x4+100nf ceramic capacitor as filtering part.
EQ use single power supply 15v 1.5A transformer+10A bridge+2200uf/50v x2+100nf ceramic capacitor as filtering part.
X-Cross filter using the same power supply for LM.
all working great alone if they each have one power supply, combination making the problem.
I wish to make this work, but I don't know where is the problem come from the power supply part or the transformer itself.
it both hum sound with input or without it, for the input I use the same ground point with power supply.

[Hosam]

Originally Posted by mastodon

Sounds like it's not the transformer that's the problem, but inadequate power supply filtering or stabilization. Can you post a schematic of the power supply and the calculated power requirements (i.e. how much current will be drawn from which voltages)?

for the schematic its in the picture I could help with more if you need but its temp power I used in temp fiber not 100% finish.
for calculated its in previous post.

Originally Posted by Ellenic

Sometimes if you cut the earth wire the hum sound dissapears...You will have to experiment a little...
Are you in Syria or Canada?
Also as mastodon posted it would be better to post scematic to make sure everything
is ok from the power supply

now I"m in Syria and I did experiments on the power with multi meter and it give right voltage for output power requirement.

Originally Posted by Ellenic

Also , do you have hum sound with the input plugged in?or without?

both I have hum but its disappear when load come I mean full load you then could not know if there is still hum or not but when music stop even for 0.5s then it come back.
for input I test 4 types: PC sound card - Laptop headphone output - Cell phone headphone output - Ipod.
I still facing this problem now I think I'll try to use regulator for more filtering hope this help.

[AndrewT]

Hosam,
you cannot use a centre tapped transformer with dual bridge rectifiers to create a dual polarity power supply.
Either use a dual secondary or use a single bridge rectifier.

Assemble a mains light bulb tester.
Plug in every new or modified mains powered project to the tester to prove you have not made a mistake.

You will find that the bulb lights up when you plug in your transformer with that rectifier arrangement.

BTW,
the hum from the transformer is the wires vibrating when passing hundreds of amperes.
You will very quickly burn out your transformer playing with it like this !!!!!!

You are the most dangerous of all DIYers. You don't realise enough to know when there is a danger to your life or limb !

[Hosam]

Originally Posted by AndrewT

Hosam,
you cannot use a centre tapped transformer with dual bridge rectifiers to create a dual polarity power supply.
Either use a dual secondary or use a single bridge rectifier.

Assemble a mains light bulb tester.
Plug in every new or modified mains powered project to the tester to prove you have not made a mistake.

You will find that the bulb lights up when you plug in your transformer with that rectifier arrangement.

BTW,
the hum from the transformer is the wires vibrating when passing hundreds of amperes.
You will very quickly burn out your transformer playing with it like this !!!!!!

You are the most dangerous of all DIYers. You don't realise enough to know when there is a danger to your life or limb !

you're correct in one way and wrong in the other. for center tap I'm sure it has problem that's why I ask in the main topic header for help with transformer itself. but I don't have toroidal to use instead of center tap type.
Note: I'm not suggest this build for anyone doesn't have experience at all if I take your words about dangerous part of this one.
so the hum here come from wire vibrating so how can I solve this part?
do you think vibrating could solve if I use two diodes and 680ohm resistor with 100nf to the ground?
and for safety consider I use 5A fuses one both channels before the bridges they didn't blow up at all is it still danger to use in such a way?
for the equipments I use separated power for each one I mention that before and I repeat it again, but problem comes with combination part and I want to make that because my amp case is small and can't handle all of them together can you suggest me best way to make power supply that handle all mention above with safety consideration?

[AndrewT]

Hi,
it does not matter one iota that it is an EI, or a toroid, or an Rcore, or a Ccore.
What matters is that you have used a dual bridge on a centre tapped secondary to create a dual polarity PSU. That does not work.
It will overheat your transformer and given long enough will burn it out. If the overheated primary starts to short out, there is potential for an explosion. The "energy" available from the mains before the fuse or MCB opens is enormous !!!!!


Assemble that bulb tester and stop arguing.

[Hosam]

ok I'll post it when finish with bulb test to make sure everything is safe enough, but again I need the solution for the major problem one power instead of multi power...