Psu Lm3886

[Mayday]

Yes it is. I've gone for higher VA, but that's more or less overkill.

[ppcblaster]

Thank you.

The datasheet states 35V at about max.

Is 35V rail the safe max or can I go higher?

First time build for me....

[AndrewT]

Originally posted by ppcblaster
Is the AVEL Y236652 250VA 25V+25V TOROIDAL a good choice?

yes, that will support three channels @ 60W into 8ohms.
You might just be able to stretch to 4channels out of it. But hum reduction on multi channel from one trafo seems to be a problem with the PCBs as supplied.

Do not go any higher with 8ohm speakers.
If you allow for max mains voltage and max transformer regulation and minimum quiescent current in the chipamp you will have a lot more than +-35Vdc in the worst case (fortunately not too often).
If you have 4 to 8 ohm speakers then 25Vac is already too high.

[ppcblaster]

Originally posted by AndrewT
yes, that will support three channels @ 60W into 8ohms.
You might just be able to stretch to 4channels out of it. But hum reduction on multi channel from one trafo seems to be a problem with the PCBs as supplied.

AndrewT,

Please explain,

[Mayday]

I missed something...are you going for more than two channels?

[ppcblaster]

Originally posted by Mayday
I missed something...are you going for more than two channels?

No, just two channels at this time.

[Mayday]

I'm rather sure that I read that if you use only one psu board, then there'll be no problem with humming when using only one transformer, there's not even enough ac inputs in a stereo kit to use dual transformers.

[AndrewT]

Hi Ppc,
how far do you want me to go back?

25Vac gives about 34 to 37Vdc.
This results in about 60W into 8ohms.
2 channels is 60+60=120W and a 120 to 180VA transformer can meet this demand.
Your selection has a capacity of about 50% to 100% more than that, indicating that 3 or 4 channels could be powered from this transformer (if you had that need).

If one were building a 5.1 system, the simultaneous demand from all the channels rarely matches the sum of the channels and if the sub were run from a separate transformer (or separate windings off the same transformer) then the 5channels may/will run successfully from a smaller transformer than normally recommended.

hum.

mayday and a few others are finding a problem silencing stereo and multi-channel chipamps. There are solutions, but they seem to vary from build to build. Be prepared for experimentation - bolted ground connections are a lot easier than soldered!

[Mayday]

Don't forget proper fusing, lot less expensive to have a fuse blow than say a 10000uF cap.

[ppcblaster]

Thank You