Power Supply -50V gnd +50V


I'm a newbie in DIY Audio but I have a little experience in electronics :D I want to build a first cheap system just for fun & tests. I have seen this article which look good ! :) I want to order some different parts but I have a problem with the power supply !

The amp is very cheap, but PSU is expensive :eek: And I have some questions !

On the datasheet there is a 2*35V transformer but the output voltage is 50V : is-it normally ? :eek:
I want to order a 2*35V transformer (what is the VA stock ? I have seen 5A, so 350/400 VA is good or not ?) but is VERY expensive ...

Can you help me please ? Thanks :rolleyes:

PS : I'am french, sorry for my amazing bad english :D
Thanks ! I want the cheaper ;)

And, in the post, I have new questions !

"And When connected to the bridge adapter with output altitude of about 400 watts is incredible." What is this ? The output power is 2*100W or not ?

"This our circuit use dual voltage positive – negative 50 volt and current is 5 Amp, we so use power supply as this figure which." Can you explain to me the details of the calculation of the capacity of the transformer VA ? I think I have not totaly understand ...

Please help me :)
100w out put=v²/r; r=8 ohm; v=28.28 vrms
100w=i²*r; i=3.53 amp rms;
in order to convert these numbers to vdc of one rail of the power supply have to add the loss of the output stage and bridge rectifiers, efficiency of the power transformer and multiply by √2.
((28.28+5+1.4)/0.96)* √2=51.86 vdc
This will a sure you the voltage swing for 100w output.
The current will be: 3.53* √2=5 amp dc.
I hope I did a little for your calculus.
Best regards,
1) As a very loose calculation, you need *at least* 50% more VA than the RMS power and preferably 100% more so for 2x100W amplifier you'll need at least a 300VA transformer (and that would be for home use) to 400VA.
If you go higher, it does not hurt :)
Load each channel with a normal 8 ohms speaker (or cabinet) and you'll be fine.
Don't bridge it, or load with 4 ohms, etc., just work well within its specs, not worth getting close to the limits.
Anyway you already have a very powerful amplifier.

2) the heatsink shown in the project page is *very* small, guaranteed to burn your amplidier.
At most it's suitable for a single 50/60W chipamp or less.
You'll need something like:

from around 20 cm wide, at least 10 cm high.
Or better.
Bien sûr !! :)

Back to electronics: this is not a transformer but a 36V DC regulated switching power supply.
*Maybe* two of these can supply a power amp which needs those rails , but it's useless for you.
*Plus* it's in China, you have to pay extra for shipment but even worse, any Tax or Customs Duty is extra.
Try to get a transformer locally or at least within the E.U., transformers are heavy and pay a lot.