Power Supply -50V gnd +50V

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Hi,

I'm a newbie in DIY Audio but I have a little experience in electronics 😀 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 😱 And I have some questions !

On the datasheet there is a 2*35V transformer but the output voltage is 50V : is-it normally ? 😱
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 🙄

PS : I'am french, sorry for my amazing bad english 😀
 
Thanks for your attention 🙂

I have read an article for the output voltage and I have understand 😀
Do you know a shop for the cheaper 2*35V transformer please ? I want not the best quality, just a little first device 😉
 
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 🙂
 
hi,
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,
Williams
 
hi,
now do it so:
51 vdc/√2=36 v ac, taken in this case the max loss and full load for a 8 ohm
36*2*5=360 va
If you want ability of driving higher loads like 4 or 2 ohms, you will increase the current and the power va, that will increase linear.
Best regards,
Williams
 
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:
black_heatsink.jpg

from around 20 cm wide, at least 10 cm high.
Or better.
 
1) Ok, why I can't load into 4 or 2 ohms ? The amplifier going to be dead ?
And, the transformer is it necessarily a torroidal ? I have find on ebay a led transformer : 30$, 36V with several output (3*"36V+", 3*"Gnd" and 3*"36V-") for 9.7A 🙂

2) thanks for this advise
 
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.
 
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