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 😀
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 😀
35Vac makes to almost 50Vcc so yes that is ok. ( well it actually makes about 47-47,5Vcc cus of the voltage drop on the bridge rectifyer ). So make the power transformer 2X35Vac @5 or 6A depending on what you are able to find, the latter ofcourse would be better.
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 😉
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 😉
Well as u can see we are from different countryes, so no, i have no ideea about the shops from your country 😉
Anyway, i doubt u will find a cheap and new of the shelf power transformer, maybe used ones...
Anyway, i doubt u will find a cheap and new of the shelf power transformer, maybe used ones...
Ok thanks for the advise ! I can order in some different contry, if shipping costs are not expensive and if paypal is available 🙂
35V * srqrt(2) - 2x0,6 = 48,3V, perfectly normal.
I'm in Belgium and will check if I have a suitable transformer for you. I suppose you want a toroidal?
I'm in Belgium and will check if I have a suitable transformer for you. I suppose you want a toroidal?
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 🙂
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
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, thanks for your advise !
I search the VA capacity of my transformer, so 5A = x VA, x = ?
On internet I have seen 2*35V 100VA to 500VA transformer, for price 30 to 150 € ... 😉
Best regards
I search the VA capacity of my transformer, so 5A = x VA, x = ?
On internet I have seen 2*35V 100VA to 500VA transformer, for price 30 to 150 € ... 😉
Best regards
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
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
So, if my calculs are goods 🙂
8 ohms = 100W = 5A = 360VA
4 ohms = 200W = 10A = 720 VA
2 ohms = 400W = 20A = 1440 VA
1 ohms = 800W = 40A = 2880 VA
...
It's ok ? 🙂
Thanks
8 ohms = 100W = 5A = 360VA
4 ohms = 200W = 10A = 720 VA
2 ohms = 400W = 20A = 1440 VA
1 ohms = 800W = 40A = 2880 VA
...
It's ok ? 🙂
Thanks
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.
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.
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$, 36V with several output (3*"36V+", 3*"Gnd" and 3*"36V-") for 9.7A 🙂
2) thanks for this advise
And, the transformer is it necessarily a torroidal ? I have find on ebay a led transformer : 30$, 36V with several output (3*"36V+", 3*"Gnd" and 3*"36V-") for 9.7A 🙂
2) thanks for this advise
1) Yes. You will burn it.
1.5) post the EBay link.
As you write it, it's wrong.
Plus I don't believe you can buy a 72Vx9.7A=700VA transformer for $30.
So you must have read something wrong.
2) Il n'ya pas de quoi.
1.5) post the EBay link.
As you write it, it's wrong.
Plus I don't believe you can buy a 72Vx9.7A=700VA transformer for $30.
So you must have read something wrong.
2) Il n'ya pas de quoi.
Tu parles français ? 🙂
Here is the "transformer"
36V DC 9 7A 350W Regulated Switching Power Supply | eBay
So ... I don't know if is good or not !
Best regards,
Here is the "transformer"
36V DC 9 7A 350W Regulated Switching Power Supply | eBay
So ... I don't know if is good or not !
Best regards,
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.
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.
Probably, but check Italy .
Or Eastern Europe such as Poland/Czechoslovakia/Yugoslavia .
I use the old names to avoid long lists 😉
Or Eastern Europe such as Poland/Czechoslovakia/Yugoslavia .
I use the old names to avoid long lists 😉
Finnaly I have find (within 15km from my home) a used toroidal transformer 2*35V 300VA with invoice and warranty for 30€ ...
I think is it the best price, no ?
Thanks
I think is it the best price, no ?
Thanks
- Status
- Not open for further replies.