Transformer Power Rating

[audioguru2]

Datasheetarchive.com found a difference: The ability to dissipate heat.

Only 3 companies make the BDW83D and BDW84D. Many companies make the C version.
A "no name brand" company makes the D with a 150W rating but ST Micro who make only the C version have a rating of only (!) 130W.

I also wouldn't build this amp that looks like it is a very old design. Check www.ampslab.com and www.sound.westhost.com/index2.html for much newer and better amp projects. 

View attachment 38390

 

[Mickey1]

I like the retros...javascript:replaceText(' ', document.postmodify.message);
Smiley I'm building this amp 'cause I want to use it in my combo guitar amp project... I don't know, I looked at the written characteristics of the amp and it looked very, very nice to me... If I'm wrong with this, I will be very, very dissapointed...javascript:replaceText(' :-\\', document.postmodify.message);
Undecided
BTW, I know that the transformer SHOULD be 2x28V/8Amps, my question was WHAT WILL HAPPEN when I put this one that I have? I think that the electrolytics will raise the voltage to about 35-38V... Will it provide less power or what?

 

[Mickey1]

Oh my God.... look at this message!!!!
HERE IT IS HOW IT SHOUD LOOK:

I like the retros... I'm building this amp 'cause I want to use it in my combo guitar amp project... I don't know, I looked at the written characteristics of the amp and it looked very, very nice to me... If I'm wrong with this, I will be very, very dissapointed

BTW, I know that the transformer SHOULD be 2x28V/8Amps, my question was WHAT WILL HAPPEN when I put this one that I have? I think that the electrolytics will raise the voltage to about 35-38V... Will it provide less power or what?

And, I do have ST Micro transistors. They'll work fine, I think...

 

[Staigen1]

Hi Mickey

It will work, but, yes, it will deliver much less power!
And the BDW83/84 C transistors will also work!

//Staigen

 

[Staigen1]

If you gonna use as for a guitar amp the put the output transistors on a real BIG cooling flange(i dont remember the right name for it now, this was in my dictionary)


//Staigen

 

[Staigen1]

Hehe, heatsink was the name for it, but it slip my mind, when i needed it! ;D ;D
I belive i'm getting old ;D ;D ???

//Staigen

 

[Mickey1]

Damn, I hope this one that I have will be big enough... I'm putting a NTC controlled cooling fan, so I think I'm doing right....

It will work, but, yes, it will deliver much less power!)


//Staigen

How much less power? Can we calculate that?

 

[Staigen1]

Hi

I'm putting a NTC controlled cooling fan

Run the fan at full speed all the time instead, i suppose it is a fan from a computer.

How much less power? Can we calculate that?

Audioguru is much better in calculating this kind of things. We can ask him.
Hey Audioguru, what do you think?

//Staigen

 

[Mickey1]

No, it's not a fan from the computer, it's actualy twice as big and it blows really good. It's PAPST cooler, you might heard of those... Hello, audioguru, we're waiting for you... Will I get an answer to my question?

 

[audioguru2]

Since 100W into 8 ohms has a p-p voltage of 80V, then this project can't produce anywhere near its rated 100W with only a positive and negative 40V supply from a dual 30VAC transformer.
It has a voltage loss of about 7V so the dual 30.5VDC from a dual 23VAC transformer is reduced to 54VDC, which is 45.5W into 8 ohms at clipping.

 

[ante1]

Hi Guys,

The newer package (SOT-93) has a better ability to dispose heat than the older (TO-218). At least that’s how it seems! These two packages are very similar to look at but internally the “chip” has probably a better thermal contact to the metal tab.

 

[faizanbrohi]

I have got 2NU41 Rectifier Diodes , will it work on 6A or not , i am talking about the power supply. I have seen the graph in the datasheet and it has high current ratings

 

[faizanbrohi]

Well i have all the transistors , diode and i felt lucky in getting the exact Darlington pair both are from texas instruments and are BDW84D and BDW83D respectively
so now how will it behave , how much watt  ???

 

[audioguru2]

As I said at the beginning of this thread, a 28VAC transformer won't make 40VDC at its full loading, but if this circuit has positive and negative 40V then the amp will probably provide 85W into 8 ohms or 140W into 4 ohms.

 

[faizanbrohi]

Good I have a 4 ohms speaker , so it will deliver 140W RMS??

 

[audioguru2]

Good I have a 4 ohms speaker , so it will deliver 140W RMS??

Yes I think it will, if your power supply is strong enough.

 

[faizanbrohi]

I have a Transformer capable of delevering 8A @  2 x 28V . and one more thing , i could not found P600B , can i use a simple 1000V @ 6A diodes that i can find , i don't have the exact number , but i will if i buy it

 

[audioguru2]

I have a Transformer capable of delevering 8A @

 

[faizanbrohi]

ok then i am preparing to add something else , temprature meter , fan , and a Power meter that shows the actual wattage, for power measurment i will be using  a ADC to measure voltage and current and then when it is binary form , digitaly multiply them using logic gates , and then convert the binary power output to 7 segment using a BCD to 7 segment decoder . how is the idea ..

 

[audioguru2]

Why make a complicated power meter? The power changes in less than a milli-second so a 7-segment display will be a blur.
You hear loudness, not power. Just make an LM3915 LED bar-graph sound level meter or voltmeter. Have a peak-detect circuit to hold readings for about 50milli-seconds so they are visible.