High Power Amp With TDA7250...

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#2
I have a pic with 8 tr' and TDA7250 it is near from what i want to build... the pic from the site ..

But in the pic it is hard work... i want simple with TDA7250 and 12 tr' 2SC3858-2SA1494
 

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#7
Be careful with this chip though. It seems to oscillate very easily. I have made an amplifier with this one using the TIP142/147 darlingtons as driver. They didn't seem to be too happy with clipping though, but I have a feeling that has something to do with the fact I didn't put protection diodes on the drivers...
Take a look at my schematic. I also have the pcb's for that one.
 

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#9
Haven't got a clue. I gave up working on this project because I assumed it was limited to using darlingtons. Besides I don't like the tda7250 at all. It produced quite a lot of hum with me, and with this sort of ic's.. where do you begin looking eh?
I'm going to take my chanches with the TDA7293 wich seems to be a lot easier and compact...
 
#10
That TDA7250 thing doesn't really make sense to me. With +/-45V supply rails ypu can add as much output devices as you want, the 4 ohm power won't increase.
The only chance to get reasonable more power ist to use the both amplifiers in bridge mode.
I haven't read the specs of the TDA, nor have I looked at the DPW666 solution, but I would say that a good discrete front end won't make such a big amplifier much more expensive.
So why stick to that limited driver chip?
---
Holger
 
#14
Dj BASS AMP said:
with TIP142/147 u can max get 80W x 2 in 8 ohm in
bridge u can 250W in to 8 ohm...

with MJ11015/6 u can get 400W
Click to expand...


Dj, I think you make a mistake here.
It's not because the specs of a transistor are higher that you will have more power in the same circuit.
Tip142: 100V/10A/125W
MJ11015: 120V/30A/200W
These specs only give you the maximum ratings of the transistors.
Substituting the TIP's with the MJ's will do nothing. Unless you change the whole circuit.

/Hugo
 
#15
Netlist said:



Dj, I think you make a mistake here.
It's not because the specs of a transistor are higher that you will have more power in the same circuit.
Tip142: 100V/10A/125W
MJ11015: 120V/30A/200W
These specs only give you the maximum ratings of the transistors.
Substituting the TIP's with the MJ's will do nothing. Unless you change the whole circuit.

/Hugo
Click to expand...


i dont say that he will get the power without change nothing...
he ask about the transistors... so i answer about transistors...
 
#20
With the shown schematic but TIP's instead of MJ's i have a problem.

At +/- 38 V and RL=4 ohm. when i turn on the volume over a certain point the amp shuts down and when i lower the volume the amp waits a few secs and then turns on again.

What is the problem ?

Can be that the speakers can't take the load and the amp knows that and is shutting himself off for protection ?

Thanks again for help.

P.S. Great pictures of 7250 amps.
 
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