40Watt amp transistor substitute

[ali_moinuddin]

HI friends

I found this schematic of 40watt amp using TDA2030A and two transistors BD711 and BD712


is it possible that i can replace BD711 with 2N3055 and BD712 with 2N2955

coz i dont have BD711 and BD712 i have instead 2n3055 and 2N2955

please advice

thanks

[djk]

3055/2955 should be OK.

[destroyer X]

Modern ones can hold that voltage and current...just catch a modern one and you gonna be ready to go.

Will be really hard to find an unit that will not work..... the output ones must the big ones..avoiding TO220, not using those mid power units you will be happy..and even some TO220 will fit too.

Into 8 ohms all them will be safe..... using 4 ohms you will need to made a more carefull selection.

regards,

Carlos

[djk]

"Modern ones can hold that voltage and current..."

It's single-ended 44V, cap coupled output.

[ali_moinuddin]

thanks guys ,
i tried 2955 and 3055 but the Amp power remains the same .
If i remove the output transistors and use only tda2030A and connect the speaker to the pin 4 " of tda2030a" the power out put is the same .

[AndrewT]

Originally posted by ali_moinuddin
i tried 2955 and 3055 but the Amp power remains the same .

Hi,
why should the power output change?

The maximum output voltage is approximately Vcc/2 - 4volts, i.e. ~18Vpk.
The maximum power into an 8r0 load will be ~ 20W

To be able to deliver this maximum power into an 8r0 resistive load the amplifier must be able to pass 2.5Apk from the PSU to the load.
To produce decent sound quality, the amplifier should be able to pass ~7Apk to the 8ohm reactive speaker load to achieve that 20W maximum.

[jaycee]

Correct, you are not going to get more watts just by adding output transistors. You need to increase voltage swing, and you can't do that with this circuit.

[djk]

The 'boosted' configuration is to drive 40W into a 4R load.

http://www.st.com/stonline/products/...re/ds/1459.pdf

If you bridge two of the 'boosted' units with an adequate supply you can get 80W/8R and 150W/4R.

[sakis]

if it was in my hand i would destroy the chip forum totaly ha ha ha ha

the particular circuit though has excelent dynamics and given the simplicity is made and the cost is a very fine amplifier . a better capacitor in the outpout . a better bypass . a ruged power supply and no mater if the quality is fairly low it actually has very nice "drive " ability

it can drive strange loads long cables and eventhough the power and the quality is low ..... dynamics are very good and the amp sounds more that it realy is

i would go for bd249-250 or tip 3055 and 2955 that are more available

of course modern devices like 1943 5200 will also work

regards sakis