tda2030/40 power supply doubts and guidance

[jogina111]

Hi, I'm planning on
making another
practice amp and
this time, using a
TDA2030/40/50. So I
checked what components I'm missing.
The only problem I
saw is these amp
chips USES SPLIT POWER
SUPPLIES YET WHAT I
have left is a 21v laptop power supply..
I'm also planning on
powering the preamp
from the same power
supply since it got a
lot of power. Any tips on how I can get this
to work?
Also, i have some
lm317 I think I'm gonna
use to limit the
voltage to the preamp..

 

[JonSnell Electronic]

Google Image Result for http://www.electronica.ro/audio/images/TDA2030A.gif

Single ended amplifier diagrammes are shown on this page.
All you require is a centre point for reference. The Chips have excellent signal to noise properties and do not require a stabilized power supply. Nice and simple!

 

[gootee]

Starting with 21V, your maximum/peak signal output voltage would end up as 21V - ripple voltage - 2 x clipping/dropout voltage of chip. The clipping/dropout voltage might be 3 to 4 Volts for each power input and the p-p ripple voltage will depend on the power supply and any reservoir and decoupling capacitance that you might add. But if we say the best case would be a total of 8 volts, your maximum peak to peak output is then at 13V, equivalent to +/- 6.5V.

That would make the maximum RMS output power = ( 6.5 / sqrt(2) )² / 8 = 2.6 Watts into 8 Ohms, or 5.3 Watts into 4 Ohms. And that's with it turned ALL the way up to where it starts to clip.

You will probably want a higher power supply voltage.

By the way, here is the official datasheet, which includes recommended schematics as well as specs:

http://www.st.com/st-web-ui/static/...ding_block/site_media/icon/pdf_icon_large.jpg

 

[gootee]

Sorry. Here is the actual PDF datasheet link:

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00000129.pdf


Maybe you could actually get 4 Watts/8 or 7 Watts/4 instead of 2.6W/8 or 5.3W/4, starting with 21V.

Or, you could build Fig 15 instead of Fig 4. That should give you a solid 8 Watts into 4 Ohms.