Simple 200W Amp

[NinjaKitten]

I found a very simple 200W audio amplifier schematic:

http://www.mif.pg.gda.pl/homepages/t...s/simp200W.gif

I actually happen to have a few TDA2030s in a box, hence the interest in this particular schematic. As far as I can tell it's a reasonably solid design. Can anyone spot any immediate problems with this design, or any simple and cheap improvements?

[pacificblue]

The transistors are probably BD707 and BD708, not KD.
According to the datasheet the TDA2030 is limited to 36 V supply voltage, not 44 V.

[NinjaKitten]

I actually spotted that last night whilst I was looking at the datasheet. I'll use a 30V supply.

As regards the power supply shown, would it not be a bit too noisy for audio purposes? I'd have expected to see an SMPS driving a circuit with this kind of amplification.

[sivan_and]

I think the 44volts is absolute maximum for TDA2030 A...version A is high voltage version

[NinjaKitten]

I know I'll need heatsinks for the transistors, but what about the opamps? Not sure what kind of thermal output I should be expecting.

[Stuart Easson]

Perhaps the 200w is peak, not rms

The power transistors mentioned will pop if you use more than a +/- 30v supply, they are rated 60v...

Most other parameters of the transistors are too small to get 200W from this arrangement, you will simply make nasty smelling smoke.

Fortunately the BD70x transistors are slow, so there is a good chance substituting other slow transistors that are appropriately rugged will get you closer to your goal...Adcom made the GFA1 that was a 'real' 200w RMS BTL amp, it used ~50v rails and 2SB554/2SD424 outputs. I have successfully substituted mj15003/4 to get a little more margin in current and power, seems like you could use them here.

The tda2030 will need to drive the base current of the outputs, to pretty much the full rail voltage, worst case maybe an amp or two. With 30v rails, at half power into 8 ohms, depending on the gain of the transistors the chip will be dissipating 5-10w. It will definitely need a heatsink for even short term operation.

HTH

Stuart

[NinjaKitten]

I'll swap the transistors for MJ15003/4s. Turns out the chips I have are indeed the TDA2030A's. A lucky break for me

As regards the power supply I'll see if I can knock up one that puts out around 40V. I'm actually waiting on delivery of a 75VA 230V primary, 2x 50V secondary transformer that was on sale for only £7.50 because one of the screw holes didn't get punched through when it was manufactured. The normal price is around £20. Bargain!

[pacificblue]

Which is of course not the transformer you will use for that amp, right?

[NinjaKitten]

Have I missed something? I was planning on building a simple power supply to run it off using that transformer. I don't see the issue.

Edit: Hmm... I think I calculated something incorrectly somewhere. For some reason my calculations say I can pull 15A from the primary without the transformer dying. Er, that's very wrong! I'm off out for a bit, then I'll fix my numbers.

[richie00boy]

Well let's see. 50V transformer (which will make approx 69V DC) with 44V absolute max chip. I can see the flames from here.