DIY 2.1 amplifier  - Page 1
Forum section: electronics / projects

author: seanhaz
author_rank: Contributor
timestamp: October 31, 2013, 06:23:54 am
content: hey, i got myself one of these cheap diy amplifiershttp://www.aliexpress.com/item/TDA2030A-2-1-Stereo-Audio-Amp-2-Channel-Amplifier-Subwoofer-Amplifier-Board/877442168.htmlnow im trying to find the right transformer for it, im a bit confused on the whole dual 12v supply thing, can i just use a dual 12v output transformer? or does it need to be like a 24v overall on the secondary output with a center tap as the "ground" so its 12v either side of "ground"Thanks

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 31, 2013, 07:09:59 am
content: Quote from: seanhaz on October 31, 2013, 06:23:54 amUsing a dual 12V transformer is perfectly fine, if you connect it properly. Two of the secondary leads should be connected together to create the 'ground' ('center tap') for your PCB, that is all it takes. You need to wire it up such that you get 24V AC across the pair of 12V connections, then everything else will work out right. You can measure this out of circuit, if you wish to check the phasing before connecting the transformer to the amplifier board.If you have the datasheet for the transformer, then notice the phasing dots on the schematic overview. Connect one secondary lead with a dot to one without to create 'ground'. Then the two remaining leads are your pair of 12V connections.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: October 31, 2013, 07:20:21 am
content: The amplifier ICs on that board are rated for +-6 to +-22volts...So you can really use a transformer from about 10volts centre tapped (5volts per input) to 36volts centre tapped....Not sure what your budget is, but this would happily run it quite well: (its actually somewhat bigger than you need, but bigger is better, right?)http://secure.oatleyelectronics.com//product_info.php?cPath=29&products_id=939&osCsid=fgoe5c8jg350sniuvdos44i091And don't forget a heatsink!

author: mariush
author_rank: Super Contributor
timestamp: October 31, 2013, 07:30:11 am
content: Uhmm... yeah, tda2030a DOES indeed accept voltages from +/- 6v to +/- 22v as the datasheet says:http://www.st.com/web/en/resource/technical/document/datasheet/CD00000129.pdfBut be aware that the chip likes higher voltages.. as +/- 6v you'll barely get a couple of watts out of it.And no, I wouldn't recommend a 36v centre/center tapped because that would give you about +/- 18v AC rms, which gives you peaks of about 25v, minus a diode drop of about 1v .. so about 24v, which is more than the maximum of 22v recommended.Even a 32v transformer would be risky because at low currents, the transformer may give up to 5-15% more voltage so again, you will exceed the +/- 22v spec of the chips.I'd recommend sticking to let's say a maximum of 28v AC rms with center tap. 24v will be fine though.And be careful with the VA rating of the transformer. The ICs are about 70% efficient, so if you want ... let's say 10w per channel and 20w for subwoofer, that's 40w in total but due to the poor efficiency you'll use about 50 watts of actual power, 10 watts will be turned to heat.So you have a 24v AC RMS transformer ... 50 watts of power, therefore you'd need a transformer rated for about 60-75VA to get this. If you want to be able to get the max of 18w per channel and 36w for subwoofer, you're looking at 100-120VA rated transformer.You can use cheaper transformers, for example rated for 20-40VA if you won't turn the volume that high or you will have smaller speakers connected to it.Heatsink is super important for those 2030A ... as I already mentioned due to low efficiency they will heat up quite well. They MUST be heatsinked.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: October 31, 2013, 07:52:42 am
content: I wasn't going to bother working out exact voltages :p12v ac, makes about +-16volt rails, should be good for about 12watts into 8ohm, or 18watts into 4ohmBut, the way the two ICS are linked for the "subwoofer" channel, means you can only run 8ohms minimum, so keep that in mind when choosing the "sub"

author: seanhaz
author_rank: Contributor
timestamp: October 31, 2013, 08:02:33 am
content: awesome, thank you all for the great info!

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 31, 2013, 08:12:31 am
content: Quote from: AmmoJammo on October 31, 2013, 07:52:42 amYou probably should, before giving component destroying advice.Besides, 'working this out' in your head on the fly should take about ... 0.3s or so?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: October 31, 2013, 08:17:59 am
content: Quote from: ElectroIrradiator on October 31, 2013, 08:12:31 amI did... 18volts ac = close enough.If I'd linked him to a 36 volt centre tapped transformer, THEN I could understand you having a cry