Help with creating a power supply

[pyrohaz1]

Hey guys, im wanting to create a Bass amplifier head and for the amplifier section, I want to use the Philips TDA8920BTH, it can provide quite a high amount of power at 0.5% distortion in BTL mode. What I was wondering though was how do I create a mammoth PSU for this amplifier? I would have liked to use a switching power supply to reduce the weight of the head but if a transformer based one would be best, could you advise me on what would be required and how to make it? Thanks

Amplifier: http://cgi.ebay.co.uk/Classic-D-philips-TDA8920BTH-digital-amplifier-2-100w_W0QQitemZ150446744622QQcategoryZ14973QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DDLSL%252BSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BIEW%252BFICS%252BUFI%26otn%3D8%26pmod%3D150436324792%252B150436324792%26po%3D%26ps%3D63%26clkid%3D8209590715140814741

PDF: http://www.nxp.com/documents/data_sheet/TDA8920B.pdf

Sorry about the long URL's, I forgot how to shorten them XD

 

[Hero999]

Firstly, ave you asked the supplier?

Have you looked at using two laptop power supplies connected in series to make a +/-24V supply?

You need to make sure the output voltage and power is enough, here are a couple I found on eBay which will probably do.

http://cgi.ebay.co.uk/SWITCHED-MODE-LAPTOP-POWER-SUPPLY-5-6A-15V-24V-120W-/160438733975?cmd=ViewItem&pt=UK_Computing_LaptopAccessories_PowerSupplies&hash=item255ae4cc97

http://cgi.ebay.co.uk/120W-15-24V-Universal-Laptop-Power-Supply-Dell-acer-IBM-/370376063396?cmd=ViewItem&pt=UK_Computing_LaptopAccessories_PowerSupplies&hash=item563c2239a4

 

[pyrohaz1]

Thank you very much for your help as usual hero I would have asked the seller but after buying various items multiple times from China, the outcome is usually the same: Read the description. So instead, I looked through his shop and found a power supply section but I wasn't able to find a suitable pair or one . After doing some further browsing on eBay, I found a new revision of that board that accepts a Tapped transformer (20v, 0v, -20v) so I was just thinking, get an 18v, 0v, 18v Torroid, shove a switch and correctly measured fuse in the AC side and then be done with it? I'm just not sure on the VA rating I would need. Could you help me there please?

Thanks guys

 

[Hero999]

A transformer with two 18V secondaries can be used. Connect the two secondaries in series to form a centre tap and connect to a brdge rectifier and two large capacitors to the centre tap.

Here's an exmaple:

The capacitors need to be very large >10,000μF 35V.

The transformer can be 200VA which is slightly underrated but that doesn't matter as the amplifier won't draw full power continuously.

To be honest, I think it's probably less trouble to go with the lap top power supplies which will be less bulky and you can still put them in your own enclosure, if you like.

 

[pyrohaz1]

I completely agree with your laptop power supply statement, after a quick look on Rapid for a transformer (18v split at 250VA), a hefty

 

[Hero999]

The laptop PSU you've linked to isn't powerful enough, the amplifier has an output capacity of 100W per channel @ 90% efficiency (220W total) so you need two power supplies capable of at least 110W each which is why I searched eBay for 120W laptop power supplies.

The pre-amp will depend on what you wan to connect the amplifier to.

 

[pyrohaz1]

Your absolutely correct there! Sorry. Yep two 120w Laptop power supplies it is then! I'm no longer able to make PCB's at school (Because I don't go there anymore!) Do you know where I can get single PCB's fabricated for suitable prices? OR kits that I can use (without a laser printer as I simply cannot afford one ) I think it would probably be better to design my own preamp to fit the specification of my amplifier instead of buying a prebuilt one. Also, I can customise it to my power supply.

 

[Hero999]

You shoudn't need a PCB for this circuit.

I use toner transfer to do most of my PCBs but the photo method is higher quality.

You'll need a laser printer or access to a photocopier for toner transfer. It's easy, print the design, iron on to the board, soak in water until the paper peels of leaving the toner fixed to the board and etch in the usual manner. You can buy special proprietary papers but normal printer paper will also work, I've found glossy magazine paper is best. You'll need a bit of practise to perfect the technique and get the right iron temperature, too cool and the toner won't stick, too hot and it'll smear. Make sure the PCB is clean before you start and remove the toner with wire wool and soap before soldering.