Electronics > Beginners

Loud Speaker?

<< < (15/18) > >>

ChrisGreece52:

--- Quote from: mariush on June 02, 2013, 01:15:31 am ---Yes, sounds about right.

A 24v transformer will have a peak DC voltage of 1.414 x 24v = 34v. With the drop in rectifiers, that's about 31v.

So +/- 15v is doable with a 24v center tap transformer and big capacitors on the output (let's say 2x3300-4700uF 25v on each side, negative and positive, so 4 capacitors in total ), or if you make the design in the datasheet that's with single power supply, about 8200-10000 uF 50v (in whatever capacitor combination you want, you can put capacitors in parallel to increase size)

A transformer rated for 24v AC rms 40-50VA would do.

See below for some examples

--- End quote ---
Got it :D but i could not find a proper power supply at ebay ....  :--

mariush:

--- Quote from: ChrisGreece52 on June 02, 2013, 07:27:55 am ---
Got it :D but i could not find a proper power supply at ebay ....  :--

--- End quote ---

You must really suck at searching then. from cheaper to more expensive

20VA : 2x24v or 1x48v with center tap (just connect the middle terminals)  - good for the third design in the picture a few posts above.20VA is a bit low but this is a cheap transformer.
http://www.ebay.com/itm/CTFC20-24-Camdenboss-Transformer-20Va-2-X-24V-/360622938744?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item53f6cd5a78   

50VA : 2x9v  or 1x18v with center tap.  Good for about +/- 11v so obviously less output power
http://www.ebay.com/itm/CTFC50-9-Camdenboss-Transformer-50Va-2X-9V-/130877005329?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1e78e09e11

50VA : 2x18v or 1x36v with center tap.  Good for the third design, just connect the middle terminals together.
You might be able to use it for first design (split supply) or second design, but you'd have to be really careful.   18v will give you a peak of about 26v, the bridge rectifier will drop about 1.5-2v so you're very close to the +/-25v absolute limit of the tda2050, if you ignore that the transformer may output 5-10-15% more at low loads.  You could put 2-3 big diodes on each output after the bridge rectifier, to drop the voltage about 2v more, so you'd have +/- 22-23v
http://www.ebay.com/itm/CTFC50-18-Camdenboss-Transformer-50Va-2X-18V-/130891176802?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1e79b8db62

50VA : 2x12v or 1x24 with center tap.  Exactly what you were searching for, this would give you +/-15v
http://www.ebay.com/itm/CTFC50-12-Camdenboss-Transformer-50Va-2X-12V-/130877006916?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1e78e0a444

100VA 2x24v or 1x48v  only for second or third design of power supply. Added because it's cheap for the VA rating and it's good enough to power 2-3 channels in case you want to make stereo or 2.1
for second design , connect the windings in parallel,   1 to 3 , 2 to 4, and you have a single 24v transformer with twice the current capability. use bridge rectifier and capacitors to get about +32v
for third design, connect 2 and 3  and you have a 48v with center tap, so third design will get you about the same +32-34v

http://www.ebay.com/itm/MCF-B19624F-Transformer-100Va-2-X-24V-/130877003135?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1e78e0957f

100VA 2x12v  or 1x24 with center tap. Exactly what you need, but enough VA for 2-3 identical amps
http://www.ebay.com/itm/CTFC100-12-Camdenboss-Transformer-100Va-2-X-12V-/360622945129?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item53f6cd7369

As a sidenote, this guy simply buys these transformers from Farnell and adds his fees then sells on eBay.
Farnell doesn't ship directly to Greece, but they have a distributor in your country:

Darlas Electronic Applications SA

5, Kimonos Str
122 44, Egaleo
Athens
Greece
Tel:    +30-210-59.86.179
Fax:    +30-210-59.11.161
Email:    darlas@darlas.gr
Web:    http://www.darlas.gr

They have an online store in which you can see the prices, for example here's the link to 86 pages of transformers to choose from : http://www.darlas.gr/comersus/store/comersus_listCategoriesAndProducts.asp?idCategory=17521983
And if you search by product name, for example CTFC50-12 for the 2x12v 50VA transformer that matches your needs, you can find it at 20 euro on their site: http://www.darlas.gr/comersus/store/comersus_viewItem.asp?idProduct=1890021

You can go on farnell.com to the transformers category :  http://uk.farnell.com/isolation

Use the filters there to select  2x12v, 2x15v, maybe even 2x10v (this should give you about +/-13v) , maybe also check 24v,30v,32v (they may have center tap but you only see if you check datasheet),  maybe also check 2x18v if you may change your mind and do single power supply (third design)

select minimum VA rating 20va, maximum 100-150va, then look in the results and find something you like. Get the product code and enter it on darlas.gr site in the search box to see how much it costs for that store to get it for you.

ChrisGreece52:

--- Quote from: mariush on June 02, 2013, 02:20:53 pm ---
--- Quote from: ChrisGreece52 on June 02, 2013, 07:27:55 am ---
Got it :D but i could not find a proper power supply at ebay ....  :--

--- End quote ---

You must really suck at searching then. from cheaper to more expensive


As a sidenote, this guy simply buys these transformers from Farnell and adds his fees then sells on eBay.
Farnell doesn't ship directly to Greece, but they have a distributor in your country:

Darlas Electronic Applications SA

5, Kimonos Str
122 44, Egaleo
Athens
Greece
Tel:    +30-210-59.86.179
Fax:    +30-210-59.11.161
Email:    darlas@darlas.gr
Web:    http://www.darlas.gr

They have an online store in which you can see the prices, for example here's the link to 86 pages of transformers to choose from : http://www.darlas.gr/comersus/store/comersus_listCategoriesAndProducts.asp?idCategory=17521983
And if you search by product name, for example CTFC50-12 for the 2x12v 50VA transformer that matches your needs, you can find it at 20 euro on their site: http://www.darlas.gr/comersus/store/comersus_viewItem.asp?idProduct=1890021

You can go on farnell.com to the transformers category :  http://uk.farnell.com/isolation

Use the filters there to select  2x12v, 2x15v, maybe even 2x10v (this should give you about +/-13v) , maybe also check 24v,30v,32v (they may have center tap but you only see if you check datasheet),  maybe also check 2x18v if you may change your mind and do single power supply (third design)

select minimum VA rating 20va, maximum 100-150va, then look in the results and find something you like. Get the product code and enter it on darlas.gr site in the search box to see how much it costs for that store to get it for you.

--- End quote ---
Thanks for your suggestions.
First i do not suck i was just searching for the wrong thing :D i searched for 30 volt 1.5 amp power supply ( and to be sure i did this because 30 1.5 = 45 watts 24 for the amp and the rest will be dissipated as heat :P )
Also thanks for your suggestions they are pretty good
but i an not familiar with tranformers (at a wide range).
But i could make this work :)
Second thing : the prices a re excellent and thanks for your consideration :D
and finally third i have checked out the darlas store and i have 2 comments
1 : most of the things that it sells are overpriced
2:shipping from Athens to Kavala is more expensive than some buyers UK products.

madires:

--- Quote from: ChrisGreece52 on June 02, 2013, 07:26:07 am ---I will get something from the above ones i was thinking about the first one.
And of course middle.
But shall i use thermal paste?? (like in a CPU for better heat transmision)

--- End quote ---

Yep! If you need isolation add a mica plate or use a sil-pad without the thermal paste. Also use an isolation thingie for the screw. You could mount a large flat heatsink at the backside of your speakers box. Make a matching cutout in the backside, of course a little bit smaller than the heatsink to get an overlapping area for adding a sealing tape and bolting down the heatsink. That's the standard way for active speakers.

mariush:

Yes, you need to have good contact between the tda2050 and the heatsink. cpu paste would probably be easiest for you to get access to and works great.

The tab on tda2050 (the large metal backside) is connected to pin 3,  which is -Vs  (negative voltage) when you use split power supply. If you use single power supply version, -Vs is basically ground.
Since you use transformer, the outputs -Vs and Vs are floating, so it's not a problem that the whole heatsink will stay at -Vs, you won't get electrocuted.
You just have to make sure the heatsink doesn't connect to ground somehow. For example, if you plan to put this in a metal box, make sure the heatsink doesn't touch the metal case.

If you don't want to worry about it and have the heatsink isolated from the tda2050 (to screw it on a metal case for example to enlarge its size using the metal of the case), then you must insulate the back of the chip from the heatsink.
There are ready made pads (rectangles of a certain material) which are good for thermal transfer, and you don't need cpu paste with those.
Depending on the material they insulate the metal of the chip from the heatsink, or they don't. One pad called sil-pad does insulate:

ex : http://uk.farnell.com/bergquist/2015-54/sil-pad-2000-015-to-220/dp/681118

Same with mica based pads:

http://uk.farnell.com/multicomp/mk3306/insulating-kit-mica-to-220/dp/520214

But just using a pad is not enough, you also have to insulate the screw going through the heatsink... there is a type of plastic ring that goes into the hole on the tda2050 that guides the screw so it never touches the metal. You can see one of those plastic thingies in the link above.

You can find all of the above on ebay but be careful because these are generally in a standard shape, either for to-3, to220, to247 and your tda2050 is in pentawatt size, which is a bit larger so you probably won't find these cheap insulators but rather only larger pads from which you can cut exactly the size you want.

Overall I'd say it's not worth it, should be easy to just make the heatsink not touch anything, in the worst case scenario just put it on some nylon spacers like these, which you could also find on ebay or in old computer cases ...

http://uk.farnell.com/duratool/d01455/pcb-spacer-support-nylon66-natural/dp/1733383
http://uk.farnell.com/duratool/d01472/pcb-spacer-support-nylon66-natural/dp/1733402
http://uk.farnell.com/duratool/d01470/pcb-spacer-support-nylon66-natural/dp/1733399

or you could also just get some electricians tape and put several layers of tape where the heatsink might touch if it flexes, bends etc

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod