Loud Speaker?

[madires]

thats the first thing i came up when i searched 12 volt 3 amp
http://www.ebay.com/itm/36W-12V-AC-DC-Power-Supply-3-Amp-12-Volt-Adapter-LCD-3A-Charger-Laptop-5-5-2-5mm-/270881755391?pt=AU_Laptop_Accessories&hash=item3f11cf90ff
does it worth it or it will be crappy ?

Better stay away from SMPSUs. Mariush suggested a 24V transformer, I second that. 24V 50VA should be a good choice.

[IanB]

Let's be realistic now. How much sound do you need to practice guitar with? It's all very well talking about 15 W, 25 W, etc, but that's a lot! As I mentioned before, battery powered radios can easily fill a room with sound, and there is no way you can get 15 W out of some little alkaline batteries.

Yes, a proper big hi-fi amp might need a big heavy transformer, but a little practice amp as a first electronics project? I think we need to get down to earth here.

[ChrisGreece52]

Let's be realistic now. How much sound do you need to practice guitar with? It's all very well talking about 15 W, 25 W, etc, but that's a lot! As I mentioned before, battery powered radios can easily fill a room with sound, and there is no way you can get 15 W out of some little alkaline batteries.

Yes, a proper big hi-fi amp might need a big heavy transformer, but a little practice amp as a first electronics project? I think we need to get down to earth here.

Right i am sorry but i am figuring this out as i am going through ...... so we have new specs
NON portable
singe or dual signal
loud but not SO loud (medium sized room medium noise level.
Taking into account all the things you suggested above i wont need something more powerfull than 25 watts so we have that limit .
With this in mind i am looking for a power supply that it can output up to 30 watts (5 watts will be lost as heat right  ? )

[madires]

Let's be realistic now. How much sound do you need to practice guitar with? It's all very well talking about 15 W, 25 W, etc, but that's a lot! As I mentioned before, battery powered radios can easily fill a room with sound, and there is no way you can get 15 W out of some little alkaline batteries.

Yes, a proper big hi-fi amp might need a big heavy transformer, but a little practice amp as a first electronics project? I think we need to get down to earth here.

A decent guitar amp has got about 15-30W and a quite large case (large speaker). If you want to keep the guitar amp small, i.e. using a smaller speaker, you'll need more power to compensate the size reduction. A big HiFi amp got much more power to be able to deliver a large dynamic range as required for listening to classic music. If you're looking for simplicity for a beginner there's not much difference between 5W or 150W, tons of inexpensive and simple amp ICs and modules are available. 

[madires]

Right i am sorry but i am figuring this out as i am going through ...... so we have new specs
NON portable
singe or dual signal
loud but not SO loud (medium sized room medium noise level.
Taking into account all the things you suggested above i wont need something more powerfull than 25 watts so we have that limit .
With this in mind i am looking for a power supply that it can output up to 30 watts (5 watts will be lost as heat right  ? )

30W power in and 20W audio out should be fine.

[ChrisGreece52]

Let's be realistic now. How much sound do you need to practice guitar with? It's all very well talking about 15 W, 25 W, etc, but that's a lot! As I mentioned before, battery powered radios can easily fill a room with sound, and there is no way you can get 15 W out of some little alkaline batteries.

Yes, a proper big hi-fi amp might need a big heavy transformer, but a little practice amp as a first electronics project? I think we need to get down to earth here.

A decent guitar amp has got about 15-30W and a quite large case (large speaker). If you want to keep the guitar amp small, i.e. using a smaller speaker, you'll need more power to compensate the size reduction. A big HiFi amp got much more power to be able to deliver a large dynamic range as required for listening to classic music. If you're looking for simplicity for a beginner there's not much difference between 5W or 150W, tons of inexpensive and simple amp ICs and modules are available.

Excactly i am looking for something basic but with ass little distortion as i can get ... :S

[IanB]

Excactly i am looking for something basic but with ass little distortion as i can get ... :S

You know guitar amps are commonly designed to add distortion, right? (Albeit nice distortion, not horrible distortion...)

[mariush]

ok but 30 watts??? thats sounds a lot ....
if i could find a transformer 12 volt it had to be 2.5 amps ... thats easy to find right if i buy a 12 volt 3 amp power supply it would be more than enough to power it on !!!

thats the first thing i came up when i searched 12 volt 3 amp
http://www.ebay.com/itm/36W-12V-AC-DC-Power-Supply-3-Amp-12-Volt-Adapter-LCD-3A-Charger-Laptop-5-5-2-5mm-/270881755391?pt=AU_Laptop_Accessories&hash=item3f11cf90ff
does it worth it or it will be crappy ?

MY GOD ..

I went through this 3 or 4 times already in this thread 



12 V DC  =  +/- 6 V  (±Vs) ====>  2-3 audio watts

It's pointless to get a 12v transformer even if it's rated for 2.5A because the tda2050 WILL NOT USE THE CURRENT it has available.  It can only output 2-3 watts at that voltage.
You can use an ATX power supply with 40 Amps on 12v and it would still only make only 2-3 watts of audio.

YOU NEED LARGE VOLTAGE

A 24 V AC transformer will give you when rectifier 24 x 1.414  = 33.9v. With diode drops, you have 32V which is below the maximum of 50V the chip supports.   32 V  DC = +/- 16v so on the graph that shows you it the amplifier will output about 13-15 audio watts there.
13-15 watts of audio is enough for a room and on par with the speakers you have.   
To get about 13-15 watts of audio, the amplifier will waste about half of that as heat, so it would use about 20 watts. 

madires told you that you can get up to 32 watts from this TDA2050 chip, but ONLY if it receives about 45-48 volts (close the maximum of 50v it supports).  You can see that on the graph above. The output power has a direct relation with the input voltage.

A 24v AC 20VA will be enough for ONE CHANNEL (mono), 15 watts of audio max.  If you'll want stereo, you make two copies of the amplifier and get a 40VA transformer or better.

I only told you about 12v in the first posts because it's a common voltage you have in your computer power supply so when making an amplifier, you could just connect it to the computer power supply and test it. This way you'd only get 2-3 watts of audio. After that, you could just get a big transformer when you have money (or when you find one), and then you have big output.

[ChrisGreece52]

Excactly i am looking for something basic but with ass little distortion as i can get ... :S

You know guitar amps are commonly designed to add distortion, right? (Albeit nice distortion, not horrible distortion...)

some nice distortion effect activated by a switch would be fine but its a bass guitar so it would not be vital but pretty fun to have

[ChrisGreece52]

ok but 30 watts??? thats sounds a lot ....
if i could find a transformer 12 volt it had to be 2.5 amps ... thats easy to find right if i buy a 12 volt 3 amp power supply it would be more than enough to power it on !!!

thats the first thing i came up when i searched 12 volt 3 amp
http://www.ebay.com/itm/36W-12V-AC-DC-Power-Supply-3-Amp-12-Volt-Adapter-LCD-3A-Charger-Laptop-5-5-2-5mm-/270881755391?pt=AU_Laptop_Accessories&hash=item3f11cf90ff
does it worth it or it will be crappy ?

12 V DC  =  +/- 6 V  (±Vs) ====>  2-3 audio watts

It's pointless to get a 12v transformer even if it's rated for 2.5A because the tda2050 WILL NOT USE THE CURRENT it has available.  It can only output 2-3 watts at that voltage.
You can use an ATX power supply with 40 Amps on 12v and it would still only make only 2-3 watts of audio.

YOU NEED LARGE VOLTAGE

I forgot about that to be honest sorry

[madires]

Excactly i am looking for something basic but with ass little distortion as i can get ... :S

You know guitar amps are commonly designed to add distortion, right? (Albeit nice distortion, not horrible distortion...)

Either you go for a tube amp or get a guitar pedal for that :-) There isn't any nice distortion with a modern amp. But you can add a "nice distortion" effect in the preamp-stages of the guitar amp. That's the common way used by most guitar amps.

[madires]

YOU NEED LARGE VOLTAGE

I forgot about that to be honest sorry

If you have no constraints for the PSU use higher voltages and split voltages (+/-), based on the amp IC or module you're using. If you have to use 12V go for a car audio amp IC, which is optimized to deliver more power at that low voltage. But use linear PSUs, no SMPSUs, because those give you a headache. They're much cheaper, but you have to add a lot of filtering (large and expensive parts) to make them usable for audio amps.

Back to Watts. For a bass guitar you obviously want to have a guitar amp with good bass. The first thing to consider is the human ear (see dBA http://en.wikipedia.org/wiki/A-weighting). There's a huge difference in loudness if listening to 1W audio with 1kHz or 100Hz. IanBs transistor radio with a decent speaker works fine for a midsized room as long as the audio is in the kHz range. But if you go down with the frequency you have to provide much more power to achieve the same loudness as the 1kHz signal got. Therefore you need a large speaker capable of providing a good frequency response down to the 30Hz you like to have. And you need some Watts to drive that speaker and to compensate for the dBs the speaker can't deliver and the dBA concept. If you use a more small-ish speaker you'll need more Watts and an adjustable bass booster. The latter would be a good idea anyway, also for a large speaker. And for audio mostly in the bass range a slighty oversized PSU is desirable, because a overdriven PSU doesn't let the amp give you nice bass. If you want 30W audio use an amp with >=50W. It's a bad idea to max out the power specs of the amp (increased distortion, bad sound and so on). That's all basic audio 101.

[SeanB]

Distortion is easy, LM386 run till it clips.............

Or 2 back to back diodes and a low value series resistor with about 2Vpp of signal works as well.

[ChrisGreece52]

Distortion is easy, LM386 run till it clips.............

Or 2 back to back diodes and a low value series resistor with about 2Vpp of signal works as well.

yeah but lm386 is a crappy amp so i need something with more power.

[madires]

Distortion is easy, LM386 run till it clips.............

Or 2 back to back diodes and a low value series resistor with about 2Vpp of signal works as well.

yeah but lm386 is a crappy amp so i need something with more power.

I think he meant that you could use the LM386 as a preamp stage just to generate the distortion.

[ChrisGreece52]

Distortion is easy, LM386 run till it clips.............

Or 2 back to back diodes and a low value series resistor with about 2Vpp of signal works as well.

yeah but lm386 is a crappy amp so i need something with more power.

I think he meant that you could use the LM386 as a preamp stage just to generate the distortion.

oohhh ok ... but why should i use lm386 as a preamp for distortion while i can just change the value resistors i can use to change the gain (that is what i mean by distortion it may be wrong.)

[ChrisGreece52]

So finally after all i learned i want to go with something outputs 30 volts (15 +/- )watts thats the best state ( distortion wise) but i can not find a transformer suitable for the application)
At 24 watts my goal (output power )
the chip will dissipate 14 watts of heat
so i need something that outputs (24+14 =38) 38 watts
from the formula that i saw in an answer we have P = V I so I = P/V => I = 38/30 = 1.266 Amps (pretty good  and achievable)
I posted this so i make sure that i wont screw the calculations up
Thank you
 Datasheet :
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXyuqt.pdf

[mariush]

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

[mariush]

And don't forget about the heatsink.

At low volumes, it won't waste that much power, but if you get it going at high output, it will waste 10-15w of power.
Tiny heatsinks don't work, like the datasheet says you need a relatively big heatsink (compared to what you may be used to) with low thermal resistance.

Either screw it on a CPU heatsink with the cpu fan running at low speed, or get a large heatsink like the one in this picture:

http://www.ebay.com/itm/100x55x10mm-Aluminum-Heatsink-for-Electronics-Computer-Electric-equipment-H104-/171015086436?pt=LH_DefaultDomain_0&hash=item27d14b2164
http://www.ebay.com/itm/100x55x10mm-Aluminum-Heatsink-for-Electronics-Computer-Electric-equipment-H104-/200801981466?pt=LH_DefaultDomain_0&hash=item2ec0bb141a
http://www.ebay.com/itm/100-45-10mm-Aluminum-Heat-Sink-TO-220-w-o-stand-for-LED-Power-IC-Transistor-/260865037352?pt=LH_DefaultDomain_0&hash=item3cbcc49428
http://www.ebay.com/itm/100x35x10mm-High-Quality-Aluminum-Heat-Sink-For-Computer-Electronic-H62-/181110957180?pt=LH_DefaultDomain_0&hash=item2a2b0de47c
http://www.ebay.com/itm/100x35x10mm-High-Quality-Aluminum-Heat-Sink-For-Computer-Electronic-H62-/190808608538?pt=LH_DefaultDomain_0&hash=item2c6d144f1a


If you get something like the above, you must screw the chip somewhere close to the middle of the heatsink, not on the side.  Don't forget to use some cpu thermal paste between heatsink and the chip.

[ChrisGreece52]

And don't forget about the heatsink.

At low volumes, it won't waste that much power, but if you get it going at high output, it will waste 10-15w of power.
Tiny heatsinks don't work, like the datasheet says you need a relatively big heatsink (compared to what you may be used to) with low thermal resistance.

If you get something like the above, you must screw the chip somewhere close to the middle of the heatsink, not on the side.  Don't forget to use some cpu thermal paste between heatsink and the chip.

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)

[ChrisGreece52]

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

Got it but i could not find a proper power supply at ebay .... 

[mariush]

Got it but i could not find a proper power supply at ebay .... 

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]

Got it but i could not find a proper power supply at ebay .... 

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.

Thanks for your suggestions.
First i do not suck i was just searching for the wrong thing 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 )
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
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]

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)

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