Loud Speaker?

[ChrisGreece52]

Thank you all but i am confused.... i had not so many time to read in depth all the comments but here are some things that will make you life easier
My supply will be a 12 volt 1 amp ac to dc converter
I only need 1 channel (left or right ) or even both no prob.
I need adjustable gain with caps or resistors
I need it to be loud but no so easily distorted
As for heat dissipation its ok ill use a big ass heatshink or even combine a small heatshink with a fan for maximun cooldown

Ok, Chris, here's a very basic explanation.

Amplifiers output a certain amount of power (in watts) based on the resistance of the speakers ( in your case 8 ohms) and the input voltage they receive (and the current, naturally).  Some audio amplifiers aren't that sensitive to input voltage, others are. 

These amplifier chips that I mentioned (tda2040, tda2050) like bigger voltages a lot, the more voltage the more audio power they can output. With these amplifier chips, as you can see in the graph above, the power output increases quite a lot as you increase the input voltage... with +/-5v (10v with single power supply) you only get 2-3 watts, with +/-22v (44v with single power supply) you get 25-30 audio watts (ten times as much).

Other amplifier chips like the TDA1519 mentioned by madires only works with a smaller range of voltages and is a bit more efficient with lower voltages, but as a downside it can't give you as much power as the previous chips - it tops out at about 5-6 watts while the tda2050 can do about 20-25 watts.

The amplifier chips that can output a lot of power are usually designed to be used with split power supply. That is, you have a transformer with two secondary windings or a single winding with a center tap, and from that you can create a negative voltage and a positive voltage, so they amplifier has two input voltages, like this:



From top to bottom, you have at the output +V , GND and -V
In the picture above, you have a transformer that outputs 48V AC with a center tap - the center tap becomes the ground, and there's a positive 24v AC and a negative 24v AC. These are RMS values, so when converted using a bridge rectifier like in the pictures, you get about 34v.  So that is a +/- 34v split power supply.
The TDA2050 can handle a maximum of +/- 25v  so this transformer is actually too big for it, but it's just an example.

Split power supply is better for audio amplifier chips because it makes it easier for an audio amplifier to create the audio waves that are sent to the speakers.

Single power supply is the power supply like you have on the computer or on ac to dc adapters, where you have just ground and a positive voltage. 
Some amplifier chips can work with just positive voltage but when using such power supply you have to keep in mind that the voltage difference is now half compared to a split power supply.  12v DC  is equivalent to -6 - 0 - +6v split power supply because from -6 to +6 is a potential difference of 12v.
So wherever you look in graphs made for split power supplies, you have to look at the values for half the voltage for your single power supply.

Now, as the amplifier chip no longer has that positive and negative voltage, the output is harder to generate and it's a bit hard to explain but in such configuration a large capacitor is needed in front of the speaker - if you look in the datasheet for TDA2050 you will see the "single power supply" design has a 1000uF capacitor near the speaker while the split power supply doesn't need one. The TDA1519 works around this issue in BTL mode by making both audio amplifiers in the package work like a single amplifier so in that mode, the audio chip needs two speakers connected for each channel.

Going back to your original problem. 

You have a 12v 1A ac to dc adapter.  The power this adapter can deliver to some device is determined by the formula  Power = Current x Voltage so the power for this adapter is P = 12v x 1 = 12 watts.

An ideal amplifier would take these 12 watts of power and produce 12 watts of audio power.
However, you have to understand that audio amplifiers are not ideal, and depending on their type,and they're not very efficient. The amplifier chips we're talking about here are class AB amplifiers, which usually are about 60-70% efficient.
But as you can see from that graph I showed you, with 12v input, the amplifier chip can only produce 2-3 watts of audio power without causing a lot of distortion, it just doesn't "like" such low voltages.
So you give it 12v, but produces about 3 audio watts. It probably has about 50% efficiency so the tda2050 probably uses about 6 watts out of those 12 watts you make available, the rest are unused.  If you make two amplifiers, one for each channel, both chips will use in total 12 watts or more, so your 12v 1A ac to dc adapter is to the limit.

I originally told you about 12v because computer power supplies have 12v, so it would be easy to get a used power supply from a computer or just power the audio amplifier from your computer.

But keep in mind, even if you connect it to a power supply that outputs 12v and may output 20-30 A on 12v (250-400w), the audio amplifier chips won't use this power, because they don't like such low voltages, they'll still only use about 6-10 watts.

The beauty of these chips is that you use vo properly rated capacitors (with big voltage rating) you can power these audio chips from 12v and get only 3 audio watts in speakers and when you find a transformer you can replace the 12v with the output of that transformer and get lots of audio watts.

For example, let's say you find somewhere a 24v AC rms transformer rated for 50 VA (a new one costs about 15-20$, on eBay they're cheaper but shipping to Greece costs anyway money).  When converted to DC, that 24v AC rms becomes about 32 volts.  The total power of the transformer is 50VA, you can equal that to 50 watts.

If you go and look on that graph, 32V DC from a single power supply is equal to about +/- 16 V so the TDA2050 could produce about 13-14 audio watts in the speaker. Now keep in mind the amplifier chip is about 60-70% efficient, so to produce those 13-14w of audio power, the amplifier "eats" about 4-6 watts and wastes it as heat, so in total the amplifier chip uses about 20w out of those 50w the transformer can give.

So even though the transformer makes 50 watts available, a single tda2050 would use only about 20 watts.  That's great, because you want stereo, so you basically have two identical circuits and in total, the two amplifier chips would use about 40 watts, which is below the 50 watts the transformer is capable of.
 
The gain of the amplifier... normally, you don't mess about with it, you just set it to a reasonable value (the one recommended in the datasheet and mentioned on that website with hi-fi amp based on tda2050) is a good one. You can always adjust the volume from your sound card. Either way, you can adjust that quite easily on a lot of amplifier chips.
The LM386 probably needs one because it distorts a lot otherwise... the lm386 is lousy for powering speakers like the ones you say you have.

Thank you so much for the information you provided me with ... but still the question remains... what chip you work the best i could search for other transformers on ebay to power the amp but i also have a 9 volt transformer (i know nothing great ) but i think it has 1 primary and one secondary winding on it .
Anyway ill post 2 pics of it and ill read again your answer in case some info went unseen thank you so much

Edit : i forgot to add the pics the first time

[mariush]

Wtf ... why quote my whole post for just two-three lines of text?!

Oh man.... you're thick. 

No chip from the ones above would work best, because there are other chips that are more efficient and with less distortions. But considering you're a beginner, because the parts are easy to find, because it's easy to make the circuit even on a prototyping board, that's why I recommended you that TDA2040 or TDA2050. They're very easy for a beginner. So go with those.

I explained in that post exactly what transformer you'd need, or what power supply to use.
Some chips can work with low voltage, so they'll need current (amps) to output the audio watts they say they can do.  ex TDA1519b mentioned only goes up to 18v but does about 12w (2x6w) with that.
Other chips are designed to work with higher voltage but can also work at some low voltage with reduced number of audio watts. The TDA2050 works as low as 10v and as much as 50v, but at 10v it only outputs 2-3 audio watts.

The transformer you show in pictures is for 9v... isn't it obvious from my previous comments that it won't be good since TDA2050 can only work from 10v ( or +/-5v,  as in split power supply -5v, ground, +5v)
Next, I explained already that the amplifier needs an amount of watts to go in it, to output a number of audio watts.
Look at the damn plastic case the transformer came in, you will see it says something like  9v 300mA ... that's 9v  0.3 A ... the power would then be 9 * 0.3A = 2.7w. Even if the tda2050 could run at 9v, how many audio watts do you think it could output if you only give it 2.7 watts to play with and the chip is about 50% efficient with such low voltage? I went through all those explanations only to go over your head... damn.

That transformer in the pictures is very small, it's 300mA maximum. You can't do shit with it when it comes to audio amplifiers.

Look for something in the range of 18v (either with center tap or two 9v secondary windings)  or a 24v transformer.
Popular values are  12v,15v,18v,20v,24v, 2x9 , 2x10, 2x12, 2x15, 2x18v, 2x20v, 2x24 (if they're separate windings you can use the windings in parallel to have 24v ac at twice the current). The tda2050 can work at up to 50v or +/- 25v so in split power supply you could use up to 2x18v and in single power supply you could use up to 24v AC or a transformer with 2x15v in series.

 Look for a rating of at least 40VA. if it doesn't say an amount in VA, it should say amps ... 40 VA / 24v = 1.6A ... look for anything above 1.5A or 40VA.
Such transformer would be heavy, about 1 Kg, here's some examples of transformers that would work for two separate tda2050 (so you have stereo) : http://goo.gl/MxAjM
Look at the pictures to get an idea of size, look at details to see the weight, look at datasheet if you want... smallest (in voltage) selected there is with 2 12v secondaries which can be linked together to give you 24v AC rms, which when is converted to DC gets you about 32 V DC which is good enough for a lot of audio watts.
The cheapest there is even better with 2x15v dc, you could make even the split power supply version of the amplifier and it would give a lot of power.

Alternatively, you can get a 24v power supply, which may be cheaper:
http://www.ebay.com/itm/AC-220V-to-DC-24V-3A-72W-Switch-Power-Supply-Transformer-for-LED-Illuminated-/360525805977?pt=AU_B_I_Electrical_Test_Equipment&hash=item53f1033999
http://www.ebay.com/itm/AC-220V-to-DC-24V-3A-72W-Switch-Power-Supply-Transformer-for-LED-Illuminated-/380532239639?pt=AU_B_I_Electrical_Test_Equipment&hash=item58997d2d17

9 volt transformer (i know nothing great ) but i think it has 1 primary and one secondary winding on it .

Of course it has one primary and one secondary, otherwise it wouldn't be a transformer, it would be a choke, or inductor. 
Like I said, if it's only one secondary  you can do the single power supply design, if you have two windings you have the option to do the split power supply or just connect the two windings in series to get one single big winding and do the single power supply design.

[IanB]

Chris: a key thing is what do you want to do with this amplifier? What is your input source? What is the listening environment? A tiny speaker with low power can easily be enough to listen to in a quiet room. If you want a lot of sound you will need bigger speakers to go with the bigger amplifier. Tiny speakers will just sound tinny at high volumes.

[ChrisGreece52]

Chris: a key thing is what do you want to do with this amplifier? What is your input source? What is the listening environment? A tiny speaker with low power can easily be enough to listen to in a quiet room. If you want a lot of sound you will need bigger speakers to go with the bigger amplifier. Tiny speakers will just sound tinny at high volumes.

Well you are right i left this info out of the conversation for good.
This amp will be made for medium sized, and not so quiet room.
Ill be using it with my bass guitar and i am planning on using small to medium sized speakers with a wooden box so it amplifies the sound.
I could also have a 3.5 mm jack (input) so i can plug in my phone to use it as a normal amp.
I am not planning on having it working with only the on board speakers.
2 more outputs will be also used (one 3.5mm and one 6.4)
So to sum it up i want it to have
2 inputs 3.5 and 6.4
and 3 outputs speakers,3.5 and 6.4 (for use with an actual amplifier)

[madires]

This amp will be made for medium sized, and not so quiet room.
Ill be using it with my bass guitar and i am planning on using small to medium sized speakers with a wooden box so it amplifies the sound.

With 2" speakers you'll get a very lousy bass. If you got a proper datasheet for the speakers we could calculate the wooden cases volume required to improve bass, but I doubt it would help much. Better go for 8" speakers and design the amp for about 25W at least.

[FJV]

Hello i got 2  8 watt 14 ohm 2" speakers and i am wondering if i can increase the max volume (like overcklocking the speaker) with any kind of way ....
This may sound crazy but it may be possible i think.
Also could i use both speakers as one (by connecting them in parallel or in series ?)

Use the speaker as a driver for a horn speaker.

source :
http://en.wikipedia.org/wiki/Horn_loudspeaker

The main advantage of horn loudspeakers is they are more efficient; they can typically produce 10 times more sound power than a cone speaker from a given amplifier output. Therefore horns are widely used in public address systems, megaphones, and sound systems for large venues like theaters, auditoriums, and sports stadiums.

[madires]

Use the speaker as a driver for a horn speaker.

source :
http://en.wikipedia.org/wiki/Horn_loudspeaker

But not for a bass guitar :-) Horn speakers are used for midrange and high frequencies.

[ChrisGreece52]

This amp will be made for medium sized, and not so quiet room.
Ill be using it with my bass guitar and i am planning on using small to medium sized speakers with a wooden box so it amplifies the sound.

With 2" speakers you'll get a very lousy bass. If you got a proper datasheet for the speakers we could calculate the wooden cases volume required to improve bass, but I doubt it would help much. Better go for 8" speakers and design the amp for about 25W at least.

I dont want something loud because i will mostly use my pc speaker system (25watt RMS).

[ChrisGreece52]

Use the speaker as a driver for a horn speaker.

source :
http://en.wikipedia.org/wiki/Horn_loudspeaker

But not for a bass guitar :-) Horn speakers are used for midrange and high frequencies.

So i wont do it because i will use frequencies as low as 30 HZ.

[ChrisGreece52]

That transformer in the pictures is very small, it's 300mA maximum. You can't do shit with it when it comes to audio amplifiers.

Look for something in the range of 18v (either with center tap or two 9v secondary windings)  or a 24v transformer.

The transformer in the picture is a 500mah 9 volt one but i will need more info about connecting it in parallel so i can increase the voltage
Also sorry about the huge quote and sorry for my late response i just had time to read and answer.

[madires]

I dont want something loud because i will mostly use my pc speaker system (25watt RMS).

Which type do you got? Stereo squawk plastic boxes, 2 tiny speakers with a subwoofer cube or something more usable?

[madires]

So i wont do it because i will use frequencies as low as 30 HZ.

The 2" speakers will fall off around 100Hz very quickly, maybe even at a higher frequency.

[mariush]

The transformer in the picture is a 500mah 9 volt one but i will need more info about connecting it in parallel so i can increase the voltage

Dude...

You have voltage.

You have current.

Voltage multiplied by current gives you power.

That transformer is 9v  0.5 A  ... that's 4.5 watts.

No matter how many you put in parallel, the voltage remains 9v, just the current doubles, triples etc
No matter how many you put in series, the current remains 0.5A, just the voltage doubles, triples etc
9v is too low for a tda2050. No matter how much current you'd have by putting transformers in parallel, you still have just 9v.  If it starts at 9v, a tda2050 will only output about 1-2 audio watts, so the chip will only use about 3-5 watts (0.3-0.5 amps) out of how many amps your transformers in parallel would be able to provide.

If you put 9v transformers in series, you may have 18v, 27v, 36v ac or dc but your current will still be 0.5a
Let's say you put  3 in series to get 27v 0.5a. That's 13.5 watts. I don't know if it's 9v ac rms or 9v DC coming out of that. Let's just say 27v DC. 
If you go in datasheet at the graph, you look at +/- 13v (because the graph is for split power supply) and you see the amplifier chip has the potential to output up to about 7 watts. At about 60-70% efficiency, that means that to output a single channel (one amplifier), to output about 7 watts of audio, the chip will use about 10 watts.
Your 27v 0.5a will be enough, for ONE channel. 
If you put two amplifiers, one for each channel in stereo, they'll both use about 10 watts, 20 watts in total... but your power supply can only provide 13.5 watts.  Your power supply is undersized, even with 3 transformers of that type in series.

Do you understand the concept that the amplifier can not output audio watts if there's not enough power at the input? If you give it 10 watts from the mains, how do you expect to get 20 audio watts?

Use that 9v transformer for other stuff, it's not suitable for audio amplifiers.
Like I said, you need something like 24v AC rms 40-60 VA  (about 1.5A) to get about 20-25w of sound.

[ChrisGreece52]

I dont want something loud because i will mostly use my pc speaker system (25watt RMS).

Which type do you got? Stereo squawk plastic boxes, 2 tiny speakers with a subwoofer cube or something more usable?

Something more usable its pretty old but still going strong
Its a Logitech X-420 2.1 system.
2 satelites and one subwoofer
http://www.newegg.com/Product/Product.aspx?Item=N82E16836121010
I got it for about 7 years .... ( i did not know that it has been so long ... )
good quality wooden woofer and i think it is the best i had (and the first i had )

[ChrisGreece52]

So i wont do it because i will use frequencies as low as 30 HZ.

The 2" speakers will fall off around 100Hz very quickly, maybe even at a higher frequency.

well that sucks.......

[ChrisGreece52]

The transformer in the picture is a 500mah 9 volt one but i will need more info about connecting it in parallel so i can increase the voltage

Dude...

You have voltage.

You have current.

Voltage multiplied by current gives you power.

That transformer is 9v  0.5 A  ... that's 4.5 watts.

No matter how many you put in parallel, the voltage remains 9v, just the current doubles, triples etc
No matter how many you put in series, the current remains 0.5A, just the voltage doubles, triples etc
9v is too low for a tda2050. No matter how much current you'd have by putting transformers in parallel, you still have just 9v.  If it starts at 9v, a tda2050 will only output about 1-2 audio watts, so the chip will only use about 3-5 watts (0.3-0.5 amps) out of how many amps your transformers in parallel would be able to provide.

If you put 9v transformers in series, you may have 18v, 27v, 36v ac or dc but your current will still be 0.5a
Let's say you put  3 in series to get 27v 0.5a. That's 13.5 watts. I don't know if it's 9v ac rms or 9v DC coming out of that. Let's just say 27v DC. 
If you go in datasheet at the graph, you look at +/- 13v (because the graph is for split power supply) and you see the amplifier chip has the potential to output up to about 7 watts. At about 60-70% efficiency, that means that to output a single channel (one amplifier), to output about 7 watts of audio, the chip will use about 10 watts.
Your 27v 0.5a will be enough, for ONE channel. 
If you put two amplifiers, one for each channel in stereo, they'll both use about 10 watts, 20 watts in total... but your power supply can only provide 13.5 watts.  Your power supply is undersized, even with 3 transformers of that type in series.

Do you understand the concept that the amplifier can not output audio watts if there's not enough power at the input? If you give it 10 watts from the mains, how do you expect to get 20 audio watts?

Use that 9v transformer for other stuff, it's not suitable for audio amplifiers.
Like I said, you need something like 24v AC rms 40-60 VA  (about 1.5A) to get about 20-25w of sound.

Well you will be happy for this !!!! i GOT IT finally i was confused (very confused) but now i got everything but in your reply sou said something that is well suited for me.
you said that if i connect 3 windings in series i will get 13.5 watts for power ... thats more than enough for one channel use
2 channels is optional as i said.

[mariush]

nevermind. I read incorrectly and thought you meant parallel.

Anyway, it's just stupid to use three transformers, unless you already have them.

Just go buy a 24v ac transformer rated for about 20 watts at least, they should be cheap. Or.. I don't know, maybe find two car/motorbike batteries and put them in series to get 24v.

[madires]

Something more usable its pretty old but still going strong
Its a Logitech X-420 2.1 system.
2 satelites and one subwoofer
http://www.newegg.com/Product/Product.aspx?Item=N82E16836121010
I got it for about 7 years .... ( i did not know that it has been so long ... )
good quality wooden woofer and i think it is the best i had (and the first i had )

I see. IIRC the satellites got a second passive speaker to boost lower frequencies. Those are ok for FPSs but lack a proper frequency response for higher frequencies. Midrange is "thin" and high frequencies are poor. But some people like that kind of sound. Just don't try to play classic music :-)

[madires]

The 2" speakers will fall off around 100Hz very quickly, maybe even at a higher frequency.

well that sucks.......

That's why I recommend a 8" speaker. If you add a bass booster to your amp you'll get away with a smaller speaker (6"), but I woudn't go any smaller. Driving such a speaker with 10W should sufficient for a quiet midsized room. With a noisy background (talking people) you have to crank up things considerably.

[ChrisGreece52]

nevermind. I read incorrectly and thought you meant parallel.

Thats ok

Anyway, it's just stupid to use three transformers, unless you already have them.

No i do not have them but i thougth i could put 3 Windings in series (not transformers)

And

Just go buy a 24v ac transformer rated for about 20 watts at least, they should be cheap. Or.. I don't know, maybe find two car/motorbike batteries and put them in series to get 24v

24v AC you mean just a regular 220 Volt 50/60 hz to 24 DC right???
Also from another topic a member suggested that i whould look for the power the transformer can deliver so if i want a dual signal amp i am going to need at least 20 watts
Right

[ChrisGreece52]

The 2" speakers will fall off around 100Hz very quickly, maybe even at a higher frequency.

well that sucks.......

That's why I recommend a 8" speaker. If you add a bass booster to your amp you'll get away with a smaller speaker (6"), but I woudn't go any smaller. Driving such a speaker with 10W should sufficient for a quiet midsized room. With a noisy background (talking people) you have to crank up things considerably.

What would you suggest with a medium sized room with medium silence level
8" with 15 watts will be good ?

[madires]

What would you suggest with a medium sized room with medium silence level
8" with 15 watts will be good ?

Could work, but it's better to have some reserves, like 30W. The TDA2050 delivers 32W but at high power levels the distortion increases. Give it a try :-) If the TDA2050 doesn't provide enough power you could upgrade later on. 

[ChrisGreece52]

What would you suggest with a medium sized room with medium silence level
8" with 15 watts will be good ?

Could work, but it's better to have some reserves, like 30W. The TDA2050 delivers 32W but at high power levels the distortion increases. Give it a try :-) If the TDA2050 doesn't provide enough power you could upgrade later on.

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 !!!

[ChrisGreece52]

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 ?

[madires]

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 !!!

12v with 2.5A will give you about 25W DC. Now we have to consider the efficiency of the amp (around 2/3) and end up with 16W audio. If you keep things modular, you can start with that transformer and a TDA2050 module. If you need more power later on upgrade to a higher rated transformer. The old one will be useful for another project :-)