Can I use a 2A transformer to power 4 TDA2050 amplifier chips?

[Averagesupernova]

You are really confusing things here by referring to channels and to stability under load.

I can't possibly see how. Point it out and we'll clear it up.

But it requires not one, but two amplifiers, (plus a phase splitter), which is “half as cheaper”, so the advantage is cancelled.

A lot of commercially available car audio amps are 2 channel amps for stereo mode with for instance 50 watts per channel at 4 ohms. Suppose a person wants to run an 8 ohmsubwoofer. A 2 channel amp that is not bridgeable cannot run a single 8 ohm coil subwoofer at 100 watts where a bridgeable amp can. To do this would require a dual voice coil subwoofer with 4 ohm coils. So the manufacturers build multi-channel amps that are bridgeable to cover the applications where people want to just run stereo mode to run speakers in the kick panels or doors, or in bridge mode to run a single subwoofer. My '65 Ford has a 4 channel amp for front and rear speakers and a 2 channel running bridged to run a sub. As far as I know, single channel amps in car audio are geared towards running only subwoofers and are class D and are considerably more than a measly 50 watts. So don't bring it up. For that matter, my home theatre powered sub is class D also. It's not limited to car audio.

 

[jim hardy]

The TDA 2050 datasheet says in table 2 that output peak current is internally limited to 5 amps.
Again, the datasheet at ST's site is more legible than that third party copy ( I have a real resentment against those for-profit third party sites barging into search engines and cluttering things with their ads - what good are they doing anybody? I avoid them like the plague.)...

So I think I agree with others, one should ask 'what's the advantage of bridging? '

Most of you guys know the sound terms in next paragraph but i'll try to explain each as it's introduced anyway.

Bridging would let you push 5 amps through 8 ohms instead of 4 ohms..
That should double power output.
But the ear is logarithmic and that's why we have decibels(db) to measure sound power level(spl).
"spl" is usually usually expressed in 'db', which refers to some number of pascals of sound pressure;
db = 10 X log(Pmeasured/Preference)
and doubling the power adds only 3 db of spl,,,, which most listeners would not notice.

Would somebody who's still young and sharp please check my arithmetic here ? I'm reaching back to 1963 for this...

If we take a speaker that's rated 90db spl at 1 watt and drive it with 50 watts
we'd add about 10log(50/1) = 17db to its 90db of spl
and get 90+17=107 db of sound (quite a lot).

Bridging the amplifiers and buying an 8 ohm speaker instead, and driving it to 100 watts
would similarly add 10log(100/1) = 20db
and give us 90+20=110db

Now that's twice as much power, but twice is barely enough for the average ear to notice.
It'll sound like it got louder by the ratio of 110/107 = 1.028, not quite 3%.
All that work for 3%? Bah, humbug!

That's why I tell people "If fifty watts isn't enough for you then you need five hundred."
And that's because of the human ear's logarithmic characteristics. You have to admit - 107 vs 110 isn't worth a lot of effort unless you're into those car stero competitions where they actually measure sound pressure level with expensive instruments.

But to tesladude's question -
a ten amp supply for your +24 and another for your -24 will deliver all the current that a stereo pair of TDA2050 based amplifiers should allow to pass, regardless whether the individual amps are single TDA's (2 total) or bridged TDA's (4 total).

If you bridge you should go to 8 ohm speakers.

old jim

 

[Averagesupernova]

Now Jim, 3 db can mean the difference between hearing the music and feeling it. :)
-
Some amps are 2 ohm stable, and with good reason. A lot of car audio speakers are 4 ohm. Take a 4 ohm speaker (or run two 8 ohms speakers in parallel) and run bridged and you have 4 times the power as compared to running it from a single channel. Each channel sees 2 ohms.

 

[jim hardy]

So long as your amp is not current limited...
If it IS current limited then to maximize power you want to push that amount of current through as many ohms as you can.

.....

:) :):) Ahh that feel - track 12 of the Titanic soundtrack CD... :) :) :)
I was so proud of my Electrovoice 12's...

here's some speakers my kids built - array of cheap woofers..

They compared well with the Altecs in background...

 

[Tesladude]

Ok so would running bridged tda2050 on an 8 ohm speaker give me a noticeable increase in volume?When I first started all this I was going to use a simple linear power supply to run 2 tda2050s giving me left and right ear at a reasonable volume on an 8 ohm speaker. I tried it, and It didn't seem loud enough for me.
I wanted to continue useing the tda2050 because of it's simplicity, low voltage, and price.
So, having little experience with bridge, I figured I would just have 2 bridge circuits to give me a lot more power for each ear. I read if you have 100 watts into 4 ohms, then bridge you will have 200 into 8.
If that is so then bridged I will have 60 watts into 8ohms since this chip does 30 watts into 4ohms.
Then came in a suitable power supply for this and unless the bridged plans are changed, then that's where I am with this.

Now from what I think I am hearing up above is that this will not give me more volume?(virtually) And it is not worth the effort?

 

[Tesladude]

That I would show what I am working with here.

 

[meBigGuy]

You are doing single ended drive, so all my peak currents were 2:1 high.

1. Your transformer says 6 0 6, which you are rectifying and filtering. Measure the voltage across the amplifier please (no audio) , and post it. (could be around 6.8V if you are using a full wave rectifier. More if you are using a bridge.

2. Put your speaker in an enclosure. Even a cardboard box will make a significant difference. Speakers sort of "cancel themselves out" if there is no front to back isolation.

3. 7 volt pp Sine wave RMS voltage is 3.5*0.707 = 2.47 volts which gives 1.5 watts average power into 4 ohms for a sine wave

4. Peak current is 3.5/4 = 0.875 amps. Music is maybe 5 to 1 peak to average ratio, which would give you 175ma on your meter. Your supply probably has all sorts of ripple. It probably drops to 5 volts or less on loud peaks. MEASURE THE SUPPLY VOLTAGE WHILE PLAYING LOUD MUSIC

5. PLEASE DRIVE A SINE WAVE AND MEASURE THE SPEAKER VOLTAGE AND CURRENT AND THE POWER SUPPLY VOLTAGE.

6. with 24V single ended you will get +-3 amp peaks, 3*.707 = 2.1 amps rms from a sine wave. Sine wave Power is 8.4V RMS into 4 ohms which is 18W.

7. with 48V single ended you get +-6A peaks = 4.2A RMS from a sine wave. This gives 16.9V RMS which into 4 ohms is 71 watts for a sine wave. (same as 24 volt bridge)

 

[jim hardy]

Ok so would running bridged tda2050 on an 8 ohm speaker give me a noticeable increase in volume?

It would give you a barely noticeable increase in perceived volume, because the ear is non-linear. Mother Nature made it that way so we can hear little things stirring in the night as well as very loud big things nearby.

When I first started all this I was going to use a simple linear power supply to run 2 tda2050s giving me left and right ear at a reasonable volume on an 8 ohm speaker. I tried it, and It didn't seem loud enough for me.

If that picture is your setup then you are starving your TDA for power.
You probably have around 8 volts going to it which drops fast as it tries to make any honest amount of power. You can't run a Corvette V8 engine with a Briggs&Strattom lawnmower carburetor.
You need a stout source .
That transformer is preposterous - you need one that weighs at least three pounds.
e.g. http://www.mouser.com/ProductDetail/Hammond/182N18/?qs=%2fha2pyFadujvAPpAo%2fzTEzr5eMEjvsXv%252beHkdMeGhUg%3d

Also speakers in free air sound terrible because the air behind the cone simply shuffles around to the front allowing the cone to travel to its limit with quite modest power . That's contributing to your perceived distortion. Cut a hole in a piece of cardboard for the speaker (a primitive baffle) and place it atop a wastebasket(primitive enclosure) . You'll hear a difference as you move it toward the enclosure.

I wanted to continue useing the tda2050 because of it's simplicity, low voltage, and price.
So, having little experience with bridge, I figured I would just have 2 bridge circuits to give me a lot more power for each ear. I read if you have 100 watts into 4 ohms, then bridge you will have 200 into 8.
If that is so then bridged I will have 60 watts into 8ohms since this chip does 30 watts into 4ohms.
Then came in a suitable power supply for this and unless the bridged plans are changed, then that's where I am with this.

Where you are is you have mis-diagnosed your problem.
What you think is insufficient amplifier is actually insufficient power supply for the amplifier that you have.

Now from what I think I am hearing up above is that this will not give me more volume?(virtually) And it is not worth the effort?

Well- give the single TDA a chance by hooking it to an adequate power source. Then you'll be in a better position to judge its need for improvement.

Can you borrow two 12 volt batteries? Lawnmower or motorcycle batteries would be perfect, easier to carry than car batteries. Even at +- 12 volts that TDA will make ten watts which will blast you out of the room before it distorts.
And baffle that speaker. The whole premise of loudspeaker design is to separate the front from the rear of the cone.

After you've tried the TDA with adequate power supply and baffled the speaker let us know how it sounds.

I predict you'll be quite happy with the single TDA configuration. Bridging will make it sound only a teeny bit louder.

Your heatsink is way too small for the final design. Pillage a big one from a junked car stereo.

old jim

 

[Tesladude]

Ya don't worry bout the heat sink i got one in mind for later.
The 6-0-6 actually puts out 18v after bridged, which is the typical supply, last time I listened to it on an actual LARGE speaker cabinet I may have accidentally been powering it with 12 volts which I had used on another circuit the day before, I just hooked it up useing this transformer with a large speaker cabinet and, now, I think it does sond good, I then put another transformer I had that was rated 3 amps at 12-0-12, I regulated it to 24 and you know what, I liked it.

Everybody forget the bridging !

OK so now that I only have the 2 tda2050, using a switching power supply will make it so I have to set them up for a non-splut power supply, because I won't have the ground, will this lower the loudness at all?

 

[jim hardy]

OK so now that I only have the 2 tda2050, using a switching power supply will make it so I have to set them up for a non-splut power supply, because I won't have the ground, will this lower the loudness at all?

12-0-12 split supply allows ~24 volts peak to peak across your speaker.

If you use a single 24 volt switcher you can get the same peak to peak by using the single supply schematic figure 6 in datasheet.

If you use a single 12 volt switcher, yes you will limit your power because you can only get ~12 peak to peak volts.Note the differences between split(dual?) and single supply schematics, fig 4 and fig 6.
Observe that single ended requires a huge capacitor to block DC from the speaker,
that 1000 uf shown rolls off your low frequency at ~40 hz. That helps protect the speaker if it's in a vented enclosure, but some enthusiasts prefer to not have that capacitor..
And the single has a biasing network on front end to set output mid supply.If you use two switchers in series, that is connect one's + to the other's - , you can use that junction you just made of + to - as the "ground" ( I prefer to call it circuit common) and stick with your split supply schematic. I'd use two of them set for about 22 volts.

If you use a single supply, you can go to almost 50 volts. I'd probably use a 48 volt supply tweaked down to 44.

Well, actually i'd buy a centertapped toroid and make a linear split supply...

Whatever you do, pay attention to their "suggestions" on pages 5 and 7.

Enjoy this, it's a fun hobby. I hope you get into speaker building, Thiele parameters and all that.

old jim

 

[Tesladude]

So sonnet the switching supplies in seriece and use the posotive and negativ connection in the center as ground for a split supply?
What can the max current on these be to run 2 of these chips?

 

[jim hardy]

So sonnet the switching supplies in seriece and use the posotive and negativ connection in the center as ground for a split supply?

yep.

What can the max current on these be to run 2 of these chips?

Ten amp supplies should do nicely , that'll leave a little room to spare for some lights and preamps... if you're pinched for funds six amp supplies would do for most listening.

 

[Averagesupernova]

Something here that is worth mentioning concerning doubling power making only a small perceived increase in volume. Just about all speakers from years ago were 8 ohms. 4 ohm speakers came along for automobiles because stock car radios have a limited supply voltage of 12 volts and you won't get much more than 10 volts peak to peak which is about 1.5 watts into 8 ohms. So the solution to get more power out of a low voltage power supply was to drive a lower impedance speaker. Someone thought that it was worth building 4 ohm speakers instead of 8 to get the small perceived difference in loudness.

 

[Tesladude]

Something here that is worth mentioning concerning doubling power making only a small perceived increase in volume. Just about all speakers from years ago were 8 ohms. 4 ohm speakers came along for automobiles because stock car radios have a limited supply voltage of 12 volts and you won't get much more than 10 volts peak to peak which is about 1.5 watts into 8 ohms. So the solution to get more power out of a low voltage power supply was to drive a lower impedance speaker. Someone thought that it was worth building 4 ohm speakers instead of 8 to get the small perceived difference in loudness.

Thanks, I was actually wondering a little bout that so it helps.

OK so I hate to drag this out even further but if I wanted to have 2 outputs for left and right ear, giving total of 4, would it be ok to just put 2 8Ω cabinets or speakers in parallel, or would it be worth having 4 amplifiers to run each output.

 

[Averagesupernova]

If an amplifier is capable of driving the combined impedance it would not hurt to run them in parallel. In the case of my '65 Ford I did not do this since I wanted to be able to tweak each speakers level and frequency response curve independently.

 

[Tesladude]

Ok thanks, I was looking at prices for power supply and I think I want to try and use single supply circuit with one 10a 24v smps.

This will save me room and money.

http://www.google.com/imgres?imgurl...OJAFUsbkCYHW2AWV5YDwAw&ved=0CD0Q9QEwBA&dur=97As you said before the 1000uf will cut out everything bellow 40hz, I still want some of that though.
Will changing to 2200 or somthing else cut out a bit less?

 

[jim hardy]

Ok thanks, I was looking at prices for power supply and I think I want to try and use single supply circuit with one 10a 24v smps.

This will save me room and money.

http://www.google.com/imgres?imgurl...OJAFUsbkCYHW2AWV5YDwAw&ved=0CD0Q9QEwBA&dur=97


As you said before the 1000uf will cut out everything bellow 40hz, I still want some of that though.
Will changing to 2200 or somthing else cut out a bit less?

read the datasheet - it gives you precautions about that capacitor on page 7 of 16, the note in ' single supply applications suggestions'. You might need a 40 volt supply if you make it bigger than 1000 uf.

 

[meBigGuy]

You might need a 40 volt supply if you make it bigger than 1000 uf.

C7 can be larger than 1000 μF only if the supply voltage does not
exceed 40 V

Bigger capacitor is no problem below 40 volts.

If I were doing this I would buy a +-12V supply (or higher) and eliminate the output capacitor.

Large electrolytics can be non-linear, and it always cuts the base response.

Going to higher voltage gives you more dynamic headroom, which makes for a cleaner sounding transients (drums, etc). It's not just about perceived loudness.

 

[jim hardy]

Bigger capacitor is no problem below 40 volts.

Right, that's what the note on datasheet says, I had that backward for some reason... This " gettin' old " ain't for sissies I tell ya...
Now everybody has seen those precautions.

If I were doing this I would buy a +-12V supply (or higher) and eliminate the output capacitor.

not to mention he's already built one circuit board for split supply amplifier .

 

[Baluncore]

Capacitor or no capacitor? There are three topologies.

1. Use a speaker coupling capacitor and a single supply. Optimise low frequency response by using a high impedance speaker.

2. Use a split supply. Then speaker coupling capacitors are not needed and response is to DC. The split supply requires two storage capacitors, but they only have to filter down to twice the lowest mains frequency = 100Hz. Split SMPS are rare so you might have to buy two.

3. Use a phase splitter to drive two separate amplifier chips in bridge mode, both on the same single power supply. A SMPS is the obvious solution. Do you remember that link? $16.95 for a 54V, 5.2A SMPS;
http://www.allelectronics.com/make-a-store/item/PS-545/54VDC-5.2A-SWITCHING-POWER-SUPPLY/1.html

 

[Tesladude]

I will need to supply other things on this project so I think I will need more current but That is a great deal and I will totally keep it in mind.

So you guys were sayin just take out the 1000uf? wouldn't that cause dc related problems?

 

[Baluncore]

If you remove the capacitor then you must go to topology 2, (a split supply), or topology 3, (a bridged pair of chips with a single supply).

 

[meBigGuy]

Personal Opinion here. I think an output capacitor in series with a speaker is a huge degradation of the system performance due to capacitor non-linearities and loss of low frequencies. I like the split supply for its amplifier simplicity, but the bridged amplifier makes sense if a split supply is not practical (ie not cheap nor available).

The currents required are deterministic. The peak current is maximum voltage across speaker divided by speaker impedance. The supply should be able to deliver that peak current to both channels for at least 100ms without limiting or drooping. Most commercial supplies will supply well in excess of their rated current for short durations, just as long as you don't exceed the power dissipation rating.

Do a google search on Amplifier Power Ratings. There are many good explanations and examples.

 

[Tesladude]

Ok thanks guys I think i have everything I need. But just a couple random questions if you don't mind,

On some pre made audio modules or kits I have found that the 1,2.2, or 3.3uf capacitor in seriece with the input are being used with a few 100v capacitors and vet everything else is normal, it is just the input so why would they do that?

In a split supply, and other supplies, you have the decoupling capacitors to stop any supply, but many circuits have like a .1uf cap in parallel with a 220uf decouple cap, what is special about 220.1uf?

Also can I combine a left and right audio output and put them both into the posotive of one speaker to get a speaker that is putting out left and right (center speaker) without doing any harm to the amp or anything?

 

[Baluncore]

They isolate the DC level between modules and so separate the pre-amplifier's front end DC bias from any unknown DC input . With high impedance amplifiers, AC input coupling capacitors can be small.

220uF is a big slow electrolytic capacitor with significant self inductance. 0.1uF is a fast ceramic capacitor. They each handle a different part of the frequency spectrum.

No, you cannot combine low impedance outputs directly. To sum two channels into a single speaker you would need to drive each side of the speaker with a different amplifier, that would require you invert the input to one amplifier only so as to reverse the speaker difference phase.

 

[sophiecentaur]

To put L and R channels into one speaker you need to combine at low power and then amplify. Two low impedance (high power) outputs in parallel will involve impossible levels of difference currents as they 'fight' each other.

 

[jim hardy]

Also can I combine a left and right audio output and put them both into the posotive of one speaker to get a speaker that is putting out left and right (center speaker) without doing any harm to the amp or anything?

There do exist dual voice coil drivers , usually big ones for low frequencies. You could use one of those with one of its coils driven by each amplifier
but little speakers are so cheap why not just put two in one box?

 

[Tesladude]

Ok! Thanks guys!