Have questions about TDA2050 Amp Circuit.

Long story short. Started teaching myself electronics 4 months ago. My first circuit was an LM386 mini amp. Had lots of questions but slowly answered them by trial and error. Moved on with simple FM transmitter and got it to work fairly. Eventually decided to build a TDA2050 amp. I googled for answers but found nothing useful. Now I hope the awesome people on this forum can help. Thanks in advance.

Question #1: How do you measure Output Watts of an Amp Circuit? I tried just hooking up my Meter to my 12V DC power supply and when I cranked it as hard as I could go without distortion, it would only draw 0.35A. That only equals ~4W but the datasheet claims 35W RMS into 4ohms with 18V-22V Power Supply. I grabbed my Laptop's 19V Supply and only got about max 0.4A. Thats still only ~8W. Anyone know what I'm doing wrong? Also the datasheet claims Max of 5A current output and I'm no where near that.

Question #2: I used the Single Supply Circuit on the datasheet instead of the Split Power Supply Circuit because I didn't know what they meant by +Vs and -Vs. Does +Vs mean positive battery terminal and -Vs is negative battery terminal? It can't be that easy can it?

Question #3: Will the Split Power Supply Circuit sound better than the Single Supply Circuit? Any difference?

Question #4: The circuit didn't specify the voltages of capacitors or the wattage of resistors. Does it matter what Caps I use and what watt rating I use for resistors?

Again I would appreciate all help and I will always help anyone else in need when I learn more about this awesome world of electronics.

Trance183 said:

Question #1: How do you measure Output Watts of an Amp Circuit? I tried just hooking up my Meter to my 12V DC power supply and when I cranked it as hard as I could go without distortion, it would only draw 0.35A. That only equals ~4W but the datasheet claims 35W RMS into 4ohms with 18V-22V Power Supply. I grabbed my Laptop's 19V Supply and only got about max 0.4A. Thats still only ~8W. Anyone know what I'm doing wrong? Also the datasheet claims Max of 5A current output and I'm no where near that.

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Maximum power from a single-ended amplifier from 12V is only 4W in to a 4 ohm load, and a TDA2050 won't approach that off 12V..

The datasheet certainly won't claim 35W with only an 18V supply. A quick look shows that they specify 18W in to 8 ohms from a 44V supply, and 28W in to 4 ohms from the same 44V.

I think you got wrong datasheet.

Thanks for the quick reply. The datasheet I have for the TDA2050 has a maximum rating of +-25V. And I was using 19V so I should at least get over 15W right.

1) The maximum output for an ideal amp with a 19V single supply is 19Vpp. Thus the rms voltage is 19/2*.707 = 6.7V. The power into a 4Ω load would be 6.7²/4 = 11W. In practice the amp has some voltage drop so the likely maximum power would be under 10W.

2) No it's not that easy. A split supply means two supplies. The positive supply has negative connected to ground and, and the negative supply has positive connected to ground.

3) There should be no difference in sound between a single and split supply for the same voltage across the amp (single supply voltage equals the sum of the two split supply voltages).

4) In general, the cap voltages should be at greater than the supply voltages. The resistor power is V²/R where V is the voltage across the resistor. Use a resistor power rating that's a least double that value.

Trance183 said:

Thanks for the quick reply. The datasheet I have for the TDA2050 has a maximum rating of +-25V. And I was using 19V so I should at least get over 15W right.

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Not unless you're using +/-19V (38V) - a single ended ampliifer off a single 19V supply will be pretty low. (6W or so?)

Thank you so much crutschow. So to get the most power out of this amp I must use Split Supply? If the max rating is +-25V does that mean I can use up to 50V DC Single Supply?

Thank you very much Nigel. So that explains why my amp cannot push my 6" Car Side Door Speaker. It sounds so low. And when I crank it higher it distorts very easily.

Trance183 said:

Thank you so much crutschow. So to get the most power out of this amp I must use Split Supply? If the max rating is +-25V does that mean I can use up to 50V DC Single Supply?

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You should be able to use a single supply of 50V, which would give the same power as a 25V split supply.

To get more power from a car supply, you could use an amp with a bridge output such as the **broken link removed**. That will double the voltage across the load, giving about 15W into a 4Ω load with a 14.4V supply (engine running and charging). You can go as low as a 2Ω speaker (or two 4Ω in parallel) which would double the power to about 30W. To use this device the speakers must be floating (none of the terminals to ground).

A TDA2050 is a single amplifier that is used with a high voltage supply. Car amplifier ICs like the TDA2005 or TDA7240A have two amplifiers (called a bridged amplifier) and drive each wire of a speaker with nearly double the voltage swing of a single amplifier which also nearly doubles the current and produces nearly 4 times the power. Bridged amps do not need the huge output coupling capacitor that causes a huge POP in the speaker when a single ended amplifier is turned on or off.

Don't guess at the numbers, look at the graphs on the datasheet.
The TDA2050 has an output of 4.5W into 8 ohms with a 19V supply or maybe (at the very bottom of the graph) only 2.5W into a 4 ohm speaker with a 13V supply.
A TDA2005 or TDA7240A produces 13W into 4 ohms with a 13V supply.
My car has some 2 ohm speakers for nearly 25W each with a 13V supply.

When you turn up the volume higher than the max voltage swing possible with your supply voltage then the amp clips the signal and it is distorted.

Wow! I will order one of those ASAP. But as for the floating, if the negative speaker terminal doesn't go to ground then where does it go? lol sorry I am still new to this.

Oh my gosh! Audioguru you are awesome man. Thanks alot buddy. I feel like a total noob. But yes that all makes sense. I am sadly using the wrong chip for what I want to do. This forum is the best. If you guys have any more simple troubleshooting tips for us noobs, I know I will run into them very soon.

Trance183 said:

Wow! I will order one of those ASAP. But as for the floating, if the negative speaker terminal doesn't go to ground then where does it go? lol sorry I am still new to this.

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If you look at the data sheet you will see that the amp has two outputs for the speaker. These go directly to the speaker terminals and must not be grounded.

You can learn a lot from a data sheet.

The bridged amplifier has an output for each wire of a speaker so the voltage swing is nearly doubled which causes the current to be nearly doubled which causes the power into a speaker to be nearly 4 times as much as a single amplifier.

I agree. But I pulled up the Datasheet of the chip you recommended and saw that they grounded Pin 5 and Pin 7 so that confused me again. But I guess thats not called grounding when you put a resistor and cap towards ground. I still have alot to learn and I really appreciate you guys taking time to help me here. I'm sure this thread will come in handy with other noobs like me.

So to power my car speakers what do you recommend? TDA7256 or TDA7240 or TDA2005? Of course I will buy one chip for each speaker. But I want the most power and best sound for the price.

I have decided to go with the TDA2005 since it is the easiest to get a hold of. The rest are double the price as well. Thank you.

So let us know how the TDA2005 works for you.

The TDA2005 and the TDA7240A both do not have pin 5 and pin 7 grounded. They both have the same spec's.
The TDA7256 can drive a 2 ohm load with more power but is the same as the other two when it has an 8 ohm or 4 ohm load.

You never told us the impedance of your speakers. It determines the max output power.

Thanks audioguru, sorry for late reply, my internet went down for a whole day, but yes my speakers are 4ohm 6inch side door speakers. So I think the TDA2005 will do just fine. I also have a 6ohm Cheap Subwoofer. Just don't know how to apply that to my circuit. lol.

Oh wow! I found a chip called TDA7377 and according to this chip its stereo 2x30W Dual/Quad amp. I will order this one too. I shall return to see how the chips work out.