How much power do I need?

[audioguru]

The Amp6-Basic is class-T, not class-D, and each channel is bridged. It has almost the same amount of output power as any other stereo bridged car radio amp IC.

With a 13.5V supply its power at clipping into 8 ohms is 7W and into 4 ohms is lower than most at only 11W.
With a 12V supply its power at clipping into 8 ohms is about 5W and into 4 ohms is about 8W.

It operates a little cooler than a class-AB amplifier IC.

 

[Mr RB]

The Amp6-Basic is class-T, not class-D, and each channel is bridged. It has almost the same amount of output power as any other stereo bridged car radio amp IC.

With a 13.5V supply its power at clipping into 8 ohms is 7W and into 4 ohms is lower than most at only 11W.
With a 12V supply its power at clipping into 8 ohms is about 5W and into 4 ohms is about 8W.

It operates a little cooler than a class-AB amplifier IC.

Yeah I saw you make the same mistakes in your calc the first time you posted. I'm guessing you're using calcs for a linear amp as I know you're not stupid. You probably don't work with switchmode stuff much.

From the TA2020 datasheet;
Vin= 13.5v, continuous average output power 18w into 4 ohms
Vin = 14.6v, cont average output power 25w into 4 ohms.

And for the record I said "class D" as I'm not sure "class T" is anything more official than a Tripath marketing term for their own amp chips which are a proprietary variation of class D.

If you can show that "class T " is an officially recognised amp topology then I stand corrected on that.

As for "operates a little cooler"... Again from the datasheet;
efficiency 88% at output 12w into 8 ohms...
That's one heck of a LOT cooler than a 20w capable linear amp running 12w into 8 ohms!

 

[Nigel Goodwin]

Yeah I saw you make the same mistakes in your calc the first time you posted. I'm guessing you're using calcs for a linear amp as I know you're not stupid. You probably don't work with switchmode stuff much.

Been switch-mode makes no real difference, although it 'may' gain a little bit from the possible lower voltage losses. Assuming no losses whatsoever in the amplifier, a 13.5V supply, feeding a bridged amplifier, could provide 22W.

Personally, I'd rate such a bridged car type amplifier at only 16W in to 4 ohms, or single-ended 4W into 4 ohms. For 8 ohms, half those power outputs.

 

[audioguru]

With a 13.5V supply, the Tripath TA2020 produces only 11 Watts into 4 ohms at clipping, or 18 Whats with it clipping its head off with a severely distorted square-wave output.
Never mind how much is its distorted output with a 14.6V supply since your supply is only 12V where it has a very low output power.

Don't you know that a power amplifier can produce up to twice as much output power when its output is a square-wave? Half the power is in the harmonics.

When an amplifier is clipping then it is more efficient. The TA2020 is only 79% efficient when its power is 7W at clipping into 8 ohms with a 13.5V supply. Its efficiency is not shown when its supply is as low as 12V.
A TDA7240A bridged linear amplifier is 67% efficient at clipping which is not much different than the 79% efficiency of the Trident TA2020.

In your case with a 12V supply the output power into 8 ohms is low and the amount of wasted power is also low.

The TA2020 produces 12 Whats into 8 ohms with a 14.6V supply when it is clipping its head off with a severly distorted square-wave output.

Look at the graph in the datasheet.

 

[tcmtech]

As I reread the thread I see the fact that its a boom box with battery power at around 12 volts at best. Most portable sound systems with battery power have 8 ohm speakers and what point is there if 4 ohm speakers are being used.

Batteries get used up fast enough any way so there is no point trying to get more watts out to the speakers. Plus I doubt it gets ran at full volume for very long so the peak power of the amplifier and what distortion level at what wattage it can produce at at that level is pointless.
For a battery powered device at 12 volts, 5 watts with 1% distortion is a reasonable number I think. If you want more power you should get lower ohm speakers and a amplifier IC that can handle it.

I have seen some manufacturers of car audio making 1 ohm speakers for factory systems now so they can run a fair amount of wattage without going to voltage boosting power supply's in the car amplifiers.

I have a new Pioneer CD deck that has a 45 watt per channel at 2 ohm rating!
Nit pick it all you want but its still rated at 28 watts per channel at 12 volt input with 2 ohm speakers at 1% THD and 40 watts per channel at 14.4 volt input with 2 ohm speakers at 1% THD.

 

[audioguru]

The 6X9 speakers on the rear shelf of my car are 2 ohms. They can play very loudly.
The front speakers are probably 4 ohms with 20W each.
The sub-woofer is 10" and it has an amplifier with about 120W RMS.

 

[Mr RB]

With a 13.5V supply, the Tripath TA2020 produces only 11 Watts into 4 ohms at clipping, or 18 Whats with it clipping its head off with a severely distorted square-wave output.
Never mind how much is its distorted output with a 14.6V supply since your supply is only 12V where it has a very low output power.
(snip)

My apologies audioguru, I saw the photo that had some sizable inductors on the PCB and quickly glanced at the datasheet and saw the continuous average power figures, and assumed the amp operated in some type of smps boost mode.

I've worked on 12v car audio amps (can't remember the chip name) but the amp chip had integral boost converter built in to it to give higher power from the low voltage supply. Without even looking properly at the datasheet or its schematic I assumed the TA2020 was a similar deal and started shooting my mouth off.

 

[audioguru]

Philips make the TDA1562 class-H mono car amplifier IC. It has a powerful supply voltage doubler and uses two amplifiers in a bridge.
It turns on the voltage doubler only when needed to reduce its heating.
With a 14.4V supply its output at clipping into 4 ohms is 55 Watts.

Of course its power into 8 ohms is slightly more than half and with a 12V supply its power into 4 ohms is about 35W and into 8 ohms is about 20W.