Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

How to power up two stereo audio amplifiers from a single source of power supply

learning

Member
Could you tell me how to power up two stereo audio amplifiers from a single source of power supply?

Configuration:


4 x Woofers (4 ohm/20 watts)
4 x Tweeters (4 ohm/40 watts)
4 x 2-way Crossover Network (40 watts).


Total wattage is 480 watts

Please tell me how I can feed the power supply to these two stereo amplifiers (240 watts each) from a single power supply source like an AC adaptor (24V / 6A) only. I don't like to use any kind of transformer for it.

Just help me!
 
Last edited:

Les Jones

Well-Known Member
Most Helpful Member
You are not clear if the power ratings are the output power of the amplifiers or the power input requirements of the amplifiers. Do all the amplifiers require the same supply rail voltages ? An AC adapter will contain a transformer. This may be a mains frequency transformer or a high frequency transformer if it is switched mode.)
24 volts at 6 amps is only 144 watts and it is unlikely that the amplifiers will work with a single supply rail. Most amplifiers require a split power rail. You will need to give FULL details of the amplifiers power requirements to get a sensible answer. Why are you wanting to avoid power supplies that use transformers ? What is your primary power source ? (AC or DC and what voltage and current rating ?)

Les.
 

learning

Member
You are not clear if the power ratings are the output power of the amplifiers or the power input requirements of the amplifiers. Do all the amplifiers require the same supply rail voltages ? An AC adapter will contain a transformer. This may be a mains frequency transformer or a high frequency transformer if it is switched mode.)
24 volts at 6 amps is only 144 watts and it is unlikely that the amplifiers will work with a single supply rail. Most amplifiers require a split power rail. You will need to give FULL details of the amplifiers power requirements to get a sensible answer. Why are you wanting to avoid power supplies that use transformers ? What is your primary power source ? (AC or DC and what voltage and current rating ?)

Les.
The main reason for not using a transformer is that it is bulky and needs more skill to control the humming sound from the amplifier, as I have a lot of bad experience with it from my past work.

My primary power source is AC (220 volts) and the current is 50 cycles per second.

The amplifier details are 2x120 watts per amplifier, and the total two amplifier wattage is 480 watts.

Please advise me.
 

Ramussons

Active Member
Could you tell me how to power up two stereo audio amplifiers from a single source of power supply?

Configuration:


4 x Woofers (4 ohm/20 watts)
4 x Tweeters (4 ohm/40 watts)
4 x 2-way Crossover Network (40 watts).


Total wattage is 480 watts

Please tell me how I can feed the power supply to these two stereo amplifiers (240 watts each) from a single power supply source like an AC adaptor (24V / 6A) only. I don't like to use any kind of transformer for it.

Just help me!
These are the Power Ratings of the Speakers, not the amplifiers.
What are each amplifier output / input power ratings?
 

Les Jones

Well-Known Member
Most Helpful Member
So can you confirm you need a power supply capable of supplying 24 volts at 20 amps (480 watts ) ?
You should be able to obtain a switch mode power supply capable of supplying this BUT it will contain a transformer working at several tens of Khz.

Edit. Looking at your post #1 you list the crossover networks as taking power. A crossover network normally takes the output of a power amplifier and filters the high frequencies to the tweeter, the mid frequencies to a mid range speaker and the low frequencies to a woofer. Another way this can be achieved is to have a power amplifier for each speaker and do the filtering at the amplifier inputs. Can you give the FULL INFORMATION on the amplifier setup ?

Les.
 
Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
So can you confirm you need a power supply capable of supplying 24 volts at 20 amps (480 watts ) ?
You should be able to obtain a switch mode power supply capable of supplying this BUT it will contain a transformer working at several tens of Khz.

Edit. Looking at your post #1 you list the crossover networks as taking power. A crossover network normally takes the output of a power amplifier and filters the high frequencies to the tweeter, the mid frequencies to a mid range speaker and the low frequencies to a woofer. Another way this can be achieved is to have a power amplifier for each speaker and do the filtering at the amplifier inputs. Can you give the FULL INFORMATION on the amplifier setup ?

Les.

I don't think he's got the slightest clue what he's on about - and his power figures are completely imaginary - you don't get 120W off 24V - you only get (a theoretical maximum of) 18W in 4 ohms, or 72W if you bridge two amplifiers (and the amps are 2 ohm capable).
 

Les Jones

Well-Known Member
Most Helpful Member
Hi Nigel, It was thinking about how he could get 120 watts from a single 24 volt supply that made me re read post #1 again. Then seeing a crossover network consuming power made me think we were not being told the truth about the system.

Les.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Hi Nigel, It was thinking about how he could get 120 watts from a single 24 volt supply that made me re read post #1 again. Then seeing a crossover network consuming power made me think we were not being told the truth about the system.

Les.
That's just the way he's written it - the crossover is presumably rated at 40W power handling. Which is rather low for a supposed 120W amplifier.

Basically nothing makes any sense, we've got no details at all, and no real idea what he's trying to do - other than none of his figures are real.
 

AnalogKid

Well-Known Member
Most Helpful Member
Please tell me how I can feed the power supply to these two stereo amplifiers (240 watts each) from a single power supply source like an AC adaptor (24V / 6A) only.
You can't.

24 V x 6 A = 144 W. From that you subtract the inefficiencies of the amplifiers. Even if they are super-efficient class D types, that still costs you 10%. That leaves an absolute best case of 130 W total for all channels.

Then you have to deal with the issues raised above, that 24 V peak-to-peak is not enough to drive the speakers you have to the power levels you want.

ak
 

rjenkinsgb

Well-Known Member
Most Helpful Member
4 x Woofers (4 ohm/20 watts)
4 x Tweeters (4 ohm/40 watts)
4 x 2-way Crossover Network (40 watts).

If the crossovers are rated at 40W, that is the maximum power you can put through them from the amps....

4 x 40W = 160W total for all four channels.

The crossovers split the input power between the woofer and tweeter, depending on the frequency content.

Also you do not say if the power ratings of the parts are peak or RMS. Many suppliers use peak or PMP etc., which is an imaginary advertising number.

The _only_ rating that matters is the RMS power, with audio amplifiers or speaker components etc.
 

Ramussons

Active Member
The amplifier's output power rating is 120 watts, and the amplifier's input power rating is 24 volts at 5 amps.
Now the Power input to the amplifier is 120 watts. That is the max power input when the amplifier is on full blast.
For powering 2 such amplifiers, you will need a power supply unit capable of delivering 24 Volts @ 10 amps.
You will need 2 Isolation diodes rated 10 Amps @ 50 volts with low voltage drops. You can use a suitable MosFets for the same.
 

Diver300

Well-Known Member
Most Helpful Member
For powering 2 such amplifiers, you will need a power supply unit capable of delivering 24 Volts @ 10 amps.
You will need 2 Isolation diodes rated 10 Amps @ 50 volts with low voltage drops. You can use a suitable MosFets for the same.
I can't see why diodes would be needed. When running loads, in this case the amplifiers, in parallel from one supply, diodes aren't normally used.
 

audioguru

Well-Known Member
Most Helpful Member
Amplifiers from ebay can be powered from 24VDC and can produce any high number of phony Watt numbers.

A stereo amplifier made properly and with a class-D TPA3116 IC produces 30 real Watts per channel at low distortion into two 8 ohm speakers or produces 50 real Watts per channel into two 4 ohm speakers. The amplifier has bridged output wiring.
Powered from 24VDC, the TPA3116 amplifier produces a total of 120 PEAK Watts into 8 ohm speakers with very high distortion. Peak Watts are simply doubled real Watt numbers. High distortion adds additional power.

The class-D produces an additional heating power of only 10% of the power numbers.

I agree that a passive crossover network uses no power but the amplifier can use an 8 ohm woofer and an 8 ohm tweeter at the same time which results in a 4 ohm load.

All home and pro amplifiers are powered from a transformer and produce no hum sound because the power supply is properly filtered and the input cables are shielded audio cables.

Bridged amplifiers usually use a single polarity (not a split polarity) power supply.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I agree that a passive crossover network uses no power but the amplifier can use an 8 ohm woofer and an 8 ohm tweeter at the same time which results in a 4 ohm load.

Not at all true, a decent crossover with 8 ohm speakers produces an 8 ohm load - there may be a dip around crossover frequency, but this is probably less than the dips on the individual drivers, and still results in an over all rating of 8 ohms.

And while a crossover doesn't 'use' power, it does waste some of the power passing through it.
 

audioguru

Well-Known Member
Most Helpful Member
What I was saying is that a 2-way speaker can play a low frequency from the 8 ohm woofer plus play a high frequency from the 8 ohm tweeter at the same time. Then for that moment the total load is 4 ohms.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Then for that moment the total load is 4 ohms.
No.

That is like saying a single wide range 8 ohm speaker is magically 4 ohm if you put two different tones through it simultaneously.

As each crossover transition is gradual and if you graph it against frequency, the series impedance to any one driver will start to increase well before the next unit takes over.

Both will have added impedance at the changeover points, keeping the amp load near constant if everything is properly matched; in practice it seems more likely to result in slightly higher impedance near the crossover frequency,

No even a really cheap crossover should have low impedance to two different drivers at any frequency!

Example plots for a well matched system - impedance

sin_imp_+12dB_V5_20mm vent.jpg


Output level

FR_drivers_+summed.jpg
 

audioguru

Well-Known Member
Most Helpful Member
I did not say that one 8 ohm speaker is 4 ohms when it produces two frequencies.
Instead I said that an 8 ohm woofer plus an 8 ohm tweeter both playing tones in the middle of their frequency ranges are a load of 4 ohms on the amplifier.

The crossover network does not prevent the tweeter from playing a high frequency when the woofer is playing a low frequency and visa-versa.
 

Latest threads

New Articles From Microcontroller Tips

Top