I think he means that his 13.2V battery (two lead-acid 6V batteries in series) can supply 3A. But the max amplifier peak output current will not be 3A, it will be about (13.2V - 3V)/2= 5.1V peak/4 ohms speaker= 1.28A and the max output power will be (1.28A x 0.707) squared x 4 ohms= 3.6W RMS. The amplifier will heat with 1.4W. If he bridges two of these amplifiers then the peak output current will be 1.28 x 2= 2.56A and the output power will be about 12.6W. The amplifier will heat with 5W.

The average power from the amplifier will be about (3.6W + 1.4W)= 5W x 0.1= 0.5W if the amplifier is not bridged and is playing music so it is almost clipping. Then the average battery current will be about 120mA (a guess). A 7Ah battery charge will last 7/0.12= 58.3 hours.

Calculate how long the battery charge will last yourself when the amplifier is bridged.

Thank you. Want you and everyone to know none of this will be wasted. I will be studying everyone's equations. Also what circuit were you referencing in this post?

 

what circuit were you referencing in this post?

It hasn't been designed yet. Two complementary power transistors and two or three little NPN transistors.

 

What @Audioguru means is that it doesn't apply to any one design. It is the basic analysis of any audio amplifier with a push-pull output stage.

 

It hasn't been designed yet. Two complementary power transistors and two or three little NPN transistors.

If tip41/42 with c1815(have a lot of these as well) would work I'd create it. If you had an idea for a schematic I might be able to create it just from experiments with different values of resistors and caps.

 

What @Audioguru means is that it doesn't apply to any one design. It is the basic analysis of any audio amplifier with a push-pull output stage.

As I asked Audioguru if you have a rough schematic I'll try to make it and see how it goes if it's possible with tip41/42 and c1815s. I have plenty of both.

 

It hasn't been designed yet

Actually it has been! The "Lil Tiger"
How many times do I have have to mention this.

 

Actually it has been! The "Lil Tiger"
How many times do I have have to mention this.

AHHHHHHH! I WILL BUILD IT! ALSO I DON'T KNOW HOW TO MAKE EMOJIS ON HERE! FRUSTRATED AND HAPPY YALL ARE HELPING ME FACES!!

 

The Lil Tiger in post #110 produces 5W into 8 ohms when powered from 24V but do you want to carry around four 6V lead-acid batteries?
With two 6V batteries producing 13.2V I calculate an output of only 1.1W into 8 ohms because the design is using darlington transistors that have a lot of voltage losses.
A 4 ohm speaker would almost double the power to 1.9W.
Bridging two of these amplifiers would produce about 6.7W into 4 ohms with a 13.2V supply.

Compound transistors should be used for less voltage loss and fewer diodes. Then it will produce much more power.

 

The TS claimed he would use 18 volts. At this voltage the power out is just under 4 watts at 4 ohms
SG

 

Compound transistors should be used for less voltage loss and fewer diodes.

That's true but is the example you posted correct? Seems like that would only work using a dual supply maybe. I can't find any examples of that type of output configuration.
Below I posted a working circuit using a different compound configuration driven by a LM386-4, 2.125 watts at 12 volts and 5.5 watts at 18 volts with a 4 ohm load.
SG

 

Hello,

I just came accross a weird schematic that uses an opamp as driver for power transistor (founs in electuur):



They claim an output power of about 6 Watts @ 0.01 %

Bertus

 

Doesn't seem like much power for a 36 volt power supply.
SG

 

Boy oh boy I made a messy error on the compound transistors, I corrected it.

Elliot sound Products has many audio projects and uses single supplies and dual polarity supplies on them. Some use compound transistors.

Many power amplifier ICs have datasheets that show booster transistors at the positive and negative supplies for the IC like this one that produces 29W at low distortion into 4 ohms, or maybe 16W into 8 ohms.

 

The problem with using an opamp or an LM386 power amp to drive emitter-follower transistors or compound transistors is that the opamp and LM386 already have the voltage loss of emitter-follower outputs. Then the voltage losses are doubled resulting in less output power.

 

The Lil Tiger in post #110 produces 5W into 8 ohms when powered from 24V but do you want to carry around four 6V lead-acid batteries?
With two 6V batteries producing 13.2V I calculate an output of only 1.1W into 8 ohms because the design is using darlington transistors that have a lot of voltage losses.
A 4 ohm speaker would almost double the power to 1.9W.
Bridging two of these amplifiers would produce about 6.7W into 4 ohms with a 13.2V supply.

Compound transistors should be used for less voltage loss and fewer diodes. Then it will produce much more power.

I wouldn't mind bridging them for less battery weight, also i should have mentioned that when I said carry around, I really meant it'll be on casters like a rolling luggage bag. My apologies but I use 3/4in birch for all my "pretty" wood projects and that stuff is heavy. Most everything like you're used to seeing in prefab speaker boxes is particle board with a plastic or thin wood veneer making it very light. If I build it, it will be quite solid. So more batteries aren't an issue. Even with just 2 it'll weight around 30lbs. However if you know a circuit that would work about the same with a 12volt supply I'll try it as well.

 

I wouldn't mind bridging them for less battery weight, also i should have mentioned that when I said carry around, I really meant it'll be on casters like a rolling luggage bag. My apologies but I use 3/4in birch for all my "pretty" wood projects and that stuff is heavy. Most everything like you're used to seeing in prefab speaker boxes is particle board with a plastic or thin wood veneer making it very light. If I build it, it will be quite solid. So more batteries aren't an issue. Even with just 2 it'll weight around 30lbs. However if you know a circuit that would work about the same with a 12volt supply I'll try it as well.

Also I'm not sure what you mean by compound transistors?

 

The problem with using an opamp or an LM386 power amp to drive emitter-follower transistors or compound transistors is that the opamp and LM386 already have the voltage loss of emitter-follower outputs. Then the voltage losses are doubled resulting in less output power.

Not really. The LM386 worked better than a single transistor driver. The output from the TIP drivers clipped before the output of the LM386.
SG

 

Also I'm not sure what you mean by compound transistors?

See post 213.
SG

 

OK wow. I have seriously been missing a lot of posts on my thread. I just read 6 I never got alerted to and never noticed and they are at the same time of some of my posts. I'm going to apologize if I've repeatedly asked the same thing over because I'm getting posts hours after the time stamp

 

I have seriously been missing a lot of posts on my thread

Well when you get over 200 post it happens.
SG