Modifying amplifier for more output power?

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Hello,
I would like to know if car amplifier can be modified to deliver more output wattage?

I`m aware of other methods to get more power, like using lower impedance driver, higher sensitivity driver,...

The first thing that should be done is to bridge two channels together... ok, this gives a lot more power, but after that you're done, this is the max power you will get... or is it?

I did a research on the internet and didn`t found any useful information about modifying amplifiers...

Changing output transistors by itself obviously wouldn`t change anything.

But upping the rails voltage surely would... Let`s say from 30-0-30 to 40-0-40. I think that 20v peek to peek would be a good value and theoretically about a 30% increase of output power.

First challenge is to up the voltage coming from SMPS.
1.) Should this be made by changing number of coil turns on the transformer or are usually there any other voltage limiting components that could be changed?
2.) I`m aware that capacitors would need to be changed for higher voltage ratings, are there any other components that would need to be looked after and changed?

Now to the actual amplifier part:
1.) Capacitors would need to be replaced with higher rating ones.
2.) Transistors would need to handle more power, but if amplifier is rated 2ohms stable and only 4ohm drivers would be connected to it there is no need to change them, except if amplifier would be wired in bridged configuration?

After the modifications temperature should be monitored and heatsink would need to be upgraded is needed.




When looking at datasheets of various ICs I can see that maximum operating voltages are always much higher than recommended ones are. Amplifiers using ICs are usually designed using recommended voltages rather than close to maximum ones. Would this be the same for car transistor type amplifiers? I guess so because manufacturers want to be safe, amplifiers can hold more abuse, etc...


What do you think of this? Any ideas, recommendations, any precautions to keep components safe from getting damaged?
 
After some digging I have found formula for calculating peek output power
P=v^2/R
P=v*I

Amplifier that I would like to modify uses D718 and B688 transistors. They can handle 120 peek to peek and 8A.

In perfect world without losses you could get 225w peak without current limit at 4ohm and 30v.

With 40v it would be able to produce 400w, but because transistors can only handle 8A it would be able to produce 320W peak.

Is this telling me that I should not increase voltage that much without changing transistors? And I should increase it only to 35v where amplifier would produce 306,25W peak (better to leave a little headroom to 320w peak)?
 
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As you have found yourself just by thinking about it in your first two posts, it is really not that simple and you're effectively building a new higher powered amplifier. Another option would be just to duplicate everything, that is, more amplifiers powering more speakers. It would be simpler, safer and probably cheaper in the long run
 
As you have found yourself just by thinking about it in your first two posts, it is really not that simple and you're effectively building a new higher powered amplifier. Another option would be just to duplicate everything, that is, more amplifiers powering more speakers. It would be simpler, safer and probably cheaper in the long run

Yes, you are right, but I don`t need more power, I have 2 x 550rms @4ohm in my car, 2 x 720w power amplifier at home and a few spare ones...
I wan`t to modify one just for fun and education.
 
You have to rewind the power supply transformer, to get a higher rail voltage. For sure everything else in the power supply and amplifier stages must work within its power limits.

Thats the anwser I was hopping for.
Do you know if voltage will rise linearly to number of coil turns or do I have to do all the complicated math to find out how much turns I must add for desired voltage?

Thank you
 
In principle the voltage will change linearly. But real world applications are not so straight forward. So...

No, it is rather unlikely that the voltage will increase simply because you throw on a few extra turns to a transformer in a SMPS. Unless the SMPS in the amplifier is completely unregulated, significantly over sized and extremely tolerant to things being fiddled with. Which switching power suppliers are infamously not.

You will find that if you managed to pull it off, this sort of change would:
- Increase the primary current in the SMPS
- Require protection and fusing to be changed
- Affect dissipation in the primary drivers (possibly not such a big deal)
- Increase the core flux, and possibly drive it to saturation
- .....

It might be spectacular, and make a great youtube video though. :)

I recommend that you start with something a touch less challenging than a power amp with SMPS driving the rails, once you get your head around the impact on the output stages and are comfortable there, I would take a (very) tentative step into the curious world of switching power supplies.
 
Hello, why not?
1. Because amplifiers are already highly optimized and close to its max possible output. You need to change almost everything, so that is not a modification, but a new amplifier.
2. Because any modification demand excellent knowledge about amplifiers.

But upping the rails voltage surely would... Let`s say from 30-0-30 to 40-0-40. I think that 20v peek to peek would be a good value and theoretically about a 30% increase of output power.
Wrong. Theoretically it would be over 70% increase of output power.
See the point 2. above.

After some digging I have found formula for calculating peek output power
P=v^2/R
P=v*I
If you learned this formula recently, please, please forget about modifying amplifiers any time soon. Take your time and patiently learn about amplifiers, audio is a great hobby.
 
Like any piece of equipment, its components (even the heatsink) are chosen to be the best choice for the designed power output.

Modifying an amp will require compromises. The most likely is that you'll turn the amp into something that can run at full power for a limited time. Think grand touring vehicle vs dragster.
 
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