volage-regulating an amp

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mike_canada

Joined Feb 21, 2020
239
Some may have seen my attempts at building a good discrete amplifier on here, but I thought of something.

Maybe making the current limiting resistors lower and lowering the supply from 7.2V or 14V down to 5V but this supply would be fed though a 7805 or similar regulator.

I asked this because I ran my older amplifier model (no bridging) and on a fresh battery the sound is nice and loud but on a battery that's half dead, the sound has more distortion and is quieter, and by lowering voltage and resistor values (slightly), I may get better sound volume and probably no heat from the transistors.

I did a simulator test on my latest model with 5V supply and 56 ohm resistors in my bridged class AB amp and the output currents are 283mA and converting that to wattage means under 2 watts which allows the power transistors to run without heat sinks.

So I'm thinking if I make my source say 14.4V and give the amp circuit power through a 5V regulator fitted with a heavy heatsink then as the battery is losing power the audio volume stays the same for a little longer (at least until the 14V source drops below 5V).

And I'm thinking if this way works, I might have to find a regulator with higher specs.

So is it sensible to use a regulator here or would that be a waste?
 

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DickCappels

Joined Aug 21, 2008
10,121
With that ratio of input voltage to output voltage you would be using about 2/3 of the power from the battery to heat of the regulator. A simple buck converter could improve the power conversion efficiency to around 90% pretty easily.

A "linear" regulator with heatsink is a valid solution, but your batteries would last longer with a switching supply.

When you talk about current and power, it sometimes helps if people know what kind of signal it is: RMS, Avarage, P-P, etc.
 

MrChips

Joined Oct 2, 2009
30,449
You are tossing around multiple ideas in an attempt to increase output power at low supply voltages without using heat sinks. All of these ideas are counterintuitive, counterproductive, and in conflict with one another.

You choose to do something because “someone says…” without sitting down and doing the math or the practical electronics.

What you are attempting to accomplish has been solved many times before by people who understand audio acoustics and electronics.

I would be happy to assist you in reaching your goal if you would stop doing what you are doing and listen and follow some sound advice.
 

Ian0

Joined Aug 7, 2020
9,453
It is generally accepted in the field of audio amplifier design that a regulated supply is unnecessary.
A good amplifier design will not suffer from variations of bias current due to changes in the supply voltage, and has a very high PSRR, which prevents ripple on the supply from appearing on the output.
 

Jolly13

Joined Mar 25, 2018
18
mike_canada Have seen some other threads you are refer to. No magic hear, a battery only has so much power it can provide , changing base voltage will just use power in DC space. Couple with the volume you want from that speaker requires a constant amount of power.

More efficient speaker.
or more efficient audio amp.
more power source.
 
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