The right audio amplifier?

Good evening,

I created a bluetooth speaker project with a few other features. I have already bought a mini speaker but in order to improve and change.
Its speaker is of very poor quality and does not play loudly. So I’m going to switch to a better speaker (very old but better anyway).

Of course this therefore requires an audio amplifier to increase the power.
But I don’t know what kind of amplifier to choose. Can you help me ?

I would like it to work with little voltage (1 or 2 18650 batteries considered).
I only use one speaker.

Do you think 20w is enough?

I found nothing else that could match, is the Tpa3110 suitable?

20W will be plenty loud! Plenty!

Thank you for your reply.
Really ? I took an example from the JBL flip 5.
Do you think that 10 or 15 w or less is already very strong?
So much the better that I don’t need that much.
In this case what would you recommend to me?

Yes, really! Obviously it depends entirely on the listening circumstances, but if you just want to listen to music in your living room or office, then you should be thinking in terms of single digit watts.

I would also add that I don’t think there’s any way that speaker you’ve shown us would handle 20W. Also, it isn’t remotely going to be hi-fi sound reproduction, so you don’t need to worry about loads of “headroom” in order to keep the harmonic distortion vanishingly low, or anything like that.

And may I also point out that one or two 18650 batteries will flatten in an hour or so if you’re thinking of using anything like 20W.

Anyway, I’m sure you’ve got the message! :grinning:

I used these little speakers with a 12V supply and transistor to make a Arduino generated warble sound (just switching between two tone()s - and ended up putting a large resistor in series with it to quiet it down it was so loud.

Do you have a link to that Tpa3110 board?

Thank you for responding to me so quickly.

Ok I understand. :wink:

From what I just looked at the 60 and 100w are commonplace but below 20w in mono. I only see 5 and 2,5w which seems very little.
Do you have any in mind for me?

It was that but suddenly it is in 60w.

Ok, two 18650 in series supply say 1A of current at 7.4V.
(Speaker with 8 ohm impedance, supplied with 8 ohm source, will draw around 1A: V= I x R, or V/R = I, 7.4V/8 ohm = 0.925A. If you want more current flow, you need a higher voltage, or a lower impedance speaker - like 4 ohm)
P = I x V, 1A x 7.4V = 7.4W.
If you want louder, you use more battery current, which results in shorter run time.
A speaker with high sensitivity will seem louder than one with low sensitivity. Perceived loudness will also be frequency dependent.

May I ask where you intend to use it? Outside or indoors? How much other noise is there in the room? How big is the room? Will it be background music? Announcements? Focused music listening?

It will be almost entirely to be used indoors. I plan to use it for background music but also for focused music (for a party for example).
So I found the one that would match more. Does it look good?
LM386 10 W

You might be better with a “portable rechargable speaker”

They don’t cost much and can play 20 hours on a charge.

I still make a little savings, you have to buy an amplifier for about 5 euros.
In addition I intended to work on the design and then I learn by creating this speaker.

What do you think of the LM386 which does 10w?

Do you want good sound quality?

Don’t forget you are also paying for shipping and perhaps VAT.

There’s a LOT to consider here…

A “small” speaker is probably similar to what’s in your TV except your TV is probably stereo and there might be separate tweeters for better high frequencies.

I’m probably “using” about 1 Watt when I’m listening to my TV quietly-normally. And that would be OK for “background music”.

But when I turn on my surround-sound receiver and 15-inch subwoofers to watch a movie or video concert “the sky’s the limit”. But, I don’t have it cranked-up all the way and I don’t want to annoy the neighbors so I’m not using the hundreds of watts available.)

Doubling the power is +3dB which is “noticeably louder” but not tremendously louder. That’s why you can easily get into the “big watts”, especially if you want deep-strong bass.

What you have isn’t adequate for a “party” unless maybe if it’s background music for a “nice classy” dinner party. But several people talking at the same time can get rather loud so you have to turn-up the music to hear it. And you’ll probably want stereo.

For good bass you need to “move lot’s of air”. That means a big speaker/woofer, a big amplifier, and a big cabinet. Flat screen TVs (and laptops) usually have lousy bass because they have small speakers in a fairly-small cabinet.

Speaker design is complicated so this is over-simplified but the soundwaves from the back of the speaker are out-of-phase with the waves from the front so they tend to cancel-out, especially at low frequencies. The cabinet helps with that and a bigger cabinet means the speaker can move more freely without trying to compress the air inside as much. “Ported” speakers are “tuned” to phase-delay the bass waves from the back to reinforce the main waves at the tuning-frequency.


The LM386 chip is more like 1W or less. (Check the datasheet for the actual chip.)

Amplifier power is often limited by the voltage. (High power car amplifiers have a built-in voltage booster.)

It’s the RMS voltage that’s important. For example, with a “regular” single-ended amplifier (like the LM386) you can’t more than 12V peak-to-peak. (In the real world you’ll loose a little voltage because there is voltage drop across the amplifier circuitry.) That’s 6V peak. The “formula” for RMS is 0.707 x peak so that’s about 4V RMS. (You can use a factor of 0.354 X the power supply voltage, and a spreadsheet is handy.)

There a couple of ways to calculate power but this is handy:
Power (Watts) = Voltage (squared)/Resistance. Just remember that’s RMS voltage.
So with the 12V power supply we can get about 2 Watts into 8-Ohms or 4W into 4-Ohms.

With a bridge amplifier where both speaker terminals are driven in opposite directions you get double the voltage for 4 times the power.

Most modern audio is stereo (different sound coming from left & right). If you want to use a mono speaker the left & right signals should be mixed. That’s easy to do in analog, it’s easy to do digitally if you are doing your own digital audio processing, or it’s pretty to make mono copies of your MP3s, etc.

But if you are streaming music with your phone through Bluetooth it might not be so easy, There MIGHT be a mono setting in your phone software.

Thank you very much for your very detailed response.

For mono I don’t think there is a problem since it is the mini-speaker that does this part of the job for me, and it works well (except for the quality and the volume of the blow). If I want to add an amplifier it is to increase the power of the sound.

For the calculation, it seems logical but I do not understand then why the LM386 board product description mentions this: Operating voltage: DC 3V ~ 12V;
Output Power: 0.5W-10W
So it should be able to do 10w?

My speaker is about the same size as the speaker speakers for the speakers I already own, with wires, and I’ve never needed to max out. So it should be good at this level

How do I solve my problem?

Yes I would rather have quality sound. Depending on the amp I take it should not cost more than 7 euros all inclusive.

No, you can’t get to even 1W with an LM386. Its also an obsolete chip. That product
description is fraudulant.

Why not go for a medium output class D chip like the TPA3116D - plenty of modules
for this.

The LM386 is a very poor choice if quality or volume is any concern whatsoever. It’s more like 0.25W and then it becomes a fuzz pedal. Even at low volume it sounds terrible. There are a million better options.

Keep in mind, regarding wattage and listening volume level, anything battery powered is low-wattage, but that’s ok because 1W is loud.


Excuse me for responding so late.

Okay for the LM386, I won't take it.

You offered me the TPA3116D, isn't it too powerful compared to what I was told previously? It is rather made for large speakers. Could it work with two 18650 batteries.

And what do you think of pam8403?