Help With Low Cost Amplifier

[william444555]

I bought a load of cheap $1 amplifiers from eBay so if they break they will not break the bank, i have seen pages on bridging amplifiers but how does that exactly work, i would like these to power a couple of sub-woofers. how would i bridge them and how does bridging work?

 

[KatieandDad]

https://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers

 

[Nigel Goodwin]

I bought a load of cheap $1 amplifiers from eBay so if they break they will not break the bank, i have seen pages on bridging amplifiers but how does that exactly work, i would like these to power a couple of sub-woofers. how would i bridge them and how does bridging work?

Bear in mind they might already be bridged (a lot of small and cheap IC's are bridged ones) - and you can't bridge bridged amplifiers.

 

[william444555]

Bear in mind they might already be bridged (a lot of small and cheap IC's are bridged ones) - and you can't bridge bridged amplifiers.

Ha, i tried bridging it and it sounded worse then without bridging, it clipped whatever volume it was on but then i unbridged it and sounded fine, thanks anyway

 

[JMFahey]

Just curious, any links?
And how are they powered?

If they are, say, 1W amps fed from a 9V battery, bridged or not they won't help much powering a *subwoofer* which by definition is power hungry.

 

[william444555]

Mini Digital DC 5V PAM8403 Audio Amplifier Board Class D Kit Module 2*3W | eBay
5v usb power, 2x3w and it does power the sub fine and it can drive it to clipping, it is a 30w sub too!

 

[poynton]

A quick search of the net reveals that you cannot bridge the outputs to increase the power output BUT according to the manufacturers you can increase the power output by increasing the supply voltage to +9v and lowering the speaker impedance to 3ohm.

Personnally, I would glue a heatsink on the chip before doing this.


Andy

 

[JMFahey]

Well, let's not be way too optimistic:

Datasheet http://www.diodes.com/_files/datasheets/PAM8403.pdf says:

1) absolute maximum voltage : 6V
2) recommended not to surpass : 5.5V
3) power at clipping: 2.5W RMS into 4 ohms , per channel
4) each channel is already bridged.

As of the 30W subwoofer, the amp itself starts clipping above 2.5W RMS, so any clipping you hear comes fromm the amp, not the speaker.

That said, it looks like a fun project, will probably get a couple myself and experiment.

Just won't carry it to a car SPL competition

 

[poynton]

https://www.google.co.uk/url?sa=t&r...y36u1E8Ot2rRfS_jo4CEoA&bvm=bv.104317490,d.bGg

 

[kenpeter]

These amps might be better matched to small drivers in an array.

Maybe something like this:
http://www.parts-express.com/at-521...e-woofer-with-rubber-surround-4-ohm--299-2148

Even $7.88 per woofer is hard to justify against an amp thats only $0.50 per 3W channel.

 

[william444555]

Thanks everyone for the help!

 

[JMFahey]

https://www.google.co.uk/url?sa=t&r...y36u1E8Ot2rRfS_jo4CEoA&bvm=bv.104317490,d.bGg

Well, they confirm you can't rise voltage on the PM8403 , nor bridge them nor lower load impedance.

 

[poynton]

here's the response I got after emailing Diodes:

We would advise NOT to connect the two outputs of PAM8403 in parallel. We recommend two ways to get higher power :

a ) increasing the supply voltage, from 5V to 9V for example---PAM8320 working at 4.5V to 15V is a good candidate for this solution.

b) reduce the loading impedance, from 4Ohm to 3Ohm for example---PAM8406 can drive as low as 2.5Ohm/Ch that make PAM8406 is a good choice.

 

[djk]

"and you can't bridge bridged amplifiers. "

Crown does.

It's not hard, but you have to know how to do it.

 

[JMFahey]

.......

Sorry, your comment didn't come through.
Your point is ..... ?

 

[JMFahey]

"and you can't bridge bridged amplifiers. "

Crown does.

It's not hard, but you have to know how to do it.

Yes, I know how to do it, and it does not apply here.
Do you know why?

 

[djk]

He probably has only one supply,

however,

others may not have this limitation, or may need current rather than voltage.

 

[wg_ski]

"and you can't bridge bridged amplifiers. "

Crown does.

It's not hard, but you have to know how to do it.

But if you're starting with a little kit, whose input is ground referenced, you're pretty well screwed. Unless you're willing to resort to the use of input transformers.