• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Adapting a pair speakers salvaged from a defunct TV

Buk

Member
I bought a new monitor for my PC, but as I wanted one that supported portrait mode, it had to be a business model that doesn't have built-in speakers.

I have a pair of 10W speakers that came from a defunct flat panel TV, and I would like to adapt them for use with the line out from my PC.

The speakers are labelled 6 Ω / 10W and measure 8.6 Ω (static DC) resistance.

And that is about as far as my thinking has gone. I doubt that the output from the line-out jack will be sufficient to drive the speaker directly, so I assume I will need some kind of small amplifier. The monitor has a USB 2.0 hub which could provide a conveneient source of 5V but only 500mW which may bot be enough?

Any pointers or suggestion on how to do this would be useful.

Thanks, Buk

Let me know if I can supply any further information.
 

audioguru

Well-Known Member
Most Helpful Member
USB 5V and only 500mW are getting close to headphones level.
My pc audio system has a 12V/1A (12W) power supply. 3 real Watts into each stereo speaker (6W total for sound) plus another 6W of heating.

Some modern little stereo amplfiers (PAM8403) heat only a little and produce 2W into each 6 ohm speaker when the power supply is 5V/1A (10 times your USB current).
 

Buk

Member
Unc,
Thanks for the feedback. (Warning! I know just enough about electronics to be dangerous.)

Looking at the specs for the PAM8403:
Code:
PAM8403 Audio Amplifier Module Specifications

    2 channels 3 W PAM8403 audio amplifier
    Output Power: 3 W + 3 W (at 4 ohm)
    Working Voltage: 2.5 to 5.5 V
    Board Size: 24 x 15 mm
    High amplification efficiency 85%
    Unique without LC filter class D digital power board
    Can use computer USB power supply directly
That last line makes it sound ideal for my needs; but I assume that to get the 6+ Watts of power, they must mean a USB 3.x; not the USB 2.0 available from the monitor?

I have a coupe of spare USB 3.x sockets on the PC; not as convenient, but doable.
 
Last edited:

audioguru

Well-Known Member
Most Helpful Member
A Chinese module with a real (not copy) PAM8403 in it is cheap. Get one and try it. You might find that it is not loud enough.
Then find one that produces 30 Whats or 20 low distorting Watts per channel which will sound twice as loud as the 2 Watts per channel.

Twice the power sounds only a little louder since the sensitivity of our hearing is logarithmic. 10 times the power sounds twice as loud.
 

Buk

Member
OKay, thanks for the clarification, but...
The PAM8403 datasheet says:"
Code:
Supply voltage Range........................       2.5V to 5.5V
Max. Supply Voltage (for Max. duration of 30 minutes)
..........................................................6.4V
Which to me suggests that the 5V from USB is the perfect voltage?

As for power, the Wikipedia page for USB 3.x suggests "

For high-power SuperSpeed devices, the limit is six unit loads or 900 mA (4.5 W)—almost twice USB 2.0's 500 mA.[10]:section 9.2.5.1 Power Budgeting

USB 3.0 ports may implement other USB specifications for increased power, including the USB Battery Charging Specification for up to 1.5 A or 7.5 W, or, in the case of USB 3.1, the USB Power Delivery Specification for charging the host device up to 100 W"

Note: I'm not looking for HiFi or Surround Sound here. Just the ability to hear speach and backgound music in a quite home office.

If a combination of PAM8403 + USB is not sufficient, then can you suggest something better?
 

audioguru

Well-Known Member
Most Helpful Member
Try a PAM8403 module to see if it is adequate. If not then there are hundreds of more powerful amplifier modules available.
There are many fake or defective electronic items sold "over there" at ebay, AliExpress, Banggood and Amazon. Walmart and Parts Express might sell better ones.
 

Buk

Member
"Try a PAM8403 module to see if it is adequate. If not then there are hundreds of more powerful amplifier modules available. "

I only considered this module because you mentioned it; if it is no good, why did you do that?

I came here to get advice, not be sent on a suck it and see adventure that will likely as not waste both my time and money.

I guess I'll go look for an electronics forum populated by helpful -- probably european -- adults; not a bunch of typically xenophobic,
american children.

(Don't bother banning me; there isno reason for me to come back here.)
 

audioguru

Well-Known Member
Most Helpful Member
What is your problem with trying a PAM8403 module? It might be fine. I do not know how much power (loudness) you want, you should know.
You
said you wanted to power an amplifier with USB 5V. If you want more power then you need a higher supply voltage and more current than USB provides.
I mentioned the PAM8403 because it is designed to use 5V or less.

You will find me on many other Worldwide electronics forums. I am not an American.
 

Visitor

Well-Known Member
I guess I'll go look for an electronics forum populated by helpful -- probably european -- adults; not a bunch of typically xenophobic,
american children.
Audioguru is one of those "polite" Canadians.

Many of the "most helpful members" here are European.... a rating based solely on the number of posts.
 

Buk

Member
I was wrong. I did have a reason to come back -- I forgot to cancel the email notifications.

You'll note I did not upper case the 'a' -- I guess I could have prefixed it with 'north', but that is pretty much implied by his reference to "Walmart".

As for my "problem with trying a PAM8403 module"; why waste time (3 to 4 weeks delivery) and money(albiet not a lot) on that, when I can go for (say) this, have it delivered tomorrow and working by Tuesday using an old 12v/4A laptop brick.

I was not contradicting the USB ain't enough; I was looking for clarification from experts; not suck-it-and-see/told-you-so wannabes.
 

audioguru

Well-Known Member
Most Helpful Member
Yes, some American stores were in Canada. Sears and Radio Shack are gone because they went bankrupt. Walmart, Amazon and Costco are still here.

The datasheet for the PAM8610 IC is stamped on each page, "Not recommended for new designs". I guess Amazon UK sells old junk.
With a 12V supply, its maximum output into your 6 ohm speakers will be 8 Watts per channel at low distortion.
 

Buk

Member
The datasheet for the PAM8610 IC is stamped on each page, "Not recommended for new designs". I guess Amazon UK sells old junk.
I didn't know silicon chips had use by dates. Maybe Amazon UK are thrifty and pickle them to make the last longer?

I guess it depends where you get your datasheet; and that begs the question who labelled it such and why. Power Analog Microelectronics Inc no longer exist having been bought out by Diodes Inc. in late 2012; who then released their still current and nearly identically specified PAM 8620 in 2013. A case of the new broom sweeps clean I'd guess.

Upshot: A completely irrelevant attempt at a put down; that simply reenforces my charactrerisation of you as a child.

Interesting aside. Given that both PAM and Diodes do most of their design and manufacturing in Tiawan and Shanghai -- who would be manufacturing the Chinese copies you're so worried about?

Finally, perceived audio volume (Db) is a logarithmic scale meaning you need ~3 times the power to double the percieved volume, not 10x as you alluded to above. Just another peice of misinformation; hence my characterisation of you as a wannabe.
 

tomizett

Active Member
Finally, perceived audio volume (Db) is a logarithmic scale meaning you need ~3 times the power to double the percieved volume, not 10x as you alluded to above. Just another peice of misinformation; hence my characterisation of you as a wannabe.
For what it's worth, he's right on this one. It's a psychoacoustic thing, not just a physical one. It depends o what the stimulus is and how you measure it, but a lot of people use "10dB is twice as loud" as a rough rule of thumb.

Some members can be a little short, terse, impolite etc. We have some characters here; I try to encourage people not to be offended by them.
 

narkeleptk

Active Member
Interesting aside. Given that both PAM and Diodes do most of their design and manufacturing in Tiawan and Shanghai -- who would be manufacturing the Chinese copies you're so worried about?
The problem is not where its made, the problem is quality control. Copies are generally made with inferior material. Some designs are more copied then others so you would need to take more care when ordering them.
 

audioguru

Well-Known Member
Most Helpful Member
I do not bother about which company bought which company since the Oriental design of the PAM8610 has been replaced by the similar German (?) design of the PAM8620 that has "Power Limit with Non-Clip".

Siemens of Germany spun off its semiconductor division into Infinion Technologies of Germany.
American International Rectifier bought Oriental PAM.
Then Infinion bought International Rectifier.

Maybe the PAM8610 produced illegal radio interference?
Maybe the PAM8610 had a very bad problem when it produced clipping?
Then instead of trashing them, Amazon bought the trash and is selling it?
Oh, good point. Maybe the PAM8610 is no longer made but bad copies of it are sold by Amazon.
 

Latest threads

EE World Online Articles

Loading
Top