Adapting a pair speakers salvaged from a defunct TV

[Buk]

since the Oriental design of the PAM8610 has been replaced by the similar German (?) design of the PAM8620

And there you go just making **** up.

Maybe...?
Maybe...?
Then ...?

Turning your paranoid, Sinophobic rants into questions doesn't engender them any less childish.

Maybe ... you should consider consulting a psychiatrist about your fears.

Reality is: in China -- just as in Canada, USA, UK, Germany and every other country on earth -- some small percentage of people and companies are dishonest.

 

[audioguru]

The original PAM8610 datasheet by PAM company is dated 2008.
The new datasheet for the PAM8610 by Diodes Inc. is dated 9 months ago and says, "Not recommended for new designs". Digikey has many in stock.
The improved PAM8620 datasheet by Diodes Inc. is dated 2013. Digikey has none in stock.

Many Chinese module manufacturers sell a PAM8620 amplifier module including Amazon so buy one. You might be lucky to get one that works.

 

[Buk]

so buy one

Are you giving me your permission?
Or issuing a command?

Either way, it does not matter as nothing you say is of any consequence as you have demonstrated that nothing you say can be trusted to not be either made up; coloured by your personal biases; or both.

I see now how you got your 'most helpful member' accolade; you just keep on posting crap in eveyr new thread. Never mind the quality; feel the width.

 

[rjenkinsgb]

Just ignore AG, he does tend to sound like a broken record.

It appears the PAM series ICs are just about all there is for high efficiency amplifiers 5V operation. There are many sellers on amazon & ebay etc. [Correction - see below].

For the cost, it may be worth trying one to see of it works OK and the quality & volume are acceptable; theoretically you could get near 1W per speaker, which should be OK for desktop use.
The amp modules are very cheap it's a simple experiment to do a lashup test, and the only real way to really know if one is suitable for your needs.


I've built an amp for my PC but using higher power amp modules based on the TPA3116 D2 IC; I've used quite a few different amp modules containing those, from ebay, and never had any problems. Some run my whole-house audio system.
You do need a separate power supply if you use these, though; 12V or higher (up to 24V.) [No, again see below].

These are examples of common boards I've got; there are loads, from numerous suppliers.

Pardon our interruption...

4.5V-27V TPA3116 D2 50W+50W Dual Channel Digital Power Amplifier 50Wx2 Stereo UK | eBay

Output Power: 50Wx2. Channels: Two Channel Stereo. Power reverse protection. Large area copper coating.

www.ebay.co.uk

(I have three of the first style in the PC amp, plus a separate surround audio control PCB; a bank of the second style are in the house audio, after modding to directly access the balanced input on the amp IC).

The second one claims to work down to under 5V; I never noticed that before, but I was not looking for low voltage ones.

I've just tried a spare module at 5V from a little test rig regulator, and it is surprisingly good - enough volume to be annoyingly loud with speakers close to you, I've not got it near full for a comfortable level.
The little reg board uses linear regulators and has a 12V supply in to it, so at half an amp it would be dissipating around 3.5W of heat (and rather warm). It is staying stone cold, so the amp operating current is quite low.

The only small speakers I have to hand are a couple of tiny bare ones ripped from some scrapped cheap PC speakers years ago; it's a bit tinny like this, too much treble & not enough bass - but I think it would be fine with the speaker in suitable enclosures.

(The old minidisc player was the only thing I could think of to get a 3.5mm audio source next to the other parts).

It's good enough to leave on for background music while continuing to type !
[The MD player had the Deep Purple "Under The Gun" album in it when I dug it out].

 

[Buk]

Thank you for doing this. Above and beyond.

I was never fixated on the USB idea, it just seemed like a convenient source of power. Having gotten used to the USB plugs on some smartphone fast chargers delivering 10W or 15W of power and having read somewhere --without taking any particular note -- that USB 3.x had substantially increased the specified power availability over USB 2.0, it seems it might work for this. Especially as my old monitor had 2W/channel built-in and I rarely needed to turn them >50%.

I've ordered the PAM 8610 board I linked above -- I like the idea of the class D design. I'll try it with the USB 3.1 sourced from the PC back panel and see if the ~4W output suffices.

If not, I've a few DC adapters I can try: 5VDC@2A; 15VDC@200mA; 12VDC@4A. Once I've settled on what I need I'll probably look to buying a dedicated board and wrapping the whole lot up in some sort of enclosure.

The speakers are self contained base reflex units, so the box doesn't need to be anything fancy or complicated.

 

[Nigel Goodwin]

Thank you for doing this. Above and beyond.

I was never fixated on the USB idea, it just seemed like a convenient source of power. Having gotten used to the USB plugs on some smartphone fast chargers delivering 10W or 15W of power and having read somewhere --without taking any particular note -- that USB 3.x had substantially increased the specified power availability over USB 2.0, it seems it might work for this. Especially as my old monitor had 2W/channel built-in and I rarely needed to turn them >50%.

I've ordered the PAM 8610 board I linked above -- I like the idea of the class D design. I'll try it with the USB 3.1 sourced from the PC back panel and see if the ~4W output suffices.

If not, I've a few DC adapters I can try: 5VDC@2A; 15VDC@200mA; 12VDC@4A. Once I've settled on what I need I'll probably look to buying a dedicated board and wrapping the whole lot up in some sort of enclosure.

The speakers are self contained base reflex units, so the box doesn't need to be anything fancy or complicated.

A LOT depends how efficient the speakers are, and how much bass they give (little as it might be) - in order to improve the bass the speakers efficiency is reduced. The amplifiers in the TV certainly won't be fed off 5V, more likely 24V or so - and the power available at 5V doesn't matter much anyway, as 5V is too low a voltage to give any degree of power to loudspeakers.

Basically, if you have 4 ohm speakers you can get 4W from a 12V supply, or 16W from a 24V supply - with 8 ohms you get half power.

 

[Buk]

Please don't take anything I say as a statement of fact; it is just my -- possibly incorrect -- logic based on limited knowledge. Please correct my errors.

The speakers I have are labelled as 10W/6Ω, have 3 speakers each and look like this:
:

I assume that they use passive crossover, but as they are welded units, there is no way to look inside without ruinning them. They have reflex output holes on the bottom:

According to my elementary understanding, if you feed 5V into 6Ω; I=5v/6Ω = 5/6; W = 5*5/6 = 25/6= 4.166W.

The amp claim 90% efficiency, so 4.1667*0.9 = 3.75 to the speakers and say 50% sound and 50% heat, a bit under 2W of audio per channel. which is all I had from my old monitors built-in speakers and it was perfectly adequate for my simple needs.

If I use 12V in to 6Ω, I get I=12/6 = 2* 12 = 24W * 0.9 * 0.5 = 10.8 W output/channel which is more than I need, but I think (assume) that the extra headroom will serve to minimise distortion at the low levels of volume I need.

 

[Nigel Goodwin]

Please don't take anything I say as a statement of fact; it is just my -- possibly incorrect -- logic based on limited knowledge. Please correct my errors.

The speakers I have are labelled as 10W/6Ω, have 3 speakers each and look like this:
:View attachment 131919
View attachment 131920
I assume that they use passive crossover, but as they are welded units, there is no way to look inside without ruinning them. They have reflex output holes on the bottom:
View attachment 131921
According to my elementary understanding, if you feed 5V into 6Ω; I=5v/6Ω = 5/6; W = 5*5/6 = 25/6= 4.166W.

The amp claim 90% efficiency, so 4.1667*0.9 = 3.75 to the speakers and say 50% sound and 50% heat, a bit under 2W of audio per channel. which is all I had from my old monitors built-in speakers and it was perfectly adequate for my simple needs.

If I use 12V in to 6Ω, I get I=12/6 = 2* 12 = 24W * 0.9 * 0.5 = 10.8 W output/channel which is more than I need, but I think (assume) that the extra headroom will serve to minimise distortion at the low levels of volume I need.

Your entire premise is wrong I'm afraid - you're confusing resistance and impedance, and DC and AC.

The speakers also don't seem to be 6 ohm (impedance), as you measured them as 8 ohm (resistance) - generally (and in the many of hundreds I've measured over the years) an 8 ohm speaker reads around 6 ohms resistance, and a 4 ohm one around 3 ohms - basically DC resistance (with a meter) is normally about 3/4 of the impedance. Impedance is a funny thing anyway, and isn't far off a 'guess' as it varies by frequency.

With a 5V supply the maximum AC output voltage can only be 5V p-p (peak to peak), this calculates as only 1.77V RMS, which gives about 0.5W to a 6 ohm speaker. Assuming the amplifier is bridged, this effectively gives twice the voltage, increasing power to 2W. This assumes zero losses, and you obviously won't get 5V p-p off a 5V supply, there are always losses, and double the losses if using a bridged amplifier.

 

[Buk]

The speakers also don't seem to be 6 ohm (impedance), as you measured them as 8 ohm (resistance) - generally (and in the many of hundreds I've measured over the years) an 8 ohm speaker reads around 6 ohms resistance, and a 4 ohm one around 3 ohms - basically DC resistance (with a meter) is normally about 3/4 of the impedance.

Hm. That puzzled me. I cannot see why speakers built by or for a TV manufacturer for installation in their TVs, would be incorrectly labelled.

So I dug out the clamp meter I use for household stuff, put new batteries in and tested again. This time I get a reading of 5 ohms. (This meter doesn't do decimal places.) Then I checked the 9V battery in my multimeter and it flickers between 4v and 5v. Ie. its dead! I don't have a replacement to hand.

I also suspect that there are some passive components inside, as the resistance drops slowly after the initial connection from ~8 down to 5ohms over a couple of seconds.

 

[Nigel Goodwin]

Hm. That puzzled me. I cannot see why speakers built by or for a TV manufacturer for installation in their TVs, would be incorrectly labelled.

Like I said, you can't measure them using a meter, as that just measures DC resistance, and in fact you can't measure them accurately anyway as there's no accurate value possible - the specified figure is just a rough estimate.

But no one wants the figure on the speaker to read "varies between 3 ohms and 67.5 ohms".

 

[audioguru]

The datasheet for the PAM8610 amplifier IC says the minimum supply is 7V. If you use a 12V supply then the amplifier will produce 10W per stereo channel into your 6 ohm speakers at fairly low distortion.

 

[Buk]

Like I said, you can't measure them using a meter, as that just measures DC resistance,

Understood, but my confusion was why my resistance reading was greater than the marked impedance rather than less as you -- and other sources -- pointed out it should be. The low battery explained it.

 

[Nigel Goodwin]

Understood, but my confusion was why my resistance reading was greater than the marked impedance rather than less as you -- and other sources -- pointed out it should be. The low battery explained it.

Funny things happen as batteries get too low, you'd think meters would have a warning that it was happening, but most don't seem to.

 

[Buk]

In case anyone is interested. It lives:

And the verdict is good, the base on the Blondie track at half volume made the keys on my keyboard rattle; and the clarity of the crystal notes on this video

frankly astonished me. (Not a a HiFI buff!)

It is a little noisy as is when nothing is playing -- but this room is full of emi, Hopefully it'll improve once I get it into a grounded enclosure of some kind. For now, I'll dig out some switches and connect up the mute & off buttons.

Thanks for the help guys.

 

[audioguru]

Thanks, i saved the crystal Glasses music and found this guitar video playing the difference between soft clipping diode location and hard clipping location: