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crucialfix 25th September 2012 05:13 AM

Quick Question (TDA1562Q)
I am about to build my first amp. I will be using TDA1562Q with a 12v 3.4aH SLA battery.

I realize the battery fully charged will be around 14v which is recommened for the chip but I want to take into account long use and battery discharge.

Would using this:
DC 10-32V to 12-35V Step-up Boost Power Supply Module | eBay
to boost voltage to ~15 or 16v be an acceptable way to be able to run the amp longer without clipping?


Arty 25th September 2012 06:10 AM

nope, but a bigger battery will provide longer play time.
The conversion of energy is not for free, and a battery should not get under 10,5 or so volts, even if it is "discharged". If it does, you reduce its lifecycle.
Peukert's law - Wikipedia, the free encyclopedia
To get the best out of this amplifier 14.4 volts are not the best suited.
One should -if using a transformator and mains power- should tend to be closer to 16 volts, but no more than 17 volts. Even so, the capacitors must be upgraded to 25v ones, to avoid them from exploding.
BTW, this is a verry nice chip.

crucialfix 25th September 2012 06:25 AM

I realized I worded that wrong. I am not looking for longer battery life (3.4ah is largest that fits in my box), I am looking for longer time out of attenuation. So if the battery drops to 12v and bellow, the amp will still be getting 14v+ due to the step-up circuit.

In regards to your transformer/AC comment. Since this is my first amp I just wanted simplicity and smaller form factor. But if I do, should I find a circuit that converts 12vDC to 16vAC?

Arty 25th September 2012 09:44 AM

still no.
You will exhaust Your bateery faster.
The converter has its own losses, adding that to the amplifier's own losses.

crucialfix 25th September 2012 11:32 AM

Thank you, I understand now.

I was just trying to figure out how these are being powered:
thodio freedom hifi - the blog: thodio design 2 x 70 watts rms / 2 x 140 watts max TDA1562Q based amplifiers...

I see the SLA and he lists the TDA1562Q. I am just tryin to figure what is between the two or any other viable option available.

Arty 25th September 2012 06:16 PM

140 watt is not possible from this chip.
2x70 watt is possible, with utterly high distorsion at a single 14.4 volts.
One can try to push the IC to its limits with a well regulated powersupply set to 17 volts, but that requires a verry well regulated powersupply -to combat mains voltage riples- and verry big capacitor bank to make sure the rail voltage does not collapse under the load more than a few tenth of a volt.
in witch case its better to leave the class H chip region and go for units that have higher supply voltage handling ability.

at least, if you need more power.
an alternative and usualy better solution is to get better speakers that play louder from the same amount of power. -high sensitivity units-.
If it is a boombox then this solution might not be available.
But, maybe You should still consider it, as it is a good way to improve the battery life, and sound quality along with the maximum loudness at the cost of probably higher priced drivers.

btw, what speakers are you about to drive with this amplifier, and for how long / battery charge?

crucialfix 25th September 2012 09:46 PM

I am looking at the Polk Audio DB401 (45wRMS, 91dB) or the DB501 (45wRMS, 93dB). I am kind of limited to these because they are marine-certified which will fit my application.

I am still a little unsure on how to get 17 volts with a portability in mind.

I was also contemplating the LM3886 but have to still do a little more research on the dual supply.

Arty 25th September 2012 10:00 PM

those speakers are quite efficient.
You won't gona need the class H powermp to drive them , a less complicated tda 1557 will do just fine, probably overdrive them at 3/4 of full power.
I would shoot for the db501, higher sensitivity will be worth it.

The mentioned chip is a well known one with its sisters and borthers from car radio head units.
Taking into account that 90% of car speakers can't handle full power from a headunit, we can consider that the claimed 20 -ish watt -witch is actualy more closer to 15 before it starts to distort- is more than enough.
You will get quite a few hours of play time with reasonable loudness if you use
4,5V-os GP LAPOS ELEM, bliszteres kiszerelésben.
3 of these guys in seres to power a tda 1557q.
If you by the luck manage to have some rechargable battery then it will all be just fine.

so.. describe, what is the plan, and maybe you will see that battery power is at no way a problem :)

crucialfix 26th September 2012 05:33 PM

First of all, Arty, thank you for helping me through this.

That tda1557 seems interesting. Comparable to the TA2020, or any other tripath?

My plan is to have a boombox that can be able to play off the battery or alternatively being able to play while the battery is plugged in and charging.
It would be great to have an external volume control as well, but like I said, I am not wanting to complicate things if I dont have to.

Arty 26th September 2012 06:07 PM

are you kidding?
1557q is absolute up for the job.
the external volume controll is a cheapoo potmeter.
it is not like tripath chips, requires only few external components.
that is like 5 of them.
will run happily from 9 to 17 volts from anything you can find, but best options are:
small lead acid battery (UPS or bike battery will do perfectly)
2x9v NiMh battery + a diode.
I would vote for some small lead acid type of battery.
Will give you quite a few hours of play at full blast.
With just a few extra components "bass boost " can be done.

Car speakers are not the most documented types, but if You have managed to build the amplifier, there are options to mesure the T/S parameters of the speakers. Based on those a more o less proper box can be modelled to give acceptible accustic results, and with some additional circuitry even better results can be obtained.

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