powering a 50 w amplifier by battery???

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
You provided 2 links. The ebay one is clearly fake, not 200W. Probably only about 2x15.
The other is OK, with 18V it gives you 2x 30 W, but consumes much more power than a ClassD, and needs a quite big heat sink.

Why you dropped TDA7492? It's better!

Old, not maintenanced SLA batteries are most often dead.
in fact 3 out of four were completely dead :(
a part from that i saw the data sheet of the tda7492 en basing on the diagrams i'll need at least 15V to achieve 10W power with a 4 ohm load, while I need at least 15-20 W rms ( yes, I've reduced my standards :) ) with 12 V DC...
looking for the right amplifier I'm litteraly going crazy... please help me :(...
 
I used a LiFePo4 battery from batteryspace.com for my 30 watt speaker. Its been working great! Gives about a 2 week average play time at 12.8v 6Ah. Not too heavy and more stable than most Li batteries. Also I used an amp from classdaudio.com 2x15watts in mono mode. It sounds good and does not run hot. Im sure there are less expensive options but I could not figure out what would be a good way to go. Most of the time I have experienced that cheap is always expensive. Hows the project going?
 
in fact 3 out of four were completely dead :(
a part from that i saw the data sheet of the tda7492 en basing on the diagrams i'll need at least 15V to achieve 10W power with a 4 ohm load, while I need at least 15-20 W rms ( yes, I've reduced my standards :) ) with 12 V DC...
looking for the right amplifier I'm litteraly going crazy... please help me :(...
With 12 V power supply basically all bridged amplifiers gives the same power to 4 ohm load, if they are capable to drive it. It is simple physics. More power requires more voltage, or less impedance.

There are some special chips with internal voltage boosters, but I dont remember the type. They are basically class AB, so not really efficient.
 
Pafi, I did not not notice an increase in power from adding more voltage to my system. Is it possible that it just pulls the extra power in amperage?

The answers is...Due to the logarithmic nature of human hearing, doubling the power delivered to the speaker will give a volume increase of 3dB - an increase in volume level that is just noticeable. To double the apparent volume level requires about ten times the power, which is equal to an increase of 10dB.

Mike
 
Last edited:
So then it's not just about voltage but the combo of amps with volts, watts.

No, it's "Due to the logarithmic nature of human hearing..." as I stated above. Doubling the power does not double the apparent volume increase, it only raises it by 3dB. In other words, going from 10 watts to 20 watts of available power output will only give a just noticeable loudness increase of 3dB. To DOUBLE the apparent volume level requires a 10dB increase, or TEN times the power on average.

Mike
 
Last edited:
I wish I could see and hear an example of this. I guess it's just going to take a few builds to get it fully. 10x power creates noticeable volume increase. 12v x 1a = 12watts. 12v x 10a = 120watts which would be 10x the first. Would this not create a noticeable volume increase without adding more voltage.
 
Moderator
Joined 2011
10x power creates noticeable volume increase. 12v x 1a = 12watts. 12v x 10a = 120watts
which would be 10x the first. Would this not create a noticeable volume increase without adding more voltage.

The supply's voltage and current capabilities only set a maximum limit to what the amplifier can do.
If you don't approach either of those limits in actual use, you won't notice a difference when increasing them.
In general, you'll reach one of the limits before the other, depending on the equipment. With larger capacity
batteries, you'll likely be voltage limited. With smaller batteries, probably current (and time) limited.
 
Last edited:
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.