Hello. For years i've been building little LM386 chip based amps powered by 6x NiMH AA 2000mAh batteries. I think i was using them with 8 ohm speakers. The amps were not particularly loud or great sounding, but the battery life was simply amazing. Considering the novelty of the amps (they are housed in little beer kegs), it was fine.
Recently i've been wanting to up the sound quality. I decided to try a 12v class D amp. I can't remember if i went with a Pam or TDA model. I powered it with 10x of the same NiMH batteries. The amp sounds much better, but the battery life is only something like 5 hours. For my purposes that just isn't going to cut it.
My electronics and amp knowledge is admittedly poor, and that's why i am coming to you folks for advice. What type of amp (class D, analog chip, solid state, whatever) would best suit me if my goal is a better sounding amp than the LM386 chip offers, but with a similarly long battery life? Also, does the speaker that i choose (ohms? magnet size?) a big factor in the battery life equation?
For a better understanding of the size of my project, here is a picture of the one i currently use in my kitchen:
Thank you in advance for any advice you can offer,
-Jack
Recently i've been wanting to up the sound quality. I decided to try a 12v class D amp. I can't remember if i went with a Pam or TDA model. I powered it with 10x of the same NiMH batteries. The amp sounds much better, but the battery life is only something like 5 hours. For my purposes that just isn't going to cut it.
My electronics and amp knowledge is admittedly poor, and that's why i am coming to you folks for advice. What type of amp (class D, analog chip, solid state, whatever) would best suit me if my goal is a better sounding amp than the LM386 chip offers, but with a similarly long battery life? Also, does the speaker that i choose (ohms? magnet size?) a big factor in the battery life equation?
For a better understanding of the size of my project, here is a picture of the one i currently use in my kitchen:
Thank you in advance for any advice you can offer,
-Jack
Seems rather surprising to me that a 12V classD amplifier only lasted 5hrs on a 2Ahr battery pack. That rather implies you were pulling an average of 400mA from it, or around 5W average power. Seems an extraordinary amount of power, care to share more details about the precise amp module you were using?
ClassD has much better operating efficiency than classB (the kind the LM386 is) so would normally be the best choice, but it does depend a lot on the kind of music and how loud you play it. The LM386's 4mA quiescent current is a lot more miserly than many classD amps so at quiet volumes the LM386 may well give a longer battery life.
ClassD has much better operating efficiency than classB (the kind the LM386 is) so would normally be the best choice, but it does depend a lot on the kind of music and how loud you play it. The LM386's 4mA quiescent current is a lot more miserly than many classD amps so at quiet volumes the LM386 may well give a longer battery life.
Abraxalito, thanks for the reply. I believe the amp i chose was a 15 watt per channel model using a TDA7297 chip. I only have 1 speaker in the amp though so i am only using 1 of the channels (the input gets mixed before it reaches the amp). The speaker is a Fusion "Encounter" 5.25" full range model. 4 ohms, 190w peak, 35w rated.
I will say that in both test runs, the amp was being used at louder than what i would consider normal usage. We were camping on a friends property and the listeners were quite spread out.
Someone suggested i try Li-Ion batteries. I do see that there are more pre-made charger options available than i'm able to find with NiMH. If you guys think my amp/speaker combo is OK... i may try that route.
I will say that in both test runs, the amp was being used at louder than what i would consider normal usage. We were camping on a friends property and the listeners were quite spread out.
Someone suggested i try Li-Ion batteries. I do see that there are more pre-made charger options available than i'm able to find with NiMH. If you guys think my amp/speaker combo is OK... i may try that route.
The amp being based on TDA7297 goes part way towards explaining your experience. Its not a classD chip, rather the usual classAB. Its quiescent current is quite low given its a stereo bridged chip (50mA typical). Using such a low impedance speaker (4ohm) on this chip definitely means efficiency's going to suffer greatly.
Lithium Ion batteries offer the highest energy density per kg and on Taobao charging modules for them cost next to nothing (assuming 5V USB input). I recently have started using 18650s in my projects which give about 10Whrs if you buy the Japanese (Panasonic) ones. Korean (Samsung) are cheaper but generally slightly lower capacity.
Lithium Ion batteries offer the highest energy density per kg and on Taobao charging modules for them cost next to nothing (assuming 5V USB input). I recently have started using 18650s in my projects which give about 10Whrs if you buy the Japanese (Panasonic) ones. Korean (Samsung) are cheaper but generally slightly lower capacity.
I'm running my TPA3116 on a 6 cell LiPo battery. I am using a 2.1 board which of course has two separate amp chips, one of which is bridged. At low volume it barely uses any power - around 1 Wh. My battery is a 3Ah at 22V so 66 Wh. The battery I'm using is a hobby drone battery, about $35USD.
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