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Class D Switching Power Amplifiers and Power D/A conversion

Class D amp - battery as PSU
Class D amp - battery as PSU
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Old 8th January 2020, 09:40 PM   #21
Turbowatch2 is offline Turbowatch2  Germany
diyAudio Member
Join Date: Aug 2013
Location: Northern germany
Chemical energy is to slow for audio. Any well sounding battery powered amp has additional, huge capacitor storage, more than a transformer/ mains driven one would have or it will sound weak and lifeless. The idea is nice, but it does not work for sound quality.
Battery powered amp, pre.amp, DAC, CD -player, all has been done,many times and did not have the desired effect.
So if even a cheap SMPS instead of expensive, complicated battery cells, connected to the same power supply, sounds better, what is the value?
There are some good pre-amps with battery power (lead, Nicad and NiMh) out there, but regular powered ones are always better. Has been tried again and again, starting decades ago. No new idea...
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Old 9th January 2020, 02:46 AM   #22
Impishbynature is offline Impishbynature  Australia
diyAudio Member
Join Date: Jan 2020

I would like to understand in a slightly more formal or measured way how this belief exists.

Basically, first thing as I see it is if you rely on capacitors to support a switch mode, the same amount of capacitiance will acheive the same result on a battery, unless the sag on the battery is slower than the time constant of the attached capacitance (to the level of volt drop decreed aceeptable). A lithium battery is plenty fast compared to some 10's of thousands of uF.

From my industrially deaf ears, I only hear better sound from battery powered class D amps I have used vs SMPS, no power supply noise at all is the first thing.

Please feel free to go into as much technical detail is needed, I am an electrical engineer specialising in industrial design and would like to understand if I am missing something.

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Old 11th January 2020, 11:40 PM   #23
Turbowatch2 is offline Turbowatch2  Germany
diyAudio Member
Join Date: Aug 2013
Location: Northern germany
All you miss is 40 years of HIFI development. Battery driven high end has been tried a thousand times, but never worked audible better than "usual" stuff.

You are free to build whatever you believe is best for you. If it sounds better to your ears, fine. If it makes you feel happy, perfect.
Nothing is easier than connecting a bunch of LiPo chunks or what ever is your favorite.

Good luck!
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Old 12th January 2020, 12:56 AM   #24
impuls60 is offline impuls60  Norway
diyAudio Member
Join Date: Apr 2011
Some old laptop batteries (18650) can struggle with 5-7 ampere. Make sure to find the spec through the series number on cells or battery casing. I bough some new Samsung batteries that couldnt handle 7A. There is night and day difference between 18650s. I've tried running 5 18650 in series with a tpa3116 and it worked fine until the end were voltage drop became noticable as less bass.
I dont think this solution will play better than a regular good psu if you dont use new high current batteries. It will just be decent since the esr of a single row of used batteries will be high. The risk is going up by a lot with older cells! If one fails down to 1-2V you will overcharge that cell and all that energy will heat up that failed cell. In all professional eboards there is a temp fuses to keep cells from blowing up. And battery packs in eboards fails quite often. A bms is a cheap solution and needed because of the relative high charge rate you plan to use.
Impishbynature, a good 18650 battery has the same ability as a huge capacitance and very low esr vs supercapasitor. I tried to build a booster psu for an rc car once. I learned that 4.2V stepped up to 11.1v and a lot of capacitance wasn't in the same league as a tiny lipo battery for buffering the 11.1V before going into the speedcontroller. Supercaps must be 10x better to compare to a lipo of similiar weight. Thats why no one uses supercaps in cars..
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