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Class D Switching Power Amplifiers and Power D/A conversion

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Old 20th May 2012, 09:10 PM   #2811
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Quote:
Originally Posted by danielwritesbac View Post
Thick polyester/nylon/kevlar acoustic pad (or mesh) with the consistency of ScotchBrite scouring pads, don't retain water at all. No sheep were harmed.
Technically that's even worse as non-organic stuffing works as humidity condensers making you risk having standing water inside your speaker after consecutive days of use.

You have to remember the use conditions here. It's intended for use directly on the grass, during summer where daytime temperatures is easily 30 degrees and night time easily under 10 degrees. As humidity is always high near the ground/grass you get some very difficult circumstances the speaker has to work under.
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Old 21st May 2012, 05:05 PM   #2812
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Quote:
Originally Posted by Saturnus View Post
Technically that's even worse as non-organic stuffing works as humidity condensers making you risk having standing water inside your speaker after consecutive days of use.

You have to remember the use conditions here. It's intended for use directly on the grass, during summer where daytime temperatures is easily 30 degrees and night time easily under 10 degrees. As humidity is always high near the ground/grass you get some very difficult circumstances the speaker has to work under.
What are your thoughts on rough finish wood (for the inside) instead of slick finish wood?
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Old 21st May 2012, 05:18 PM   #2813
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What are your thoughts on rough finish wood (for the inside) instead of slick finish wood?
I certainly recommend sealing all exposed wood, both inside and outside. Remember one prototype I had with me a very rainy and damp festival where I hadn't even painted the plywood. The speaker was almost 1 kg heavier when I got home than what it was going there.
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Old 24th May 2012, 08:25 AM   #2814
kri5t is offline kri5t  Denmark
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Hello Saturnus

I am trying to build one of these for Roskilde this year. I have acquired the 12V batteries and the solar panels. Now I am looking for the amplifier and the speakers. My problem is that the 41hz amplifiers seems to be out of order and they don't know when it will get restocked. Can you recommend another amplifier to me?

(I am not experienced in soldering components onto a print board, so preferably I would like the amplifier to work out of the box)

Great guide by the way and I picked your design solely on the sustainable way it works with solar powered batteries. It is a very nice idea.

Thank you in advance
Kri5t
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Old 25th May 2012, 07:57 PM   #2815
Wubbaz is offline Wubbaz  Denmark
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Sorry if this has already been brought up, but does anyone know what type of DC male plug you insert into the preassembled AMP6B? I've tried with a few different types lying around my house, but I haven't been able to find one that fits yet.

And if you know what size of DC plug is needed, is there any chance someone also knows where I can buy that kind of plug? Preferably with a cable already mounted, or some really cheap adapter I can just remove after buying it.

Thanks a lot!
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Old 26th May 2012, 04:25 AM   #2816
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Originally Posted by kri5t View Post
. . .I have acquired the 12V batteries and the solar panels. Now I am looking for the amplifier . . . Great guide by the way and I picked your design solely on the sustainable way it works with solar powered batteries.. . .
If you can keep the voltage in between (min) 10v to 30v (max) then you could use this: Sure Electronics TK2050
How long does it take to remove up to 20v from the batteries? quite a while.

However, if you can keep the voltage in between (min) 8v to 13.7v (max) then you could use this: Sure Electronics TA2024
How long does it take to remove up to 5.7v from the batteries? not long. This little amp would be awesome except for that problem. I haven't tried using a buck adapter with it.

You see, it looks like the smaller amplifier would be more efficient, and while that is surely true, the voltage range is far shorter and thus the playback time will be shorter with the smaller amplifier. For this reason, it seems that varieties of TK2050 (wide voltage range) are fairly popular for boominators.

Anything efficient and also with a wide voltage range will do for amplifier.
But, most important for battery operation is wide voltage range tolerance.

P.S.
Speaker load also affects efficiency:
4 ohm speakers, most heat, least play time (TA2040 does 16w)
8 ohm speakers, medium heat, medium play time
16 ohm speakers, least heat, most play time. (TK2050 does 25w)
So, the smaller amplifier might not be the most efficient after all--that depends on your application.
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Last edited by danielwritesbac; 26th May 2012 at 04:30 AM.
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Old 26th May 2012, 06:22 AM   #2817
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The TA2020 (or TA2021 and TA2024) are far more efficient than a TK2050. One of the reasons is the far lower quiescent current, basically meaning power not directly used for output but for other functions.

The TA2020 typically uses less power at full volume than a TK2050 uses in idle when supplied with the same voltage.

Therefore the TA2020 is always more efficient than a TK2050.
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Old 26th May 2012, 08:13 AM   #2818
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To expand on the above.

The typical operating voltages are assumed to be 12V and 24V respectively. The Boominator is a 4 ohm load. The TP2050 output chip in the TK2050 cannot drive 4 ohms loads at 24V unless it's paralleled. The TC200 controller in the TK2050 needs a voltage regular to supply it with +5V. We also assume a crest factor of 10dB (or 10%) when we estimate full volume power usage, ie. the delta between peak and average level in the music signal.

At 12V and idle, stereo

TA2020: 60mA x 12V = 0.7W
TK2050: (95mA* x 12V) + (125mA x 2 x 12V) = 4.1W

At 12V and full stereo volume (music output)

TA2020: (60mA x 12V) + (12^2 / 4 x 10%) = 4.3W (88% efficiency)
TK2050: (60mA x 1.5* x 12V) + (125mA x 2 x 12V) + (12^2 / 4 x 10%) = 7.7W (79% efficiency)

At 24V and idle, stereo

TK2050: (115mA** x 24V) + (125mA x 2 x 24V) = 8.8W

At 24V and full stereo volume (music output)

TK2050: (115mA** x 24V) + (125mA x 2 x 24V) + (24^2 / 4 x 10%) = 23.2W (84% efficiency)

* 95mA includes voltage regulator power loss
** 115mA includes voltage regulator power loss

Ok, I admit my mistake above, so a TK2050 does not use more power in idle at 12V than TA2020 at full volume but it's close to the same 4.1W vs. 4.3W.

Last edited by Saturnus; 26th May 2012 at 08:19 AM.
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Old 26th May 2012, 03:46 PM   #2819
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Interesting comparison. SO, what do you think of this TA2021: FEIXIANG252B TA2021B 25W+25W Amplifier-EF2 ?
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Old 27th May 2012, 12:12 PM   #2820
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I've just started to make my own paper schematics before I start building my boomi and I realized that the holes in Saturnus schematics for the HP 10W is 220 mm in diameter, but the HP 10W that I have is actually 260 mm from edge to edge and measured inside the rim they're 236 mm.
This feels weird to me, I think it must affect the sound? Shouldn't the hole in the cabinet be as large as the cone at least? Perhaps the design of the HP 10W has changed again...
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