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Class D Switching Power Amplifiers and Power D/A conversion

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Old 14th January 2009, 12:48 AM   #241
MartinQ is offline MartinQ  Canada
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Quote:
Originally posted by Saturnus
Also understand that going from 12V to 24V, you'll need 4 batteries in series/parallel on 24V to have the same battery life as a 12V setup has on one battery.
Is this because the module is much less efficient with a 24V supply than with a 12V? You're suggesting the efficiency drops in half with a doubling of the supply?
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Old 14th January 2009, 01:28 AM   #242
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Quote:
Originally posted by MartinQ


Is this because the module is much less efficient with a 24V supply than with a 12V? You're suggesting the efficiency drops in half with a doubling of the supply?
No, it's because output power quadruples.
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Old 14th January 2009, 07:38 AM   #243
v-bro is offline v-bro  Netherlands
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I'd start with an AMP9-B and then perhaps another one paralleled on the subs later on (if indeed you still want that after you've tried it with a single unit)

On the other hand when 12V is what you're gonna end up with after all you would be better off with just one or two AMP6-B. It would result in the same output power, but less consumption at idle....
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Old 14th January 2009, 09:51 AM   #244
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perhaps I should have stated my reasons for running 24v,

I think for this application I'd be happy with 2 - 3 hrs of battery life, without any 'extra' charging.. (i plan to make a bicycle powered charger)

Also, given that the system is designed to be run with: Click the image to open in full size.
(the above photo is does not show the finished design where the mixer will be fully incorporated into the top surface of the wheelbarrow)


Which in itself will require 3A at 24v for the inverter to run turntables + mixer. (this figure includes (in)efficiency of the inverter. (the inverter is 24v)

If I intended to use this type of batter.

I would I calculate expected battery life? If I assumed another 3A at 24v for amplifier current draw? ~ (total 6A) should yield at least 2hr lifetime?
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Old 14th January 2009, 10:30 AM   #245
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It's highly doubtful that you'll need the full 3A to the inverter. Or that you even need the inverters in the first place. The 1200MKII's use between 180mA and 300mA on a internal 18V DC supply depending on pitch. I can't see what particular mxer you have but my friend has a similar one which we modified to run on DC as well. It uses about 400mA maximum on the same 18V supply (the internal supply is 15V over a voltage regulator so we just plugged the 18V line in before the voltage regulator instead of after as on the 1200MKII's as variation in supply voltage doesn't matter on the 1200MKII because of it's motor controller)

The whole setup thus uses about 1A directly on 18V for which we connected 3 6V 12Ah batteries in series (same size and type as the 12V 7Ah batteries I use in the Boominator just a little more expensive). That gives him about 10 hours of runtime on the turntable setup.

As an interesting experiment you could even run the whole setup on 18V including the amp9basic. 18V on the amp9basic would double the output power compared to 12V but would be half compared to 24V. And is actually a very good compromise.
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Old 14th January 2009, 12:59 PM   #246
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my original plan was to convert a mixer and turntables to run from a dc/battery source.

The mixer that I have is an Ecler Nuo2.? I'll open up a 1210 to see If I can see what you are talking about. I would prefer not to use an inverter..

the 12AH 6v batteries are about 10 each... 6 of these working out 20 cheaper than 4 12v ones. 18v is looking to be a reasonable option. Compact to!
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Old 16th January 2009, 11:57 AM   #247
v-bro is offline v-bro  Netherlands
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Quote:
Originally posted by col


V-bro That would be awesome! There are a couple of us using the NTE-1 to balance up connections with the Tripath/41hz amps over here now. It's a must connecting to pro-audio gear.

col.

Well I did the measurements!

The NTE-1 needs an 1,6Kohm resistor and 470nF (0,47uF) cap as a correction network.

I have used a 47Kohm input impedance, but this didn't make a dramatic difference, the circuit is generally usable on any type of input.

Here's how it's done:
Attached Images
File Type: jpg nte-1 correction.jpg (7.7 KB, 966 views)
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Old 16th January 2009, 10:06 PM   #248
col is offline col  Australia
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Hi V-bro, thanks for that. I will adjust my NTE-1s on my amp9b.

regards,
col.
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Old 20th January 2009, 10:07 AM   #249
tfan is offline tfan  Denmark
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Hi Saturnus,

I've been the guy taking care of building the stereo for my camp since Roskilde 2007.

I've been using existing speaker designs, but also experimenting with building my own boxes, which was a big failure, as I soon came to realize that it's not just about putting speakers into a box and making a hole for the bass I guess you learn from your mistakes.
(From before we painted it black, I'm not proud of it: http://www.youtube.com/watch?v=LQu7Cb-K9oE)

I need a bit more power than you for my system, as I'm putting an Eee pc into mine (it only consumes 12V/~2.5A). I was thinking how I could solve my "enormous" need for more power for some time, as car batteries are pretty expensive over here, until I came across a place(autoophugger) offering used, but fully functional car batteries for 1/6 of the original price.

My goal each year is to improve it somehow. ... well, the design from last year didn't work at all, so the whole thing is going to be rebuild. The only thing I'm going to keep is the car radio (to be able to play cd's) and the batteries from past years.

My stereo is known for being mobile. We had some great random parties from going down to the booths to buy more beer and wine I want to keep it that way, so I'm going to make it even easy to come around with, by building it into a bike trailer.

The sound was really bad last year, because of my stupid design. From reading your thread, I've realized that I don't need that much volume for the drivers at all, I just need to build it right with the right driver for my amplifier. I'll maybe be a copycat and steal your magnet-to-magnet bass-reflex design, if I have enough money for 4 drivers

The reason why I'm writing here was not to write a novel The only danish site I could find selling the HP10W, took more than twice the price compared to the German company, somebody linked to in this thread. I actually just wanted to hear if somebody would mind to have at look at this: http://www.dlt.dk/Products/productin...tID=ZO%20P1040

Can this driver match the HP10W? I know I primarily have to look for sensitivity, but I just want to be sure so I don't waste my money



Thanks,

Thomas
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Old 20th January 2009, 11:44 AM   #250
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Try and measure the power consumption of the head unit before deciding to keep it as part of the system. In one of my earlier versions I had a standard low cost head unit for a year until I found out that a 55Ah car battery will only have enough juice for about 1-2 days.

That's because, a) a car battery is not as good a source as SLAs when drained continously as they're designed to supply high peak current instead and rely on the cars alternator to supply the continous power demand in the car so you should only count on about 60% of a car battery's rated amp hours to be available, and b) a car head unit has surprisingly high idle current, I measured 18 watt draw in idle on mine with about 27 watts average under load and that's not acceptable.

A solution is to have a discman to keep having the choice of playing CDs, just do like on mine where you can switch between different sources by plugging the headphone output of your source into it. That way you can play on anybody's iPod or tiny boombox.

From reviews on several sites the Eee PC draw a peak of 18 watts with an average of just under 15 watts but I guess during recharging it would draw more.

I actually considered the Zomax P1040 for the Boominator, so much so that I bought 2 to test them against the P.Audio HP10W's. The HP10W's won out for several reasons, a) the Vas and Qts of the P1040's dictate a larger cabinet than the HP10W's, b) the physical dimensions of the P1040's would not suit the magnet to magnet construction, c) the weigh slightly more but with 4 drivers that adds up to 2 extra kilos and d) the sound quality of the HP10W's was better with far better detail in midrange. The only significant advantage of the P1040s was a 1db better measured sensitivity.

My recommendations: make an exact copy of the Boominator! With or without the solar panels

While that's hardly original, it's a fully functional design and you can just add personal details/bling in painting it in interesting colours, have PA metal corners, build in a LED lightshow etc etc.

Then make a seperate box for the Eee PC and the batteries needed to power it. In that box you could keep the mp3 players, discman, all chargers and wires.
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