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Crown MA12000i - Any Users Feedback

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ReubGold View Drop Down
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    Posted: 30 April 2019 at 12:47pm

Someone trying to flog one of these to a mate.

Don't know of anyone in Soundsystem world using it, do know ITECH 8 sounds good, but underpowered.

Is that same with this ?

Seems optimised for 4 ohm stereo, which is fine, but 20A power inlet, for amp that can draw 18A at 1/3 power pink noise, does not suggest specs are truthful.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2019 at 1:16pm
Specs are perfectly truthful, if you can read them properly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ReubGold Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2019 at 2:30pm
Originally posted by toastyghost toastyghost wrote:

Specs are perfectly truthful, if you can read them properly.


Would have thought, an amplifier capable of producing 4.5kwpc @ 4 ohms, would draw a little more than 18.7A doing it.

Have seen PL9, draw 22A, driving 2x cabs per channel at 4 ohms, and that is only rated at 3200wpc @ 4 ohms.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2019 at 3:46pm
So with 1/3rd power pink noise - presumably that means an input level sufficient to generate 33% of the rated output power continuously - and a 4r load per channel, it consumes 18.7A and generates 144.2 watts per amp at the output, or 2696.5 watts total. So not anything like 4.5kW. 
That's 1348 watts per channel. Multiply that by 3 to get the theoretical max continuous power, and you get 4045 watts per channel or 8090 watts for the whole amp.
But you'd never run it that hard unless you wanted to turn all your woofers to confetti. The 1/8th power figures are more relevant to real world use, I would hope....

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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2019 at 6:23pm
This is a Class D amplifier with PWM. It does not draw current straight from the wall on demand. Not only that but the ratings for current draw are clearly listed as 12dB crest factor.

Besides which, as stated, 1/3 power is typical of clipping with this type of crest factor material.

Edited by toastyghost - 30 April 2019 at 6:25pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2019 at 6:41pm
Believe me., you can burn coils with this one Embarrassed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris Grimshaw Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2019 at 9:30am
I've got one of these amps here. Excellent bit of kit. Sounds good in any frequency range, and a lot of power. I've hung 4x subs/side off mine and driven it hard. Give it a good mains supply and you'll be fine. If you run it 2ohm/ch off a generator with a 32A Ceeform output, it'll happily shut the generator down on the first kick. If you run it at the end of a couple of hundred metres of 32A Ceeform (with a big generator feeding a load of other stuff), the stage lights will dim with the bass.

With regards to the current draw thing, you're not interpreting the specs correctly. There's some maths coming, but hang in there.

First things first, let's talk about pink noise.
Pink noise is a random signal with equal energy per octave, and a 12dB crest factor. That means the peaks are 12dB above the RMS level. 12dB = 16x power.
Sine tones have 3dB crest factor, and square waves have 0dB. The latter can be easily seen - a square wave is, by definition, always at 100% output.

When you play pink noise through an amplifier and push the fader so that the clip lights are literally just about illuminating, your amplifier is not delivering continuous full power. It IS delivering full power at the peaks of the waveform, but the RMS power is still 12dB down.

ie, the clip lights are on because the amplifier is clipping the occasional peaks, but the long-term average power is at 1/16th of the theoretical maximum output.

1/8th power is often used because that's pink noise 3dB into clipping. Program material 3dB into clipping still sounds fairly acceptable - remember it's only the very peaks (kick, snare, maybe the loudest bits of vocals) that are suffering.
Since you've chopped the 12dB peaks down to 9dB, there's your 1/8th power figure.

Again, the amplifier is delivering 1/8th of it's available power, but the peak voltages are already clipping. If we swapped the pink noise for a sine tone of the same RMS power, we would be far away from clipping since sine tones have a very small crest factor.

Let's push the fader again. We were 3dB into clipping, but let's push the fader and make it 7dB into clip, so our crest factor is now 5dB. We're clipped the pink noise that heavily that it's approaching the crest factor of a sine wave.
In this situation (pink noise 7dB into clipping), the amplifier is delivering 1/3rd of it's available RMS power.

If you want the amplifier to deliver 100% power, you need to output square waves at full output. That's why the Crown datasheet is showing a couple of kilowatts output - that's the actual average power being delivered.
There isn't much program material that contains square waves at full output, mostly because it doesn't sound particularly musical. However, there's one track I can think of that gets close. When the bass drops, below 100Hz is a compressed sine wave with a 2dB crest factor. The fundamental is 36Hz.

Caustion - NSFW lyrics from the start: https://www.youtube.com/watch?v=UnQY3swM4tA

Where the usual pink noise test signal (9dB crest factor, a little into clipping) delivers 1/8th average power, this track is at 5/8ths. That's 5x the driver heating power for the same peak voltage, so be careful with the levels - your amplifier doesn't need to clip to burn out drivers.


Now that we can interpret the specs on the datasheet, it's up to the user to determine whether the amps will do what's needed.
FWIW, if I need a high-power 2-channel amplifier and have external DSP, the MA12000i is the first amp I reach for.

Chris
Quality sound from Sheffield
www.grimshawaudio.com
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