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Vince
Dodge Dakota
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7/10/2002
14:04:47
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 Subject: Different volt ratings (VDC) on amps?
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Can anyone shed some light on the different voltage ratings that affect the Watts that amplifiers put out. I've heard that 14.4 VDC is pretty normal when the engine is running, where 12.5 is normal when the engine is off. Anything additional will greatly help.
Thanks,
Vince
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R/Truck
Dodge Dakota
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7/10/2002
15:37:34
|  RE: Different volt ratings (VDC) on amps?
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Good news: unregulated amps can actually produce more watts with higher voltage.
Bad news: you can't really tell the difference, the spl difference is something like 1-2 dB
Regulated amps will produce the same amount of watts within a certain amount of volts. example: 11-14.4 volts = 100 watts solid, no matter if the car is on or off
The regulated amps tend to take up more power (amps) since the may have to produce more watts with less volts.
But it really doesn't matter either way, since it so hard to hear the extra watts. So don't let this be a major part of your decision when buying an amp.
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Vince
Dodge Dakota
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7/10/2002
19:21:28
| RE: Different volt ratings (VDC) on amps?
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Thanks for the input. The only example I have where this seems hard to believe (about very little difference), is the MTX Thunder 6304. It boasts a meager 37.5W x 4-channels at 12.5 VDC. Take it up to 14.4 VDC, and it jumps to 90W x 4. Now that's quite a jump. Are you saying that I wouldn't really notice a difference?
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Waltherone
Dodge Dakota
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7/10/2002
22:42:21
| RE: Different volt ratings (VDC) on amps?
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Every time you double your power, you gain a theoretical 3dB. And, 3dB sounds twice as loud (93 dB sounds twice as loud as 90dB volume)
As R/Truck said tho, with just a couple hundred watts difference, you're lookin at about a 1dB difference. I have a test tone around here somewhere that plays at a certain level for a few seconds, then increases by 1dB. You can hear it, very very faintly, but this is a test tone mind you, in music where things aren't all the same volume anyway, won't make a bit of difference.
As for the 37W vs 90 thing, make sure that 90 isn't also at 2ohm. No amp is going to put out more than double even with 100% effeciency.
Power is simply voltage times current. Like, an amp drawin 50 amps of power, will make, at 12V, about 600 watts. That is of course assuming 100% effeciency, which no amp on the market can claim yet (most class d's only boast about 70% effeciency) So, with this in mind, it's obvious with just a small math equation that by simply boosting the voltage by 2 volts, the power simply canNOT double. It's literally impossible, by the laws of physics, unless that amp for some reason started drawing a lot more current when they switched to 14V
A jump from 37-90W would be an audible difference, because its more than double the power (would be audible on midrange and up, not so much on bass because that little power wouldn't create much bass anyway, since bass takes a lot of power to produce)but like said above, yeah, 2volts will not make the amp's power double. Most likely that 90 was at 2ohm, in which case its quite normal for the power to double..
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waltherone
Dodge Dakota
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7/10/2002
22:46:31
| RE: Different volt ratings (VDC) on amps?
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And also I just checked the specs on the 6304, it does 75W at 2ohm at 12V, so that 90W was almost certainly at 2ohm at 14V, in which case the lower impedence is what made the big power increase, not the voltage.
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R/Truck
Dodge Dakota
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7/11/2002
10:38:04
| RE: Different volt ratings (VDC) on amps?
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One thing about MTX is that they under rate their specs by a lot. There amps usuelly produce twice the amount of power that they claim. Look at how many fuses they have on the amp compared to another one with the same watts. Their amps also come with a test report card, and it shows what the amp actually produces with certain voltage and THD. I have a 6500D and it was rated at 250 watts at 4ohm, but the card actually showed something like 400 watts and even more with 14.4 volts. You won't be dissappointed with that amp.
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Vince
Dodge Dakota
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7/11/2002
11:22:03
| RE: Different volt ratings (VDC) on amps?
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Thank you very much for your replies. I believe what you are saying about the 90 Watts. That being the case, MTX must have made an error on their own description on their website for the 6304. Just in case you want to see what I'm talking about, go into www.MTX.com, under amps, then "Compare 4-channel amps." They say that at 14.4V, it puts out 90 x 4 at 4 ohms. It says 165x4 at 2 Ohms. At 12.5V, it says 37.5x4 at 4 Ohms. That's what confused me so much. Maybe they underrated the 37.5x4 at 12.5V, and were more accurate with the 90x4 at 14.4V. I don't really know, but thank you very much for the discussion. I'm about 98% sure I'm going for the 6304.
Vince
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R/Truck
Dodge Dakota
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7/11/2002
16:27:31
| RE: Different volt ratings (VDC) on amps?
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Don't worry about the watts, the MTX is a very clean (110dB S/N) and powerful amp. It will pound any speaker you throw at it, plus the amps are bullit proof in the heat. Go for it.
Plus all the watts they show you are way under what it really produces. Just take a look at it's test card inside the box.
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JMII
Dodge Dakota
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7/11/2002
20:17:40
|  RE: Different volt ratings (VDC) on amps?
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Good info above... I'll just add that the 14.4 V is old "trick" used by those cheap amp makers (not MTX) to "boost" their amp ratings. These are the same companies that claim their amps put out 400 watts when they only have 20 amp fuse in them (20a X 14.4v = 288w only, so it's impossible).
Another thing to keep in mind... if you actually check the voltage at your amp while playing music you might be surprized by how low it gets :o 12.5 is more realistic of a number . However like everyone said above, chances are you'll never hear the difference anyway, especially with a powerful amp in a 2ohm load.
BTW I run HiFonics amps which are regulated - it's just the way the manufacture designs the amp.
- John
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