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American Legacy Amplifiers


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Velocity Motors 
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Joined: March 08, 2002
Location: Manitoba, Canada
Posted: June 04, 2002 at 10:11 AM / IP Logged  

Here is part of an article that explains S/N ratio:

S/N ratio (Signal to Noise ratio). This is a number, measured in decibels which compares the noise inherent to a component, to that of the signal that is passed through the unit. Let's look at something like an good quality equalizer versus a much lesser quality unit. Lets compare the Zapco EQ30-SL with the Clarion EQ-74. Both units are graphic equalizers. The Zapco unit has a S/N ratio listed at >110 dB for which we will refer to it as 110 dB, and the clarion unit is listed at 100 dB.

If you are not familiar with the Decibel scale, it was created and put into use by Alexander Graham Bell to help describe the large ratios of sounds with respect to intensity. a decibel, which is one tenth of a bel is considered to be the smallest perceivable change in sound at the human ears most sensitive frequency. a change of 3dB is audible at almost all frequencies.
The decibel scale scale can also be used to describe ratios of large numbers. Something that is 3 db more than something else is actually twice that of the opriginal in level. So, a voltage of 2 volts is 3 dB more than that of one volt. A voltage of 2000 volts, is also 3dB more than 1000 volts. This is a logarithmic scale that deals with ratios.
A unit with a signal to noise ratio of 110dB is one that will invoke a noise component into the system that is 110dB quieter or smaller than the signal itself. Between the two units we have a difference of 10dB, this equates to a difference of 10 times.
To clarify, the Zapco unit has a noise level which is 110dB or 1x10^11 times smaller than that of the signal. If the max signal is 8 volts, then the maximum noise voltage is 1 Quadrillionth of that. Sure this is small, but it adds up quickly. A head unit, equalizer, crossover and amplifier all have noise, and it adds as it goes down the chain. It also gets amplified, so it can be heard.

As for the other question, remember that when you are on the other side of the decimal place, the larger the number , the smaller the value. So for instance, .04 %  is larger in value than .008 % . I hope this makes sense.

Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
hadji_85 
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Joined: May 28, 2002
Location: United States
Posted: June 04, 2002 at 12:51 PM / IP Logged  
ah crap, i'm glad i'm not taking calc in highschool ....
~Hadji
hadji_85 
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Posted: June 04, 2002 at 12:52 PM / IP Logged  
i hope my teachers never see this
~Hadji
hot_shot_guy123 
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Joined: March 09, 2002
Location: Canada
Posted: June 04, 2002 at 3:09 PM / IP Logged  

Thanks Velocity, I always wondered about this same topic and you answered it.  So,

.04 = no good, .008 = better

"Light travels faster then sound, that's why some people seem bright until you hear them speak."
hot_shot_guy123
Velocity Motors 
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Joined: March 08, 2002
Location: Manitoba, Canada
Posted: June 04, 2002 at 10:32 PM / IP Logged  

Hey no problem. The only amps that do not follow this rule of thumb are the D class amplifiers. They are usually aroun the 1 % THD, but that's because the internal cross over is set to about 500 hz and because most D class amps are subwoofer amps, this type of levels in THD % is not audible .

Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
djkram650 
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Joined: July 16, 2002
Location: United States
Posted: July 16, 2002 at 7:22 PM / IP Logged  
I found that out the hard way. I purchased a Legacy L690 it gets to hot and goes on "protect". I asked my friends and they had the same problem with their old legacy. DONT BUY IT!
Static Revenger 
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Joined: May 08, 2002
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Posted: July 16, 2002 at 8:50 PM / IP Logged  

Once again if you want a good clean quaility amp that won't break your wallet get you a US Acoustics amp,nice price and a 3 year warranty to boot just to name a few. American Legacy Amplifiers - Page 2 -- posted image. 

American Legacy Amplifiers - Page 2 -- posted image.
GlassWolf 
Copper - Posts: 365
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Joined: June 22, 2002
Location: South Carolina, United States
Posted: July 17, 2002 at 8:49 AM / IP Logged  
remember also if you're looking at THD and S/N ratings on an amp kep these things in mind:
THD can be measured several ways, some of which are a bit underhanded and show better stats for the manufacturer.
THD and S/N have a relation between each other.
most people can't even hear distortion in an amp below 1%, and not below 10% in a car so that number again, is relative. don't rely on numbers alone.
-GlassWolf
Pioneer Stage-4, Orion, DynAudio, Fi
bigtymer 
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Joined: July 18, 2002
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Posted: July 18, 2002 at 1:09 PM / IP Logged  

 Everyone's saying that american legacy amps are bad.  i just bought one but i haven't hooked it up yet. my subs sound good just being hooked up to the factory system and i don't need a big difference in the sound.  so will the american legacy amp i bought be ok for me?

BigTymer
wudog3637 
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Joined: July 19, 2002
Location: United Kingdom
Posted: July 19, 2002 at 4:18 PM / IP Logged  
i recently bought a legacy that puts out 1800 watts. it made my american bass subs sound better then my rockford amp and subs. both were 15"s .
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