Big promises, small delivery, beware...
Written: Nov 25 '02 (Updated Nov 27 '02)
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Pros: Inexpensive, small size, attractive enclosure (this is what you are paying for).
Cons: Mis-leading power, not bridgeable, no built-in electronic crossovers.
The Bottom Line: If you consider that this amplifier is actually a 'plain-Jane' amplifier with 19W RMS / channel, it is perfectly adequate.
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| rally-x's Full Review: Mobile Authority TA1001 Car Audio Amplifier |
Mobile Authority used all of the marketing games available when they printed the specification sheet and box for their TA-1001 stereo car amplifier. I bought the amplifier knowing that the 125W figure is meaningless. I read on two separate websites that this amp did put out 65W RMS however. Nope, it doesn't. I got burned (but since the amp was inexpensive, it doesn't hurt). Warning: The following discussion may be a bit on the 'nerdy' side (if you asked my wife), but it may help some of you choose the type of car amplifier to buy.
Techie Discussion: The Math Doesn't Add Up...
The only meaningful measurement of audio power is via the root-means-square (RMS) method. This is due to the alternating current (AC) property of an audio signal (speakers don't work with DC signals, they'd burn up).
This amp (TA-1001) is based on one Toshiba TA8210AH stereo amplifier integrated circuit. This chip is typically rated at 19Watts RMS per channel into 4 ohms when it is running off of a 13.2V supply (according to Toshiba). There is no power converter inside, the chip runs directly from the 13.2V car electrical system (when the engine is running). If I were to take a 4 ohm resistor and tie it across this same 13.2V input, I would get the equivalent of 30.8 Watts RMS (43.5W * 0.707) which would be the theoretical maximum from a 13.2 V supply. So where does 125W peak come from? From what I understand, this may be the theoretical maximum instantaneous peak (which a speaker can't respond to anyway) of a voltage spike out of phase with the reactance of the speaker. Not a very meaningful measurement if you ask me. A couple websites on the internet claimed this product is capable of 65 Watts RMS per channel (maybe if a continuous lightning bolt struck the roof of the car at the precise moment they were measuring the power...). I might also note that when this amplifier is operating up at 19W RMS, distortion goes up exponentially at this level (like most transistor based amplifiers). I have built a few audio HI-FI power amplifiers in my day, and repaired numerous others, so I know a little bit about this stuff.
Marketing hype aside, there is only one ACTIVE component in the amplifier, the Toshiba chip. The chip can power up via the remote output of your head unit. The amplifier features two RCA jacks for low level line input (no high level inputs here). There is an attenuation knob to match the level of the amplifier to the head unit. Speakers are connected via a four pin Molex type connector. The Toshiba chip internally bridges two amplifiers to come up with the 19W RMS rating, therefore, further bridging would not gain anything (except more distortion). The DC power inlet features a 5 amp fuse- no, you probably won't overload your alternator with this baby.
Believe it or not, I am keeping this amp. I have a small hatchback (Mazda RX-7) and I am using this amplifier to power an 8" dual voice coil tube subwoofer. My head unit has built-in filters so that I don't need an external electronic crossover for this amplifier. At 38W RMS (both channels into the subwoofer), I find that this amplifier has enough umph for my needs (I am obviously not into audio competitions). Since distortion is not as apparent at bass frequencies, it doesn't bother me. Since the price was not painful, I am willing to settle with this amp. I can't see myself telling my friends to go out and get one any time soon, however.
In order to get an amplifier that actually puts out 65W RMS, the amplifier requires an internal power converter to increase the output stage's working voltage. You can't get there without one. This feature cranks the price of the amplifier up considerably (this type of supply is not cheap). In hindsight, I should have realized that there was no way I was going to get that amount of power at this price. Price I paid includes shipping/handling (I purchased the unit on eBay). Moral of my story: you get what you pay for ;-).
Recommended:
No
Amount Paid (US$): 38
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Epinions.com ID:
rally-x
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Reviews written: 3
Trusted by: 0 members
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