# Old vs new Boston GTA amplifiers?



## ZAKOH (Nov 26, 2010)

I remember reading on a russian web site that the older Boston GTA-504 measured 70watts/120watt RMS at 1% THD, even though the factory rating was only 50watt/80watt RMS. It's fair to assume that all older GTA amplifiers were "underrated". Now, Boston Acoustics sells a new 2011 line of GTA amplifiers. Their RMS wattage rating has gone up. The new 4-channel GTA-704 is rated for 70/125watt RMS. The thing that I wonder about right now.. are the new GTA amplifiers "underrated" as before, or did people at Boston Acoustics realize they can bump the specs of the older GTA amplifiers and offer them as new and improved line?





PS: I am sorry. I posted this in wrong thread. Can it be moved?


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## Danometal (Nov 16, 2009)

I'm wrestling with the same thing as I consider which 4 channel to buy to match my 2011 GTA-1000m (excellent sub amp BTW).

The THD ratings went way up along with the power ratings on all 2011 GTA models.


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## ZAKOH (Nov 26, 2010)

Danometal said:


> I'm wrestling with the same thing as I consider which 4 channel to buy to match my 2011 GTA-1000m (excellent sub amp BTW).
> 
> The THD ratings went way up along with the power ratings on all 2011 GTA models.


Are you referring to 0.05 vs 1% THD reported in the old and new literature? I suspect we have here the same old problem where marketing people have no clue what THD test is about. The RMS power test is done at fixed THD (usually 1%). The THD test is done at fixed wattage (usually 1watt). They frequently mess things up, reporting the RMS test THD as the THD test measure (e.g. amp THD is 1%) or that supposedly RMS is measured at 0.05% THD. Both are nonsense.


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## Danometal (Nov 16, 2009)

ZAKOH said:


> Are you referring to 0.05 vs 1% THD reported in the old and new literature? I suspect we have here the same old problem where marketing people have no clue what THD test is about. The RMS power test is done at fixed THD (usually 1%). The THD test is done at fixed wattage (usually 1watt). They frequently mess things up, reporting the RMS test THD as the THD test measure (e.g. amp THD is 1%) or that supposedly RMS is measured at 0.05% THD. Both are nonsense.


Sorry for the late response. I've been on CA.com (They seem to generally be more SPL oriented than here). 

Anyway, I wasn't aware of the different tests for different specs. I always thought it was THD x rated RMS, and that's it. Further, I thought Boston pushed their GTA-800m amp harder to get the 1000 watts, but increased the THD accordingly, and then threw an extra fuse on it, and then called it the new 2011 line.

Either way, I feel like I got a quality amp for only $239 on Sonicelectronix (but they since went up to Crutchfield's pricing of $350, not sure why).


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## ZAKOH (Nov 26, 2010)

Have you played with q-tune on your BA amplifier? My understanding that it's like bass boost, except that it's done at the subsonic filter frequency. If this is the way it works, it seems like this is the way to get a ported box frequency response from a sealed box sub. This is the only reason BA amp is on my mind.. and the price. I think the fact that all controls and connectors are on one side is actually a drawback for my install. I would have preferred to see power and speaker connections on one side and all controls and RCA connections on the other side, which is the more usual layout.


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## Danometal (Nov 16, 2009)

ZAKOH said:


> Have you played with q-tune on your BA amplifier? My understanding that it's like bass boost, except that it's done at the subsonic filter frequency. If this is the way it works, it seems like this is the way to get a ported box frequency response from a sealed box sub. This is the only reason BA amp is on my mind.. and the price. I think the fact that all controls and connectors are on one side is actually a drawback for my install. I would have preferred to see power and speaker connections on one side and all controls and RCA connections on the other side, which is the more usual layout.


I haven't played with mine, no. I just have it turned all the way down (counterclockwise), and my subsonic as low as it goes (I think 10 hz). I have a ported box, but it's tuned to 25 hz, and doesn't unload ever, even with a 20 hz test tone. Also, all the controls on one side was best for me, as my amp rack sits between the back of the sub box and the rear fold down seats 
(trunk car), so the controls are accessible from inside the car. Other than the controls location, I would totally recommend that amp for sure! CEA-2006 certified, clean sound, reliable, very small footprint, doesn't run hot, looks nice, etc.


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