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AB International amps opinons needed


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I've got an 1100a that's been used for around 12yrs or more.The only thing ever needing repaired was a bad vol. pot.This thing is an "agedhorse" ;) & absolutely rock solid reliable.

I do have a ? for agedhorse.Is Mike[A B] Butler the friend of yours who designed this amp?I've seen his name on the pro sound forum & wandered if he was the person behind the design?

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I do not know Mike personally, but he may have been one of the service dept guy. There was a Mike that worked there, but I didn't have much contact with the production folks. I have had no contact with AB over the past 5 or 6 years, other than one of the original owners. The company [changed hands] several times since then.

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Thanks AH for PM me, I scored a 1100A for dirt cheap after reading this forum I bought it. These are huge amps and very heavy but it works great,and I really appreciate the input you guys gave about them. I didn't know that much about them until recently, seems that they have a good reputation in the SR biz.;)

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Originally posted by twostone

Thanks AH for PM me, I scored a 1100A for dirt cheap after reading this forum I bought it. These are huge amps and very heavy but it works great,and I really appreciate the input you guys gave about them. I didn't know that much about them until recently, seems that they have a good reputation in the SR biz.
;)

Congrats.Ours has been an excellant amp for years. They are very beefy amps,but I'll gladly deal w/ the size/weight issue for the realiability that it has given over the years.

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  • 11 years later...
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Old thread, but I happen to have a 1100a that seems to get quite hot, and upon further hunting I have discovered a resistor R80 ( 5.6 K-ohm ) 2 watt that seems to have been charred? Wondering if anyone with more knowledge with these amps could enlighten me a bit? The resistor is only charred on one of the 2 identical boards??

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If this is overheated, it's the primary indicator that one or both of the high rail commutating switches is shorted. (or something in the corresponding circuitry is improperly turning the switch(es) on.

 

This is a fairly difficult circuit to troubleshoot, you (or your tech) needs to really understand how the circuit works as there are the high and low rail commutation as well as the ground commutation of the low rail. It's a unique application of class H. The guy who developed it was an engineer for Altec, and when they dismissed the class H technology is impractical they started AB Systems. Class H (and G) of course became the standard topology for larger power amps until class D took over.

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