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cambrigde a500 amp and acoustic 3311 speareks
cambrigde a500 amp and acoustic 3311 speareks
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Old 30th January 2013, 01:44 AM   #1
jurok007 is offline jurok007  United Kingdom
diyAudio Member
Join Date: Jan 2013
Unhappy cambrigde a500 amp and acoustic 3311 speareks

hi everyone, last month i got a pair of "Acoustic 3311 studio monitors speakers" (8 ohms, 125w ) , as do not have an amp i could not chech them. only today i bought a Cambridge audio a500 amp, when i set up a system and turned on, it came a noise (uuuuuuuuu) and from amp came smoke. after i opend amp i see power transistor sap 15 was blown. why do that happend, could my wiring be wrong ?? how to do normal (not bi-iring) wiring for 4 channel amp and 2 speakes ? thank you.

Last edited by jurok007; 30th January 2013 at 01:52 AM.
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Old 30th May 2013, 11:08 AM   #2
OXAUDIO is offline OXAUDIO  United Kingdom
diyAudio Member
Join Date: Sep 2006
Having recently spent quite a bit of time checking an A500, and reading posts on this and another forum about them, I have found that the SAP15N &SAP15P Darlington Pair o/p
transistors used in these can fail. Often the cause seems to be that too low impedance speakers have been used, together with the fact that, according to some people, an inadequate heatsink is used. The later type SAP16N &16P devices are available from Rapid ElectronicsElectronic Components from Rapid - the Electronic Parts Specialist I doubt that your wiring was wrong. The two speaker connections for each channel are internally paralleled so as long as the speaker +ve goes to one of the red terminals, and the -ve to a black one there should be no problem. 8ohm speakers should be used with the A500.
It just occurred to me that there are maybe a couple of other shortcomings with the 500
(1) No 'A/B' Speaker switching, & (2) No internal cooling fan as fitted to many other amplifiers, receivers, etc.
P.S. Have you read the other threads about the A500? There are quite a few on here!!
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Old 30th May 2013, 05:46 PM   #3
jaycee is offline jaycee  United Kingdom
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Join Date: Apr 2004
Location: Norwich, UK
The main problem with the Cambridge A500 is that the internal heatsink used is made from folded sheet metal, and is rather poor. There is also no DC protection circuitry so there's a real risk of speakers being damaged.

It is possible that your wiring was fine, but the speakers were not and they shorted out the amp.
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