I have a very novice level understanding of how amplifiers work, so please bare with my ignorance. I understand that a bridge rectifier converts or at least plays part in the conversion of AC to DC power. I've seen some amplifiers with heat sinks on them, like this one here. Yet others do not, like this one. The first one is a 2 channel 75 watt per channel stereo amplifier. It has two bridge rectifiers (I presume for each channel), each with a heatsink. The second one is a 200 watt mono block. It has one bridge rectifier, no heat sink. Obviously the heat sink is there to dissipate heat. The question is why does an amplifier with higher output ratings not have a heat sink whereas the the lower power one does?
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Bridge Rectifier
- Thread starter SEKLEM
- Start date
Firstly, the monoblock amplifier has a rectifier formed of four individual diodes, so there's no provision or need for heatsinking. The other amplifier has a bridge rectifier which normally gets warmer as the diodes that make it up are enclosed in plastic and don't radiate as easily. The monoblock amp is also a Class G amp, so will have less static power consumption so there will be less heat in the rectifier. The stereo amp will have higher static consumption, and it's also possible that the designer preferred to take a more conservative approach to heat. I've not come across bridge rectifiers with separate heatsinks, normally they are screwed to the chassis which acts as a heatsink.
S
S
To answer, we also need to know more about class of operation and idle current of the amplifier. If it is class A, the idle current may be as high as 2A and then heatsinking of the rectifier diodes is a must. It may be also highly biased class AB, for example I use 4 pairs of output power transistors per channel, each pair biased at about 100mA, so again heatsink on the bridge rectifier is requested.
Or it might be a classB with few mA of idle current and then most probably the heatsink would not be needed, as the average current through the rectifier would be quite low.
Dimitri
Senior Member
A) What they said above
....plus a few other speculative reasons: mounted bridges are easier to replace, take no space on the board, give a sense of "robusteness" and let's not forget that depending on the designer (or target market) some bridges may just have magical properties so although the heatsink is "there to dissipate heat", it's not the only reason to use it .
- Thread Starter
- #5
I forgot the Outlaw was class G. The Niles (first amp) is a class A/B. The bias on the Niles would seem to be more B since it runs very cool, or is that assumption incorrect?
It could be lightly biased, or it could be that it runs cooler due to better heat sinking. One would have to see a circuit diagram and what bias it's set to.
S
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