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Class D Switching Power Amplifiers and Power D/A conversion

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Old 9th July 2005, 12:14 AM   #11
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by Bgt
power consumption idle = 97ma
full power, 1 Kc sinewave@100V peak(just not visibly distorting) on 8 Ohms(both channels) = 1450 ma
Absolutely a more environment and wallet friendly amp. than my NAD C272.

Is that 97mA for the + rail? Is it for one module or for both together?

Best regards

Gertjan
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Old 9th July 2005, 07:27 AM   #12
Bgt is offline Bgt  Netherlands
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all measured at the mains input. So idle is 97ma x 230V= 22VA.
Its the total amp. comsumption.
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Old 9th July 2005, 12:16 PM   #13
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by Bgt
all measured at the mains input. So idle is 97ma x 230V= 22VA.
Its the total amp. comsumption.

So 11 Watt per module. Assuming you have +-60V supplies, that would be 90mA per rail. The minus rail pulls a bit more current, so the + rail should be something like 60mA or so. Makes sense.

Best regards

Gertjan
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Old 9th July 2005, 05:11 PM   #14
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Default Bgt:

Yes, very elegant solution.

<<Concerning the position of the PCB, I tried to put it vertically but then 1 side of the T bone piece got too hot. The way it is now it is more evenly hot/cool on the PCB. There are cooling vents in the top and bottom cover just where the heatsink is positioned. Just look at the pic. Here you get your convection cooling airflow.>>
But for the cooling issue I wouldn't be concerned about T bone piece asymetric warming; that's its function. For the T bone piece you have more than enough with your heatsink. I understand that convective cooling will only benefit the heatsink-Mosfets, not the secondary transistor-opamps-coils mounted on the PCB.

Am I wrong?

Best wishes
Mauricio
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Old 9th July 2005, 06:39 PM   #15
Bgt is offline Bgt  Netherlands
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Quote:
not the secondary transistor-opamps-coils mounted on the PCB.
In the top lid there are also venting slots and because the PCB's are mounted on a quite low position in the housing there is a lot of air around the parts and this air comes out on top. The heatsink is mounted on the low side of the cabinet so there is still some space for the hot air to go out on top.
I measured the heat everywhere and the biggest heat comes from the heatsink/Tbone, not the 12Volt transistors and output coil. Yes they feel hot but have no heatsink. These are just minor heat generators. The output Fets have a idle current of about 60ma x 120 Volts which is about 7.2Watts to burn for each amp. Maybe more. Bruno will know.
If you feel the amps. temperature after playing for 8 hours you will feel that the heatsink has the biggest chunk of heat from the output fets. The heatsink will reach 55C.

I had them vertical in my first try of the UCD's in a housing used for my Crescendo's. But this was not the best solution. The housing was bigger and had a lower volt toroid(2x35V) so it did not get that hot.

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