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Old 8th May 2008, 08:39 AM   #1
N-Well is offline N-Well  France
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Default Aleph 30 - IRF9610 Cooling

Hi,

I would need some little help !

I've just finished to build an Aleph 30. Not yet listened to it, only
made a couple of measurements.

I've noticed the 3 9610 are pretty hot, probably about 50C or more . Is it recommended to heatsink them or could I leave them without heatsinks ?

Normally, looking to the mosfet data sheet, they should be able to handle it, but ???

My problem is that I mounted them on the Brian GT board and
there's no the space for heatsinks... I would hate to have them remote...

Otherwise no issue of output zero drift Vs time, stays below 10mV to 30mV.


cheers
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Old 8th May 2008, 09:04 AM   #2
Zen Mod is offline Zen Mod  Serbia
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Default Re: Aleph 30 - IRF9610 Cooling

Quote:
Originally posted by N-Well
Hi,

I would need some little help !

I've just finished to build an Aleph 30. Not yet listened to it, only
made a couple of measurements.

I've noticed the 3 9610 are pretty hot, probably about 50C or more . Is it recommended to heatsink them or could I leave them without heatsinks ?

Normally, looking to the mosfet data sheet, they should be able to handle it, but ???

My problem is that I mounted them on the Brian GT board and
there's no the space for heatsinks... I would hate to have them remote...

Otherwise no issue of output zero drift Vs time, stays below 10mV to 30mV.


cheers
just chill ;

or mount them , separately isolated , on plain alu sheet ;

in other words - mount sheet on them
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Old 8th May 2008, 03:07 PM   #3
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If they're running at 50 degrees C, something's very, very wrong. They should be running at something on the order of .25W, which is nothing for a TO-220 case. I generally start thinking about using a heatsink on a TO-220 once it gets over about .5W dissipation.
Check the front end bias if you feel they're running hot. The easiest way to do that is to measure the voltage drop across the current source's Rsource, then apply Ohm's Law to get the current. You should see about 20mA total bias for the front end differential. Then measure the voltage drop across the 392 Ohm load resistor and calculate that current. It should work out somewhere around 10 mA...this will vary somewhat so don't get frazzled if it's off by one or two mA. If, however, the vast majority of the front end current is going through one or the other of the MOSFETs in the front end differential, you probably need to address MOSFETs matching issues.

Grey
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Old 12th May 2008, 01:20 PM   #4
N-Well is offline N-Well  France
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Join Date: Feb 2006
Location: Z french Alpes
Thank you Guys for the answers.

Before I've read Grey's answer, I 've installed small U form Aluminum DIY heatsinks on the 9610s. Much cooler now.

I will check the current and Drain-source voltages again. Originaly before posting my question I did it already and I had something like 0.5W on the current souce 9610 one (the hotest indeed).

By the way, I could listen to my new Aleph 30. I use it on my low frequency drivers (<300Hz, 6dB/oct slope) .. I love it : Voices are smooth and bass are well controlled enough. Sound stage sounds more present ( Comparison versus 2 very different amps used on my LF channels: DIY Class T amp and also Nelson's F2 like amps)

cheers.
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