This is the heatsink that I used:
Large Forced Air Heat sink
With the fans, the heatsink fins are warm.
Large Forced Air Heat sink
With the fans, the heatsink fins are warm.
Paul,
Another cooling option is to make a platform with a fan in it and place it under the amplifier. Provide cooling holes in the amplifier chassis bottom and top plates to allow the fan to blow air into the chassis and cool the amplifier from the inside.
Zen Mod Babysitter
Another cooling option is to make a platform with a fan in it and place it under the amplifier. Provide cooling holes in the amplifier chassis bottom and top plates to allow the fan to blow air into the chassis and cool the amplifier from the inside.
Zen Mod Babysitter
Those heatsinks you posted look incredibly capable. I'm surprised they even need a fan much less two. I suppose the fins are a little close for efficient convective cooling. Shipping from Canada costs more than the heatsinks! You had a chassis built to fit the heatsink?
I like ZenMod's idea but I bet it isn't going to be enough to blow air through the inside of the chassis. Right now my best idea is to use a 400mm 5U chassis and have one fan mounted on the heatsink with the THF-51S. I'll put the IXTN40P50P on the other piece of the heatsink. I couldn't figure out from the datasheet how much heat the IXTN40P50P puts out but I assume it isn't that much? Also, can the IXTN40P50P be mounted directly on the chassis or does it need an insulating sheet in between?
Good to know a lower Iq is also an option.
I have found that getting a good thermal connection between the heatsinks and the baseplate helps a lot. I add thick aluminum L brackets between the bottom edge of each heatsink and the baseplate. The Modushop chassis need to have the lower steel bracket replaced to make this happen, and it is worth the effort to do so.
The intent is to have the entire chassis involved in power dissipation.
The intent is to have the entire chassis involved in power dissipation.
The chassis were from Aliexpress.
The fins are too close on those heatsinks for natural convection so forced air is necessary.
The Babysitter may work. Zen Mod's Babysitter has one fan but there is no reason why two fans cannot mounted in the base, one for each side, or even four smaller fans. This is DIY.
The IXTN mosfet can be mounted directly on the heatsink. Only thermal transfer paste is needed.
How much heat each component dissipates depends on the voltage drop across it and the current through it. If the current is 3A and the SIT drops 33V, the 5x0.1R resistors drop 5x0.1Rx3A=1.5V. The P-Mos drops the rest. My power supply puts out about 64V under load so the P-Mos drops 64V-33V-1.5V=29.5V
So the SIT dissipates 33Vx3A=99W, the resistors dissipate 1.5Vx3A=4.5W, and the P-Mos dissipates 29.5Vx3A=88.5W.
The fins are too close on those heatsinks for natural convection so forced air is necessary.
The Babysitter may work. Zen Mod's Babysitter has one fan but there is no reason why two fans cannot mounted in the base, one for each side, or even four smaller fans. This is DIY.
The IXTN mosfet can be mounted directly on the heatsink. Only thermal transfer paste is needed.
How much heat each component dissipates depends on the voltage drop across it and the current through it. If the current is 3A and the SIT drops 33V, the 5x0.1R resistors drop 5x0.1Rx3A=1.5V. The P-Mos drops the rest. My power supply puts out about 64V under load so the P-Mos drops 64V-33V-1.5V=29.5V
So the SIT dissipates 33Vx3A=99W, the resistors dissipate 1.5Vx3A=4.5W, and the P-Mos dissipates 29.5Vx3A=88.5W.
Vunce, Nothing wrong with 60V. My power supply happens to put out about 64V so that is what I use. The voltage also varies, depending on the time of day. A bit of fluctuation in voltage and amplifier performance is no big deal. With the generous amount of distortion (compared to stereotypical high end amplifiers whose distortion numbers have a lot of zeros), a bit of fluctuation and variance is no big deal, at least for me.
I hate asking this question because it makes me feel stupid/ignorant (which I am when it comes to circuit design), but P-Mos is the generic term you are using for the IXTN40P50P? So it will be dissipating nearly as much heat as the SIT? That certainly explains the need for 2 fans on your mono block.
Also, maybe you could use 63V caps 👍Perfect!
No added heat from bridge rectifiers, a few less watts for the chassis to dissipate
sole reason why I'm using active babysitter during Summer with each of my amps is my OCD regarding caps inside, not actually heatsink temperature (practically none of amps having less than optimal kilos of aluminum)
So:
- steel is lousy thermal transfer material, good enough ( even if lousy, big enough) to mount diode bridges (with thermal paste) on it, but for anything else .....
- why heating caps even more
-why complicating physical construction to enable thermal transfer that way, when introducing 5mm spacers (high screw washers) for both bottom and top cover will give you more?
-why complicating physical construction to enable thermal transfer that way, when using nice Babysitter will give effect of increased feet, covers with spacers .... and then some?
anyhow, any further change of case construction should dictate bigger price of same, so - just buy bigger case, pronto
Hello amp-builders,
as TungstenAudio and pinholer mentioned - with a lot of aluminum and especilly as Monoblocks -
you can transfer a lot of heat away... passively.
50W-SE-Schade-amps running at a bias of 3.2 A and complementary IXYS-Monoblocks running slightly
below 3 A. Hot!
Have fun building Ben Mahs-amp!
Cheers
Dirk
as TungstenAudio and pinholer mentioned - with a lot of aluminum and especilly as Monoblocks -
you can transfer a lot of heat away... passively.
50W-SE-Schade-amps running at a bias of 3.2 A and complementary IXYS-Monoblocks running slightly
below 3 A. Hot!
Have fun building Ben Mahs-amp!
Cheers
Dirk
