Hi, maf, you probably can find suitable heatsinks locally if you search for heatsinks purposed for high power ssr relays.
They won't be cheaper, but you can avoid the shipping cost.
They usually look like the Element14's one. Worth a try.
They won't be cheaper, but you can avoid the shipping cost.
They usually look like the Element14's one. Worth a try.
Try Conrad
Conrad Heatsinks - Products
Alternatively, surplus CPU coolers and PWM fans will cost you about $50 - $70 for the pair. See above examples by Vunce.
Hi. Thanks for the info of the heatsinks.
Conrad looks good, they have many sizes, like this one MF30-151.5: 151.5mm height x 300mm long x 48mm width. Weight at that size is 2.1kg
What would be the minimum heatsink size for the MoFo?
The Conrad prices make the heatsinks @ around less than 50% of the rest of the components. That's better!
Conrad looks good, they have many sizes, like this one MF30-151.5: 151.5mm height x 300mm long x 48mm width. Weight at that size is 2.1kg
What would be the minimum heatsink size for the MoFo?
The Conrad prices make the heatsinks @ around less than 50% of the rest of the components. That's better!
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Conrad has plenty to choose from. Think of a rating of 0.50c/w as a minimum point. This will let you burn off ~50w while keeping thermal rise close to 25c. The challenge is that Conrad rates their sinks at 80c which doesn't exactly translate to the 50c level where we use them in amps.
Looking at their catalog, I'd say the MF-25, MF-30, or MF-35 configurations will work well. Choose either the 100mm or 150mm lengths. General rule for sinks is larger = better. Go bigger than you think, many people report building new amp circuits in old chasses, so keep an eye toward the future as well.
Looking at their catalog, I'd say the MF-25, MF-30, or MF-35 configurations will work well. Choose either the 100mm or 150mm lengths. General rule for sinks is larger = better. Go bigger than you think, many people report building new amp circuits in old chasses, so keep an eye toward the future as well.
In most lands, IF you can tolerate a fan, your best buy will be Pentium heatsinks. They run from cheap to free (if you find the PC graveyard). The usual type can be drilled (beware drilling fancy liquid-cooled sinks!). The fan is nominal 12V DC. Because you also want to under-run it for noise, you can feed your 19V through a resistor. Try 100 Ohms 2 Watts; actually get a baggie of 47 Ohm 1W and series them to taste/touch.
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For a "standard" heatsink we know how to calculate easily the dimensions regarding the power to dissipate.
How do you calculate it for a heatsink with a fan ?
How do you calculate it for a heatsink with a fan ?
Rule of thumb is fan increases thermal capacity by 10x. A well designed forced convection radiator with optimized thin fins and heat pipes is in a different league. Go with CPU heat rating in that case. Typically larger cpu coolers with fans handle 150w no problem. Look at my MOAMOFO.
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You must use name brand Noctua fans for absolute low noise. They have done a lot of R&D into every little fluid dynamic trick to reduce noise. It's inaudible with my ear 10cm away - cannot tell it is even on. It is quite amazing - my other fans sound like a jet turbine by comparison. Get the PWM fan and get the variable PWM speed controller with temp sensor and adjustable fan speed thresholds.
I am not paid by Noctua - just really like their product, it is very different from any other fan.
Here is the spec for the 120mm Noctua, noise is 26.2dBA (that is way way below the ambient noise in most homes):
NF-A12x25 PWM
With the included low noise adapter (probably a bunch of series diodes to drop voltage) to take it to 450rpm, noise is 18dBA...
Example of PWM fan controller that I use, these work very well:
https://www.ebay.com/i/362565930230?chn=ps
I am not paid by Noctua - just really like their product, it is very different from any other fan.
Here is the spec for the 120mm Noctua, noise is 26.2dBA (that is way way below the ambient noise in most homes):
NF-A12x25 PWM
With the included low noise adapter (probably a bunch of series diodes to drop voltage) to take it to 450rpm, noise is 18dBA...
Example of PWM fan controller that I use, these work very well:
https://www.ebay.com/i/362565930230?chn=ps
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The Pentium-type sinks which I showed can take a 86 Watt CPU.
CPU thermal management is different from audio amplifiers. I would derate to half for audio amp comfort. 43 Watts is essentially 20V 2A which is a good point for a MoFo.
Yes, fan noise is a real issue. And unlike AB amps, the MoFo won't idle cold in the silent parts.
C1 still in place.
I have resolved the hum from my pre. The 'direct' input across the load resistor is better than the conventional input but slightly unfair comparison in that I only have Vishay MKT 1813 caps fitted at the moment.
I have some Russian K78-34 to try and will report back. Also intend to replicate my preference across the 6800uF output cap.
I am pushing my CPU coolers (probably rated 120w to 150w) close 160w (4.35A at 37v) with no issue. Mosfet body temp is about 60C as measured with IR thermometer on the aluminum clamp bar (with Kapton tape for 0.9 emissivity). Air temp of the CPU cooler fins is about 40C. Noctua 80mm PWM is running in still inaudible mode. There is a temp sensor in air stream and it kicks speed up if it ever gets too warm. It has 45C threshold for speedup.
Just a copule of questions please:
What are the dimensions of the heatsinks you use?
Am I correct in that your heatsinks are not designed to take fans directly, you just position the fans over one of the ends? Are these types slightly lower rated once you strap the fans on?
Little Eddy,
Please refer to the nice post 1691 where Vunce gives dimensions and part number to look for when searching eBay for a surplus Dell CPU cooler. This one is nice because it has a big copper pad that makes mounting a large TO-264 easier. The dimension was designed for a Dell OEM shrouded duct cooler but an 80mm fan fits perfectly as you can see in Vunces photo below post 1691.
Build This MoFo!
Here is the fan controller you can use:
12V PC CPU 4 Wire Fan Temperature Control PWM Speed Control W/ Alarm *** | eBay
Please refer to the nice post 1691 where Vunce gives dimensions and part number to look for when searching eBay for a surplus Dell CPU cooler. This one is nice because it has a big copper pad that makes mounting a large TO-264 easier. The dimension was designed for a Dell OEM shrouded duct cooler but an 80mm fan fits perfectly as you can see in Vunces photo below post 1691.
Build This MoFo!
Here is the fan controller you can use:
12V PC CPU 4 Wire Fan Temperature Control PWM Speed Control W/ Alarm *** | eBay
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Use this one
SILENT WINGS 3 | 120mm silent high-end Fans from be quiet!
and fan noise won´t be an issue anymore.
It´s 16,4dB at 12V.
I drive them with 9-10V. It´s inaudible. 😉
SILENT WINGS 3 | 120mm silent high-end Fans from be quiet!
and fan noise won´t be an issue anymore.
It´s 16,4dB at 12V.
I drive them with 9-10V. It´s inaudible. 😉
In for a penny, in for a pound. Also ordered a pair of the pwm controllers so will test how much energy I can reasonably sink without the supplied fan working too noisily.
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You want the 80mm Noctua fan for silent operation. I’m quite sure the stock Dell fan will be noisy.
Is this Noctua fan referred to by XRK971?
Noctua NF-R8 redux 1800 PWM 80x80x25mm. 4-pin PWM. 1800RPM
https://www.lazada.com.my/products/...hlistcategory.list.31.317e6a74JdJt63&search=1
Noctua NF-R8 redux 1800 PWM 80x80x25mm. 4-pin PWM. 1800RPM
https://www.lazada.com.my/products/...hlistcategory.list.31.317e6a74JdJt63&search=1