Here we go...
I am thinking of building a JLH Class A or one of it's derivatives. Graham's 2SC5200-based schematics look interesting.
So, to make it more interesting, I am thinking about building a water-cooled system. I would base it on this unit from Zalman:
I would need to machine some aluminum blocks to mount the transistors on with water passages. I have some ideas there.
I have a pair of those, along with some of their "mushroom"
fan/sinks. I was simply planning on bolting the block assembly
to a thick piece of aluminum plate with the transistor sandwiched
in between (metal side to the Zalman block).
Interesting idea. That also make "VGA blocks" (http://www.zalmanusa.com/usa/product...dx=90&code=013) that might work better for this.
I also use one of their copper CPU coolers in my PC, which is very quiet (http://www.zalmanusa.com/usa/product...43&code=005009) but may be too loud with two of them running.
When you say "any thoughts"... "thoughts" are only as far as I've got as yet. I've been doing a bit of reading and I think you'll find that copper has nearly twice the thermal conductivity as aluminium so I figure that when I get around to building something similar I'll look at copper. It's not too hard to machine and scrap metal people get 10mm thicknesses from heavy duty electrical installations. The other "thought" is oil instead of water. Again, just theory as yet but oil takes up thermal energy more readily than water. So in theory it is better at removing heat from small spaces (semiconductor junctions) than H2O. On the other hand I haven't checked any reduced flow issues that might arise with the different viscosity. The other disadvantage is that oil give up its energy more slowly than water but I figure that most of us could knock up a decent size heat exchanger from old car radiators or something. So to summerize "thoughts" I think copper and oil could be an elegant way of achieveing good technical results in this area. (and no doubt the extreme subjectivists will insist on "extra virgin olive oil" to get "smooth, pure highs and more faithfull reproduction"
BTW I think there are a couple of other threads on water cooling in the archives. I've got them in my "favourites" if the search mode doesn't deliver results quickly.
I thought of using copper block, but it is much more expensive than aluminum. I'll have to look around for scrap I guess.
Also, it is my understanding that water is the best cooling medium, without using a compressor and freon.
Oil is fine as Jonathan Bright said but water is easier to deal with in many cases. If you get a leak with oil you'll have less fun cleaning :)
10 years ago I converted a ceramic transmitting tube called 4CX250b from air to liquid cooled. This tube is still running in a high power VHF amplifier. Started with oil but ended with water because of leak inside the amplifier, it was a h*** to clean it up.
With five liter of water and a small heater radiator from an old car and a small quiet water pump I got rid of all noise from what usually comes from air cooling. The system had to take care of more than 400 watts of plate dissipation.
I would go for water :)
By the way I made an high current psu water cooled also but that was a little over kill I think :)
so it is preferred as the heat transfer medium.
This reminds me years ago when I was a Toolmaker. When
heat treating steels, water was used for a quenching medium
when highest hardness was required as a result of most rapid
cooling. Oil was used when a less hard but tougher treatment
was required as a result of it's slower cooling.
So, was talking to my brother about this (cooling medium) last night. He does a lot of machining work.
His first question was, "How hot do these things get?"
I told him I would need to keep temps below about 60C, so the answer was water. If you go close to 100C or above, oil is the solution (water boils).
Anyway, discussion moved quickly to designing a silent water coling system for amps. I'll post updates when and if they become available.
I am building 6 additional Pass amplifiers with the two Aleph's that i already have, together with the XVR1 as an active 4-way.
6 for 3-way loudspeakers, 2 for Susan Parker's Subwoofers.
Given the tremendous heat i am planning to use the water from my swimming pool to cool the amps.
(and heat the pool in winter :clown: )
On board of ships overheated steam or thermal oil is used for heating purposes above 100C/222F.
Steam mostly, because heat transfer with thermal oil requires huge amounts of it.
(think heating 10.000 tons of bitumen to 300 F )
Some oil tankers have coil heaters too, to prevent crude oil from become too thick.
Thermal oil is used for special purposes, when steam is a risk.
The most regular used cooling fluid was Freon, R12, for frigges, aircon, etc.
R12 was banned because of environmental hazard, by the HFC R134(a).
Nowadays there are alternatives for R134, because that too has downsides, it causes cancer.
I was thinking of machined copper ducts, with added alloy Papst vented heat tunnels attached.
The copper ducts would be cooled by water, driven from a floor central heating pump, a regular Grundfoss.
In case of emergency, the Papst vents are relay switched to full capacity for cooling, combined with thermal breakers for the powersupply of the amps.
My initial thought is using compressed air connectors for the hosing.
That way i have plenty cooling capacity, no sounds, and the heat doesnt make me dress as DestroyerX.
So how are you guys going to protect the amplifer in case of reduced or cut off water flow?
At that time I built my water cooled amp I searched for any type of flow interlock switch which would turn of the psu in case of cut off or reduced water flow. I did find but they were expensive.
Instead I used an flow indicator but I wouldn't recommend a solution with only flow indicator tough it's nice to look at with a small lamp behind it.
I did use an ordinary small central heating pump as Jacco vermeulen did, lots more flow than needed but I got it for free :D
A small heat exchanger from an old crashed SAAB 900 with an quiet fan attached at it did the job. Even tough I ran my amp pretty hard the cooling fan didn't start that often. The temp trip circuit was set to some were in the neighbourhood of 60-70C.
I often see water cooled systems made for computer which looks real overkill thinking of how much heat to remove. I heated my foot bath while running my amp and the high voltage had some cleaning effect as well :) That was an joke do not try!!!
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