The weight of each heat sink is approximately 0.860kg.
L : 233MM
W: 55MM THE TOP FINS
H: 82MM
I was thinking mounting them vertical or slightly at an angle like a pair of wings 😉
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Good idea on the vertical mounting, IMO.
Once you have figured out how many watts of heat you'll need to dissipate via each sink, you could test them with an appropriate power resistor to see how hot they get.
Or just try them out with your amp board, before you build up a case.
It would be a pity to build the case and then find that the sinks were too small to do the job.
I don't recall exactly, but the heatsink I used when I built my (one channel) Pass F6 was about 3+ kg and the MOSFETs were about 60C. Obviously a more efficient shape (more fins, longer fins) could be more effective - my sink was the old style with fewer, thicker fins.
Yes, the heatsink may be a little small for two channels. I built a class A amplifier with about that much quiescent power, and I used two SK90 0.6 K/W heatsinks, and they got hot! 
They are about 190 mm x 50 mm x 100 mm finned.
Well done on your choice! 🙂
They are about 190 mm x 50 mm x 100 mm finned.
An externally hosted image should be here but it was not working when we last tested it.
Well done on your choice! 🙂
L : 233mm is actually the height.
If you cut these in half anf mounted them vertically beside each other they will provide about 40% more cooling.
Cut them into 4 pieces and you get 100% more cooling from the same weight of sink.
Thats interesting, so you think cutting them into four segments, then remounting them onto another piece of aluminium will more cooling?
I wanted to keep the original shape and build of the heatsink, and if i need to i could always bolts more heat sinks to it.
If you cut them, you can't connect them again - that defeats the purpose. I am no expert, so I stand to be corrected.
Either way, if you do cut it into four, I still don't think you'll have enough heat sinking. I'm not sure how the biasing is set up on these amplifiers. For "efficient" class A, you need 1.5 A, for normal class A you need 2.8 A for 30 W.
At 1.5A:
Quiescent dissipation is 38 W per output transistor. With 1 K/W on one transistor, the heatsink will get to 38 Celsius (above ambient). The case will be at more or less 60 Celsius (above ambient).
At 2.8A:
Quiescent dissipation is 70 W per output transistor. With 1 K/W on one transistor, the heatsink will get to 70 Celsius (above ambient). The case will be at more or less 100 Celsius (above ambient).
This assumes a supply of 50V (+-25V rails).
If you need 2.8 A or thereabouts, 1 K/W isn't enough. I mean, it should be fine for a while, but silicon likes to be kept as cool as possible (in general). You'll probably need 0.5 K/W per transistor. I'm going to guess your heatsink is going to be closer to 1.2 - 1.5 K/W per each of the four if you cut it. As it is, I'm going to guess it's at around 0.5 - 0.7 K/W.
This is hopefully a guideline at best. Please don't follow this as accurate.
Either way, if you do cut it into four, I still don't think you'll have enough heat sinking. I'm not sure how the biasing is set up on these amplifiers. For "efficient" class A, you need 1.5 A, for normal class A you need 2.8 A for 30 W.
At 1.5A:
Quiescent dissipation is 38 W per output transistor. With 1 K/W on one transistor, the heatsink will get to 38 Celsius (above ambient). The case will be at more or less 60 Celsius (above ambient).
At 2.8A:
Quiescent dissipation is 70 W per output transistor. With 1 K/W on one transistor, the heatsink will get to 70 Celsius (above ambient). The case will be at more or less 100 Celsius (above ambient).
This assumes a supply of 50V (+-25V rails).
If you need 2.8 A or thereabouts, 1 K/W isn't enough. I mean, it should be fine for a while, but silicon likes to be kept as cool as possible (in general). You'll probably need 0.5 K/W per transistor. I'm going to guess your heatsink is going to be closer to 1.2 - 1.5 K/W per each of the four if you cut it. As it is, I'm going to guess it's at around 0.5 - 0.7 K/W.
This is hopefully a guideline at best. Please don't follow this as accurate.
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No this helps Mrcloc, am i being silly here? If i cut them how am i supposed to hold them together and upright? If they aren't connected how is the heat dissipated?
Anyway i probably wont cut them just add more aluminium finned shaped heatsinks to it.
hhhhhmmmm efficient or normal? Well we want 30w of power. Just need to source the right output transistors. Any ideas?
Im ordering some bits today:
Hiraga super 30W class A w/ current source + kubota reg partial assembled kit ! | eBay
Hiraga super 30W class A amplifier kit ! | eBay
not sure what the difference is between these two kits?
Anyway i probably wont cut them just add more aluminium finned shaped heatsinks to it.
hhhhhmmmm efficient or normal? Well we want 30w of power. Just need to source the right output transistors. Any ideas?
Im ordering some bits today:
Hiraga super 30W class A w/ current source + kubota reg partial assembled kit ! | eBay
Hiraga super 30W class A amplifier kit ! | eBay
not sure what the difference is between these two kits?
I'm with you on this- those sinks look like they could be mounted vertically-probably on the corners of a tall enclosure- or horizontally.
Cutting them into sections and mounting them side-by-side would be difficult.
Another possibility would be to put the sink into a 'pipe' with a fan pushing air through the fins. Fans seem to work for some builders but wouldn't be my choice for hi-fi. I just (finally) got rid of a TV PVR/Cable box with a noisy fan. That said, there are some very quiet fans nowadays, I think.
DIY can be a difficult thing to stick to when it's so much cheaper just to buy ready made. Speakers is one area where it's possible to make something much better for the same price and tailor to your own preferences and room. Amps all sound the same after all....................................
True, but once i start something i like to finish it to the end. And building a super class A amp is going to happen!
As you know scott i got a few speaker enclosures i am working on so i want a suitable amp.
As you know scott i got a few speaker enclosures i am working on so i want a suitable amp.
That's debatable from a South African's perspective.
If all amplifiers sound the same, then it's maybe true. 😀
Good! Sometimes it's interesting to 'see what's on the market' and to be able to compare my builds with commercial gear.
Off topic:
'Full range' around this forum usually isn't, if you like bass. But, as has been already said, we have to journey through these stages in our lives!😀
One motivation for my explorations into SS amps is to get something to better drive less-efficient commercial speakers which are going very cheaply (used) around my city as seniors 'downsize' to different living spaces.
I'm going to build up my F6 and perhaps another class A project, but I think I'm 'going back' to a tube amp eventually.
Having an amp with plenty of reserve to drive different speakers is a good thing, IMO.
😡
That's a mini Aleph by the way, the builder gives details here:
http://vi.raptor.ebaydesc.com/ws/eB...437&category=122649&pm=1&ds=0&t=1492007598516
I personally have a problem with the flagrant profiteering of Pass' work on Epay 🙁
Best,
Anand.
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