Lazy Singing Bush mono block build using THF51s

While searching for a physical drawing of the THF-51 I found the attached PDF which is quite fun (in itself) that a tube tester can be used for testing the SIT.
Most important I found the distance between the two holes (43.3 mm) from center to center.
From previous discussion here I learned that M4 thread should be cut into the heatsinks and not the alu panels which would have been the easy solution.
For the PCB mount however threads will be cut into the panels. Probably M3 threads.
I need to look more into the puck MOSFET......probably same solution there for mounting this device as for the SIT.
I will place the big devices a little bit below horizontal centerline to get the best cooling performans from the heatsinks.


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Ok, this will make it a lot easier. The panel is 10mm and I can make through hole threads in those panels.
Maybe the heatsink aluminium is a little bit harder than the panel aluminium...judged after I have drilled in both.....but not 100% sure about that.
I don't see many placing the power transistors "offset" (closer to the bottom) at the heatsinks.......most will just least the constructions I have seen here (by memory). By eye-catch I think even my VFET amp the bracket is placed closer to the top.
I make sense to place it lower as the hot air will go up.
when I built my monoblocks with IXYS- Mosfets, I used the 1/3 to 2/3-rule for the height of the Mosfets on the heatsink.
Horizontally - or from left to right- I made it 1/4 - 2/4 (betweeen the 2 Mosfets) - 1/4 (to the edge of the heatsink).
But however you want to do it - as long as it stays in the expected thermal region - all is good.
Dirk :)


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I have marked the holes for SIT and PCB on both SIT panels and I am ready to drill / cut threads........
I just have to remember not to drill 3mm / 4mm but a little smaller diameter....... for the M3 / M4 threads.
It would be a bad mistake to make.......


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Official Court Jester
Joined 2003
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It would be a bad mistake to make.......

Yep! I can understand. Nothing mentioned on those pics where North- South or East-West is...
And I don't know if I should look at this from the Beaver- or Hawk- perspective... 👀
greets from
Dirk :yes:

where is that picture of you , standing upside-down on your amp(s) ?

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Hello Meper,

the ESLs are from the Netherlands: Audiostatic ES300R
Much easier to drive than Logans. And better efficiency. My F5T-Monoblocks drive them with ease. Also the M2X can drive them pretty well.
But, as with most ESLs - don't let them work hard in the bass. Subwoofer helps ESLs a lot. And then they can play really loud.
My ones got new foils 5 or 6 years ago. Was a very good investment.