Build This MoFo!

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mikelm

mikelm

Member
Joined 2003
I'm into chokes enough to know that they generate a negative rail.

My 25V + 25V amp will probably not have a SE follower. The sinks aren't big enough to support the desired bias current.

. . . and when I build a MoFo it will almost certainly have a choke - but not sure which one yet.
 
H

Holzarbeiter

Member
Joined 2014
Paid Member
https://www.heatsinkusa.com/

Drew, I've never had any luck on the website. Can't figure it out to get the proper measurements. Always go back to making my own or ModuShop.

MR has the right idea now with UMS to make it so much easier for everyone and a good source to get.

I've made for Newark problem 2 D/M amps. One BA3-3 to drive them still testing. And as I have the last Newark sink they sold that is the wrong size need to make another blown amp to use up that sink. 6L6 has the right idea on how to make a MOFO. There will be more made like that now.

https://www.diyaudio.com/community/threads/build-this-mofo.313649/post-7404931
 
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dliscomb

dliscomb

Member
Joined 2018
Not sure what you mean by "never had any luck on the website", @Holzarbeiter. I used the "degrees per watt per 3 inches" rating for each heatsink to find one that would comfortably keep the MoFo FETs cool enough. In the end, 3 inches of the 10.08" stock (https://heatsinkusa.com/10-080/) has been doing an adequate job. And that's with crappy, non-Keratherm insulators behind the FETs.

Pictures of my MoFo here: https://www.diyaudio.com/community/...assis-sample-image-inside.390293/post-7126574

Kind regards,
Drew
 
e_fortier

e_fortier

Member
Joined 2001
Holzarbeiter said:
UMS is the way to go. Newark is not stocking anymore and a pain to deal with. Modushop sinks still best deal. Hard to find anything Avnet that will werk.
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Modushop heatsinks are just OK, many companies offer similar heatsinks but with longer fins. The typical 40mm heatsinks isn’t good enough when you know there’s better stuff out there. I even sent an exemple of such heatsinks with company info to Modushop and it went nowhere. Maybe Gianluca can look at this one more time.
 
H

Holzarbeiter

Member
Joined 2014
Paid Member
dliscomb said:
"never had any luck on the website", @Holzarbeiter. I used the "degrees per watt per 3 inches" rating
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Drew as far as I could tell the sinks there are not tall enough. For me.
I can't fit Dual Mono and esp 2 D/M amps in one case. I fill a 5U to the brim. It's not heat dissapation I worry about.

Now that MR is going to UMS there is a possibility that more MOFO's can be built without the problems of tapping threads to the in-experienced.

Best, H.
 
Gianluca

Gianluca

Member
Joined 2012
modushop.biz
e_fortier said:
Modushop heatsinks are just OK, many companies offer similar heatsinks but with longer fins. The typical 40mm heatsinks isn’t good enough when you know there’s better stuff out there. I even sent an exemple of such heatsinks with company info to Modushop and it went nowhere. Maybe Gianluca can look at this one more time.
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Holzarbeiter said:
Each builder has their own problems to solve. I will look into doubling up the sinks to get the height.
Esp when Modushop has their sales the problem is easier to decide.
If I can't get what I want I put metal on the Mill and solve it that way.
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Thanks for your feedback. As I've already specified in other threads it's not that we don't want to change our heatsinks or start selling new ones but the start up cost are incredibly high:

  • In order to have our supplier start producing new heatsinks for us we would need to a purchase a "mold" which costs 8000-10000 EUR
  • We would need to purchase at least 1000 KG PER MODEL per time

Is it worth it? Probably not. That's why I always suggest to stick to the ones we already have unless there is enough demand for new ones
 
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H

Holzarbeiter

Member
Joined 2014
Paid Member
Gianluca said:
start up cost are incredibly high:
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As a maschinest for 70 years, Olld School, people have no clue to the costs of CNC and their operators. I can get away with making anything I need. Since the 70's when gov'ts got involved in the supply chain it does not take much to break a small co.

If a company makes a part you can use buy it. If they can't, simple enough, look for another part or make it yourself and or modify it.
 
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Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
deleted long post....... even if I'm risking misunderstanding, here it is short - I have impression that Modushop Catalogue is much bigger than their income should allow.

In that, they have all my sympathies, ZM being all life devotee of really special wakoo'Talian technical history


Now, we can always dream of scenario where we can get (easy) what we want, but fact is - bigger problems (or just bigger wishes) are always solved simply with bigger stack of greenies
 
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