Salas hotrodded blue DCB1 build

diyAudio Chief Moderator
Joined 2002
Paid Member
If you run it low CCS<100mA we are talking just 1W dissipation per Mosfet. But it has to sit in a rather cool place of the chassis not to receive heat from power tubes also, away from power amp's trafo fields as it will be carrying input signal. Don't allow more than 50C in the vicinity of its electrolytics in a closed warmed up box. Ambient temp has to be calculated to the Mez's sink estimations also. Mezmerize is a full preamp up to 6 inputs, are you going to integrate multi input capability to the tube amp as well? Coax signal wire for sure. Going for a full integrated? Then you surely need to examine some tube integrateds to see how they shield, route, ground, etc. Its a complex job, but done many times.
 
Big E,
I found a wonderful heatsink calculator for us laypersons. I don't speak engineerese.
Natural convection heat sink

I graphed the HS i referred to earlier for both 600mA (12W) and 200mA (4W)
You're going to need some BIG sinks for 600mA!
I guess I'll be running the VW Golf turbo (200mA) 10 Ohm version with my ordered HeatSinks.
This is without forced air circulation just convection cooling.

Ron
 

Attachments

  • 600mA heatsink.jpg
    600mA heatsink.jpg
    319.1 KB · Views: 348
  • 200mA heatsink.jpg
    200mA heatsink.jpg
    161.9 KB · Views: 325
:)That calculator is smarter than me. I could not get it to reproduce the values for the farnell heatsink, so I'm not using it. It did show a 25 degree rise over ambient for the farnell sink though. Which is fine.

The farnell sink is HUGE! 100 x 100! I could make an amp case out of 4 of them, but adding volume and rca's is problematic.

So what are people doing for a case for such an item? I'm thinking thick aluminum plates added to front and back sides, heavy aluminum floor with L brackets and a ventilated top.
 
Last edited:
diyAudio Chief Moderator
Joined 2002
Paid Member
Wanting 0.6A hot rod, what would you expect... 12W dissipation per rail constantly with a 15+15VAC Tx... Your box construction plan sounds good. You should use good thermal paste (even CPU special paste -non conductive-) between the Mosfets-their pads-sinks and then use again along the sink sides which will be bolted to the Alu chassis. Then between chassis plates meeting lines, so the whole thing is aided to act as a bonded thermal mass.
 
How much worse is orienting the fins horizontally instead of vertically? I'm not talking about the above photos, just a different way to do it.

can't tell, but they are enough for this hotrod version..

I have mine with the same orientation almost a year now with no problems ...

model is : fischer sk68 sa 75

:) How many did you score by now?

4 so far :D
 
Last edited:
Dimz.
I'd bet the fins don't even work past the 2nd fin. (no offense meant) I'm glad they are working well for you, and that's what counts.


How much worse is orienting the fins horizontally instead of vertically? I'm not talking about the above photos, just a different way to do it.

In that link I posted about the HS calculator, the author has some very good articles written about the functioning of HS.

Ron
 
Dimz.
I'd bet the fins don't even work past the 2nd fin. (no offense meant) I'm glad they are working well for you, and that's what counts.

In that link I posted about the HS calculator, the author has some very good articles written about the functioning of HS.

Ron


I know about the orientation (Basic Theory / bottom of page) and you are right ,

still I think that fischer cant be wrong with their measurements and published data ...
and ofcourse it works ...
 
DimZ,
I surely meant no disrespect to you. Again, I'm glad they work sufficiently for you.
What Fischer are you referring to? Edit; I see above.
Reading the application notes from you link, there is a figure of 70% effective, but that is with a heat source on the bottom, as it shows energy being radiated equally from both sides. Horizontal fin direction is rated at roughly 85%.
BigE asked the question, I was answering.

Now take Papa's F5 with the angled fins and that's a different story altogether.
Ron
 

Attachments

  • First Watt F5.jpg
    First Watt F5.jpg
    95.8 KB · Views: 304
Last edited: