Hi,

Can someone tell me what heatsink rating i need, i will be running 30v +/- in the standard configuration, with one chip per heatsink. I have posted this question over at DIYAUDIO and i have been told it is impossible to get over 50W output in bridged config without overheating?

Although Russ and Brian spoke comforting words about the capability of driving 4 Ohm loads with the Sympatico, i still struggle with this. If you use the nationals design tool;

http://www.national.com/analog/audio/

The design tool gives a warning with 4 Ohm loads and the voltages reccomended by TP

heatsink ratings:
28 V rails/4 Ohm load= 0.72 C/W/chip (20-0-20 transf.)
30 V rails/4 Ohm load= 0.53 C/W/chip (22-0-22 transf.)
33 V rails/4 Ohm load= 0.30 C/W/chip (24-0-24 transf.)

with 8 Ohm loads everthing looks fine:

28 V rails/8 Ohm load= 2.13 C/W/chip (20-0-20 transf.)
30 V rails/8 Ohm load= 1.76 C/W/chip (22-0-22 transf.)
33 V rails/8 Ohm load= 1.33 C/W/chip (24-0-24 transf.)

Does this has to do with the fact that the design tool is for single ended set up and that balanced set ups are a whole different story when it comes to power dissipation?

Could anyone explain?


Gerard

Huge heatsink when using 33V rails (heatsink would measure 150x250x80)

Edited by user Tuesday, May 26, 2009 1:45:07 AM(UTC)  | Reason: Not specified

Yes that must be it. I Just had some problems with overheating in the past that made me a little paranoid. I will be using 8 Ohm speakers anyway, but just wanted to make sure i could use 4 Ohm in the future as well. I'll go for the heatsink rating Brian suggest and rest at peace with it.

Thanks,

Gerard