F5 power amplifier - Page 691

jackinnj · 2nd February 2010, 04:23 PM

Quote:

Originally Posted by cviller

I ordered some 2SJ618/2SK3497 from digikey, but I'll have to wait a while before I get them. I'm looking forward to play around with them - they are relatively new, so there is not much info on them on the forum.

Looks interesting -- forward conductance is nearly twice the IRF parts -- but input cap is a lot higher as well.

bear · 2nd February 2010, 04:25 PM

Post 6883 A Wayne... he shows heatsinks intended for LED lighting products... I'd not run fans myself, since they add noise to the room. One might get away with a squirrel cage blower running off a much much much slower (&quieter) motor, and ducted to run air up and along the fins. It doesn't take that much air to greatly improve the effective heat transfer... one could turn the thing on with a thermal switch too...

One could approximate their size by "unwrapping them" and figuring the thermals for a 3" high and X" wide heatsink of similar fin construction... probably still not enough heatsink.

_-_-bear

cviller · 2nd February 2010, 04:25 PM

Yeah, so I might not use two pairs for the F5s.

erpiii · 3rd February 2010, 04:45 AM

One could approximate their size by "unwrapping them" and figuring the thermals for a 3" high and X" wide heatsink of similar fin construction... probably still not enough heatsink.

_-_-bear[/QUOTE]

I'm trying to find out what the power dissipation is on those heat sinks... I know the highest output for one of the arrays that can go on that heat sink is 56 watts. So, if I can get some dissipation numbers on those arrays, then maybe some assumptions can be formulated. Does anyone have any figures on what the max dissipation is on the output devices in the F5 at around 25C?

AndrewT · 3rd February 2010, 11:20 AM

Quote:

Originally Posted by erpiii

Does anyone have any figures on what the max dissipation is on the output devices in the F5 at around 25C?

it's all in the pdf.
dissipated power = bias current times voltage across the FET.

erpiii · 3rd February 2010, 02:49 PM

HI Andrew!

Okay... I'll bite.

"the F5 is a push-pull ClassA amplifier that when biased to 1.3A can deliver ~2,6Apk of ClassA current to the load.

If the load is 8r0 then the maximum ClassA power is 27W ([2 * 1.3]^2 * 8 / 2)"

Andrew T.

"BTW,
27W is equivalent to 54Wpk. i.e. both are 20.8Vpk and 2.6Apk into 8r0."

Andrew T.

Does this mean both devices +/- are at 54Wpk? For a total of 108W per channel? Does that mean both channels would dissipate 108Wpk?

Mr Pass says that the F5 power consumption is 180W 8ohm @ 25W

How do these numbers relate?

AndrewT · 3rd February 2010, 03:52 PM

do you want output power to the load?
or
do you want dissipated power to the heatsink?
Don't confuse the two.

erpiii · 3rd February 2010, 04:15 PM

Quote:

Originally Posted by AndrewT

do you want output power to the load?
or
do you want dissipated power to the heatsink?
Don't confuse the two.

It would be the dissipated power to the heat sink... I'm trying to relate it to other heat sinks... If I can find out their dissipation as well.

AndrewT · 3rd February 2010, 04:18 PM

post6905 reminds one of the way to arrive at dissipation power.

chrismercurio · 06:30 AM

What happens when the output of an F5 is choke loaded (with a big @ss choke)?

I know the output impedance changes to whatever the parallel inductor is...but is a coupling cap (always) required as well?

Thanks in advance,

Chris

p.s. threads of interest that deal with similar questions:

Choke Loads for Zen/Aleph Amps
Choke Loaded Zen

2nd February 2010, 04:25 PM	#6902
bear expert in tautology diyAudio Member Join Date: Apr 2002 Location: New York State USA	Post 6883 A Wayne... he shows heatsinks intended for LED lighting products... I'd not run fans myself, since they add noise to the room. One might get away with a squirrel cage blower running off a much much much slower (&quieter) motor, and ducted to run air up and along the fins. It doesn't take that much air to greatly improve the effective heat transfer... one could turn the thing on with a thermal switch too... One could approximate their size by "unwrapping them" and figuring the thermals for a 3" high and X" wide heatsink of similar fin construction... probably still not enough heatsink. _-_-bear __________________ _-_-bear http://www.bearlabs.com [...2SJ74 Toshiba bogus asian parts - beware! ] -- Btw, I don't actually know anything, FYI --

4th February 2010, 06:21 AM	#6910
chrismercurio diyAudio Member Join Date: Aug 2006 Location: Silicon Valley	Choke Loading an F5 What happens when the output of an F5 is choke loaded (with a big @ss choke)? I know the output impedance changes to whatever the parallel inductor is...but is a coupling cap (always) required as well? Thanks in advance, Chris p.s. threads of interest that deal with similar questions: Choke Loads for Zen/Aleph Amps Choke Loaded Zen Last edited by chrismercurio; 4th February 2010 at 06:30 AM.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Rockford Fosgate Power 20001 bd amplifier power rating??	pachoorion	Car Audio	8	8th May 2011 10:49 PM
Power transformers versus amplifier output power..what is your option?	destroyer X	Solid State	38	9th May 2009 05:23 PM
McIntosh Power Amplifier Power Guard	johnnyrt	Solid State	2	23rd August 2007 10:22 PM
Output power for a power amplifier	Progg70	Solid State	33	10th September 2006 08:44 AM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality	MARAVILLASAUDIO	Class D	1	5th November 2004 04:06 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

2nd February 2010, 04:25 PM	#6903
cviller diyAudio Member Join Date: Dec 2005 Location: Copenhagen Blog Entries: 2	Yeah, so I might not use two pairs for the F5s.

3rd February 2010, 04:45 AM	#6904
erpiii diyAudio Member Join Date: Dec 2007 Location: Land of the Morlocks	One could approximate their size by "unwrapping them" and figuring the thermals for a 3" high and X" wide heatsink of similar fin construction... probably still not enough heatsink. _-_-bear[/QUOTE] I'm trying to find out what the power dissipation is on those heat sinks... I know the highest output for one of the arrays that can go on that heat sink is 56 watts. So, if I can get some dissipation numbers on those arrays, then maybe some assumptions can be formulated. Does anyone have any figures on what the max dissipation is on the output devices in the F5 at around 25C?

3rd February 2010, 02:49 PM	#6906
erpiii diyAudio Member Join Date: Dec 2007 Location: Land of the Morlocks	HI Andrew! Okay... I'll bite. "the F5 is a push-pull ClassA amplifier that when biased to 1.3A can deliver ~2,6Apk of ClassA current to the load. If the load is 8r0 then the maximum ClassA power is 27W ([2 * 1.3]^2 * 8 / 2)" Andrew T. "BTW, 27W is equivalent to 54Wpk. i.e. both are 20.8Vpk and 2.6Apk into 8r0." Andrew T. Does this mean both devices +/- are at 54Wpk? For a total of 108W per channel? Does that mean both channels would dissipate 108Wpk? Mr Pass says that the F5 power consumption is 180W 8ohm @ 25W How do these numbers relate?

3rd February 2010, 03:52 PM	#6907
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	do you want output power to the load? or do you want dissipated power to the heatsink? Don't confuse the two.

3rd February 2010, 04:18 PM	#6909
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	post6905 reminds one of the way to arrive at dissipation power.