F4 power amplifier - Page 65

audionut · 4th June 2007, 12:16 AM

Would two BOSOZ's in series drive the F4 enough to power regular speakers as well as say, Aleph 30's

iwahn · 4th June 2007, 04:13 PM

How about using a couple of LM3875 as preamp? With one of them inverting it should be possible to run the F4 balanced. Maybe...

Iwahn

Zen Mod · 4th June 2007, 05:21 PM

Quote:

Originally posted by iwahn
How about using a couple of LM3875 as preamp? With one of them inverting it should be possible to run the F4 balanced. Maybe...

Iwahn

that can't be on par with F4

Russ White · 4th June 2007, 05:26 PM

Much better would be the LME49810... Just tie sink and source.

Variac · 15th June 2007, 07:42 AM

Nelson,
Since the F4 seems to exist , how about an actual photo of it?

GRollins · 15th June 2007, 01:00 PM

I thought all the First Watt product used the same chassis...assuming that the gears of my cognition have not stripped (no guarantees), it'll look the same as the other fellas.

Grey

Variac · 15th June 2007, 03:44 PM

I specifically asked because this one seems to need a LOT of heatsink- more than most of the previous amps I think? Members seem to be happiest with heatsinks that are almost 30x30 by 50 cm per channel I believe and that's a lot bigger than the typical First Watt chassis I think.

If in fact Nelson uses the same heatsinks as before, with their horizontal orientation, it shows that the requirements are not quite as onerous as implied..

PLus the face plate will look different....

steenoe · 15th June 2007, 04:49 PM

Quote:

Originally posted by Variac
I specifically asked because this one seems to need a LOT of heatsink- more than most of the previous amps I think? Members seem to be happiest with heatsinks that are almost 30x30 by 50 cm per channel I believe and that's a lot bigger than the typical First Watt chassis I think.

If in fact Nelson uses the same heatsinks as before, with their horizontal orientation, it shows that the requirements are not quite as onerous as implied..

PLus the face plate will look different....

As far as I recall the F4 actually dissipates a bit less than the usual SE/CCS amps from NP. Approx 80 watts per channel.
Usually this figure is 100 watts.

Steen

Jaac · 15th June 2007, 04:50 PM

Let's say 2 amps bias per SE channel bij 44 volt is 88 Watt in class A to dissipate in a heatsink. So lets see the specs for thermal resistance of a irfp240
Tj-c =0,83K/W, Tc-s = 0.24K/W 0,5 K/W for an isolation plate and lets put al six on one 0,3 K/W heatsink (200mm SK56 from fisher).
Thats 1,8K/W best for a single FET. Gives me a total of 3.37K/W from junction to ambient.
One FET dissipates 88/6 Watt multiplie that by the 3,37K/W gives 49,4 K above ambient for the junction temp.
I think or was it to quick and simple ??

Variac · 15th June 2007, 05:45 PM

That fiendish Nelson seems to design his projects to fit the case!
Actually I'll bet he figured that first Watt will probably never exceed 25w/ch class A and ordered the case from there..
Ok OK - I guess I now know what it will look like....

Best advice on the heatsinks was "Crank up the bias until its at max allowable temp" Then I guess you can measure the bias and decide if that's enough. There never seems to be "too much"

If not enough: mas heatsink.

4th June 2007, 05:26 PM	#644
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	Much better would be the LME49810... Just tie sink and source. __________________ Less pulp more juice Twisted Pear Audio.

15th June 2007, 07:42 AM	#645
Variac diyAudio Editor Join Date: Dec 2001 Location: San Francisco, USA	Nelson, Since the F4 seems to exist , how about an actual photo of it? __________________ 2013 Burning Amp Festival announced: Sunday, October 6th in S.F. We need Volunteers & sign-up's for what you're bringing!

15th June 2007, 03:44 PM	#647
Variac diyAudio Editor Join Date: Dec 2001 Location: San Francisco, USA	I specifically asked because this one seems to need a LOT of heatsink- more than most of the previous amps I think? Members seem to be happiest with heatsinks that are almost 30x30 by 50 cm per channel I believe and that's a lot bigger than the typical First Watt chassis I think. If in fact Nelson uses the same heatsinks as before, with their horizontal orientation, it shows that the requirements are not quite as onerous as implied.. PLus the face plate will look different.... __________________ 2013 Burning Amp Festival announced: Sunday, October 6th in S.F. We need Volunteers & sign-up's for what you're bringing!

15th June 2007, 04:50 PM	#649
Jaac diyAudio Member Join Date: Oct 2002 Location: Laren NH	Let's say 2 amps bias per SE channel bij 44 volt is 88 Watt in class A to dissipate in a heatsink. So lets see the specs for thermal resistance of a irfp240 Tj-c =0,83K/W, Tc-s = 0.24K/W 0,5 K/W for an isolation plate and lets put al six on one 0,3 K/W heatsink (200mm SK56 from fisher). Thats 1,8K/W best for a single FET. Gives me a total of 3.37K/W from junction to ambient. One FET dissipates 88/6 Watt multiplie that by the 3,37K/W gives 49,4 K above ambient for the junction temp. I think or was it to quick and simple ?? __________________ The right tool for the right job, a very nice Solarboat \|\| Ready for a groupbuy ? CLick

15th June 2007, 05:45 PM	#650
Variac diyAudio Editor Join Date: Dec 2001 Location: San Francisco, USA	That fiendish Nelson seems to design his projects to fit the case! Actually I'll bet he figured that first Watt will probably never exceed 25w/ch class A and ordered the case from there.. Ok OK - I guess I now know what it will look like.... Best advice on the heatsinks was "Crank up the bias until its at max allowable temp" Then I guess you can measure the bias and decide if that's enough. There never seems to be "too much" If not enough: mas heatsink. __________________ 2013 Burning Amp Festival announced: Sunday, October 6th in S.F. We need Volunteers & sign-up's for what you're bringing!


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4th June 2007, 12:16 AM	#641
audionut diyAudio Member Join Date: Jan 2002 Location: Cleveland ohio	Would two BOSOZ's in series drive the F4 enough to power regular speakers as well as say, Aleph 30's

4th June 2007, 04:13 PM	#642
iwahn diyAudio Member Join Date: Jun 2002 Location: norway	How about using a couple of LM3875 as preamp? With one of them inverting it should be possible to run the F4 balanced. Maybe... Iwahn

15th June 2007, 01:00 PM	#646
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	I thought all the First Watt product used the same chassis...assuming that the gears of my cognition have not stripped (no guarantees), it'll look the same as the other fellas. Grey

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