F5 power amplifier

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Zen Mod

Zen Mod

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Joined 2003
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Bksabath said:
While you here
what would be the efect of using mosfets with Ciss of about 2500 pf on F5
they came in TO3P packs which current wise is nice?

also dumb.....:D
o YEAH
Click to expand...

just turn on your own dumbness , and co-relate Ciss vs. xconductance vs. No. of needed mosfets vs. max allowable dissipation per device

piece of cake
 

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Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
Bksabath said:
.....

Xcnductance may go avay with more gain on decent pre
.....
Click to expand...

nope

you need to observe F5 in isolation

xconductance , considering OLG vs. CLG vs. feedback

generally-if you lack in xconductance of output sage , or if you have higher than desired capacitance of output stage , you can partially compensate that with increase of xconductance of input stage ...... and way to do that is to double No. of input Jfets
or just use 2SJ74P and 2SK170P ; all problems will be solved
 
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bobodioulasso

bobodioulasso

Member
Joined 2008
Speaker return sees heavy currents causing voltage drops on its path that are not welcome on the input ground.
No need of a speaker return on the pcb. Can be wired at main star ground, leaving input ground clean.
At least separate ouptut ground path from input ground path.
Same for qround side of decoupling caps. Not clean. They need to have their own path to ground.


I don't think miliampere would cause problems
Click to expand...
look at current flowing through R7, R8, R3 when output is near positive rail.
 
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C

camshaft

Member
Joined 2006
labjr said:
Would be interesting to see a rectangular board with outputs on both sides since about the best heatsink available in the states is from Heatsink USA and the deepest one they make is only 10 inches.

I did noticed the manual mentions mono blocks. Would it work well to have all the N channel devices on on side and the P channel devices on the other heatsink?
Click to expand...

6L6 said:
If you use a single sink, yes, but if you are willing to make a frame to hold more than one together, you have infinite depth. FWIW, the hifi2000 cases, at 400mm or bigger are all multiple heatsinks.



That's more of an issue with the layout of the PCB than anything else. It's one one the reasons Peter Daniel makes his PCB as small as possible, it actually gives you more choices with how things are mounted and gives more flexibility in what kind of sinks you use.
Click to expand...

I agree about the case length. Given how expensive heatsinks are, and for those of us who already have heatsinks it doesn't make sense to redesign the case just to fit a 12" long board if we already have 10" x 11" heatsinks. It would be nice to see the boards split somehow for those of us who will be building them as monoblocks (which I think quite a few will given the heat requirements). I realize telling me to "make your own boards then" is a valid response, but since I can't and would instead be happy to pay for them I thought I'd offer my input.

Thanks,
Austin
 
6L6

6L6

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Joined 2010
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camshaft said:
I agree about the case length. Given how expensive heatsinks are, and for those of us who already have heatsinks it doesn't make sense to redesign the case just to fit a 12" long board if we already have 10" x 11" heatsinks.
Click to expand...

It has always humored me how many people clone the FirstWatt designs using the long skinny boards. If you have ever seen the FirstWatt heatsinks in person, or a really good photo of them, you see why the boards are arranged like that.

But... with the heatsinks that are available to the DIY community, however, a smaller and more rectangular board is highly advantageous. You can still make a highly symmetrical board, but IMO smaller is actually better.
 
Bksabath

Bksabath

Banned
Joined 2007
6L6 said:
It has always humored me how many people clone the FirstWatt designs using the long skinny boards. If you have ever seen the FirstWatt heatsinks in person, or a really good photo of them, you see why the boards are arranged like that.

But... with the heatsinks that are available to the DIY community, however, a smaller and more rectangular board is highly advantageous. You can still make a highly symmetrical board, but IMO smaller is actually better.
Click to expand...

Most walid point my sinks are 300 wide as well.

Name a size and let's see what came up maybe Peter is or cna be coerched in to making one of his.

Another tought
I find PCB design quite relaxing and enjoiable (beats plaiing C&C) if others are thinking about having a crack at it there is a Totaly free no moneys needed program that is similar to the one I use if not better

Gogle up Design Spark
 
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