F5 power amplifier

So I'm finally almost ready to start putting together my F5, just waiting on delivery of a few of last parts and word of a turbo is now out. Do I continue and experience the original F5 and then modiify to a turbo or just wait and turbo from the start ?

If you don't build it both ways, how will you ever know if the Turbo is an improvement or not?

Roscoe
 
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F-5 to Turbo F-5 Rambling thoughts...

Want to build the Turbo version, but am in the middle of my second F-5 build now.
Mr Pass states that the standard F-5 can be converted, but I'm wondering what is involved in the change. Heatsinks are already drilled for Peter Daniels board spacing for the Toshiba Mosfets and the boards populated....would love to know what is involved with a "conversion" to turbo F-5 so I can either: 1.) finish this (2nd) F-5 regular style, or 2.) wait and retrofit it for Turbo.... Only time will tell!

I'm thinking if there is going to be a Pass board I will want one, so maybe the total restart is in order, or I could just redrill and tap the sinks for the to be announced Pass boards, or will the Turbo require more heatsink anyway? I'm going to wait until the smoke clears, shouldnt be that long.:cool: I know there are several of us in this "half built F-5 but now here's the Turbo version" funk, would Mr Pass tip his hat for us to know what is involved with conversion? Would be way appreciated! Otherwise, X-mas time isnt that far away.......

russellc
 
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It's a nice amp just is. Turbo needs more heatsink I think

I'm wondering this, if so I am going to complete my current F-5 build in the standard form, but when Mr Pass states it can be converted, I'm wondering if more sink would be required or not. Oh well X-mas time isnt that far away and a new version sounds more interesting anyway! Also wondering about transformer requirements as well.....

russellc
 
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I received some underground info

you'll need two 1K8W xformers , primary 1x115Vac ,secondaries 2x115Vac ;

that's the way for Papa to use 768 pcs of autoformers , he bought 15 years ago , as lot from mnfctrr

that's what I call Real Turbo

(count on 280W dissipation per channel , for turbo starter version , A/B class )

:devilr:
 
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Yes 240 V on the wall and we could go around industrial area and borow a few capacitors from the power factor corection cabinets.

Or maybe just wait for Crimbo and see what Papa got in store...

No mater how far I push it I know is going to blow my head off whit sometink so simple as P3.

Only 280 watts dissipation that wil get my heat sink to about 53C
 
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Official Court Jester
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one thing is sure - Nelson is Nelson ...... and his sense of humor is ........ Nelson's

(in other words - you can expect just anything )
 

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there is nothing wrong with adopting a different output bias for the F5.
The F5 is a Push-Pull ClassA amplifier that automatically transitions over to ClassAB if the peak current demanded by the load exceeds the ClassA limit
This change from ClassA to ClassAB will happen no matter what bias you set up. The bias current simply sets the limiting ClassA current capability.

Hi Andrew, I understood the amp can be run with less current which is what I will do. Nelson also said that distortion is already very low but with less current it will be somewhat higher. That is acceptable.

Can the 0.47 Ohm source resistors of the output MOSFETs be lowered to 0.33 or 0.22 ohm in that specific case (of lower current) or does that not change a thing ? I think I will have it idling at 0.3 to 0.6 A.

Thanks in advance, my knowledge of power amps is rusty to say the least. I want my F5 to be efficient for driving low impedance speakers (somewhat less than 4 Ohm) at moderate sound levels.
 
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