F4 power amplifier

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Zen Mod

Zen Mod

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Algar_emi said:
On the F2 schematic, there is a L1 choke just before R23-R26.

What was its value?

No reply for the transfo rating, any comments?
Click to expand...


that L Papa drew as self inductance of WWnd resistors ;

that xformer will have ~ 25V unloaded per leg ;

can you compare that with power consumptions and used voltage in each of F amps?
 
Algar_emi

Algar_emi

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So I got these results:

Power Needed:
stereo F1 need +24V at 200VA = 4A per channel = Plitron 057014201, 160VA, 2X18V, 4.44A
stereo F2 need +24V at 150VA =3.2A per channel= Plitron 047014201, 120VA, 2X18V, 3.33A
stereo F3 need +46V at 200VA =2.2A per channel= Plitron 057014201, 160VA, 2X18V, 4.44A
stereo F4 need +/-24V at 160VA = 3A per channel = Plitron 047014201, 120VA, 2X18V, 3.33A
 
vitalstates

vitalstates

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well here it is.....damned if it didn't work straight out of the box...I've been running it for about an hour being fed by my creative zen and it sounds good through the cheapo test(£4each) speakers...cold bias was no prob and dc set to zero no prob

can only get the fets to about 38degs so far...I think I was being over cautious by spreading them out on the sink..mmmmm
 

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Zen Mod

Zen Mod

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Algar_emi said:
So I got these results:

Power Needed:
stereo F1 need +24V at 200VA = 4A per channel = Plitron 057014201, 160VA, 2X18V, 4.44A
stereo F2 need +24V at 150VA =3.2A per channel= Plitron 047014201, 120VA, 2X18V, 3.33A
stereo F3 need +46V at 200VA =2.2A per channel= Plitron 057014201, 160VA, 2X18V, 4.44A
stereo F4 need +/-24V at 160VA = 3A per channel = Plitron 047014201, 120VA, 2X18V, 3.33A
Click to expand...


nope ; maybe I wasn't clear - sorry .

check that again ;

what I wrote are Voltages and power consumptions ;

you must increase wattages of xformer at least for 50% , looking at my post ........... even better - double wattage .

so :


stereo F1 +24V at 200VA - xformer min 300VA

stereo F2 +24V at 150VA xformer min 225VA

stereo F3 +46V at 200VA xformer min 300VA

stereo F4 +/- 24V at 160VA xformer min 240VA
 
Zen Mod

Zen Mod

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vitalstates said:
well here it is.....damned if it didn't work straight out of the box...I've been running it for about an hour being fed by my creative zen and it sounds good through the cheapo test(£4each) speakers...cold bias was no prob and dc set to zero no prob

can only get the fets to about 38degs so far...I think I was being over cautious by spreading them out on the sink..mmmmm
Click to expand...


;)

seems that you can squeeze two F4s on those heatsinks
 
J

jleaman

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vitalstates

vitalstates

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First thoughts on the F4...

I took it to a local meet of valve heads yesterday(Daniel in the lions den)...

The general concensus was that it was a bit clinical and sharp but in fairness the damned thing wouldn't warm up....sooooo

I upped the bias to 250mv and it got hot pdq....Without exception in about 10 minutes everybody was tapping their feet and all agreed it took on another personality, far more liquid and dare I say it ..far more valve like.

during the conversation somebody was swapping out a black gate from one of the amps and I casually asked its value.......
tee hee the F4 was put together for less than the price of 1 cap.......

I love it already and its only done about 20 hours..future looks rosy

Thanks Nelson

Regards

Ed
 
Magura

Magura

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vitalstates said:

I upped the bias to 250mv and it got hot pdq....Without exception in about 10 minutes everybody was tapping their feet and all agreed it took on another personality, far more liquid and dare I say it ..far more valve like.
Click to expand...


If you got the heatsink for it, you would get even more of what you obviously like by upping the bias even further. Another way to get the same result, but with less power and heatsink is to simply disconnect 1 FET from each bank and give them like 400mA each (or more if you have the heatsink for it). The upper limit for the devices is well over 3A each.

Magura :)
 
carpenter

carpenter

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Wow, excellent report, and wonderful suggestions... so, with a hefty water cooled heatsink, I could up the bias from 200 mA to what value?

Magura suggests that each power fet can handle 3 amps. Forgive my ignorance, but with 6 power fets, is that a combined total of 18 amps, or does the fact that it's push/pull make it 9 amps continuous. At any rate, that's a lot of transformer and one huge power supply!:D
 
Zen Mod

Zen Mod

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carpenter said:
Wow, excellent report, and wonderful suggestions... so, with a hefty water cooled heatsink, I could up the bias from 200 mA to what value?

Magura suggests that each power fet can handle 3 amps. Forgive my ignorance, but with 6 power fets, is that a combined total of 18 amps, or does the fact that it's push/pull make it 9 amps continuous. At any rate, that's a lot of transformer and one huge power supply!:D
Click to expand...





:rofl:

ya can't be serious ....... off course that that's 3A through each pair ;

that reminds me on one of my brilliant attempts when I tried to connect AC/DC feedback to LTP via xformer ........ which already have driver role


complicated to describe without picture , but believe me - that was brilliant idea !

:clown:
 
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