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Old 6th May 2007, 09:20 AM   #1
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Default 150W mosfet final results

in this post i would like to
A) thank all the guys who bother to help me out with my problems
B)post my final results
C) welcome anybody else who is willing to work with me on this one
AAAAAA--- the thanks !!!!
Dr BORA for giving me the legend 4 for free it seems that i insulted this guy in some way ( i really didnt mean to ) but it all end up that i never managed to make things work even in the relation between us or the amp itshelf

carlos destroyer x who really tryied to help me but i lost both his help and friendship cause he thinks that i insulted dr Bora

nelson pass who at least read my mail but was to busy to bother with this ( i can understand that ....it wasnt an easy thing to do ) especially for busy person like NP....i thank him for trying any way ....

andrew t who didnt like this circuit any way but his theory approach seem to have some kind of meaning .....

and many others like sixteck steven from holland .... quasi (he is also greek ) who shared with me their opinion either good or not

BBBBBBB----- the results !!!!!
with the help and opinion of all these people the results are like this
1-legend 4-8 doesnt operate as is in voltage like 60-66vdc/rail
2- it can be modified but always something will be wrong with it like to much offset ....to much idle .... ocilation les balance ...temperature ....vas currents and goes on
3- resulting also that if you tolerate one of this things the amp will NOT stand any abuse like small pa application may work in carefull use
4- and most importand in rails arround 40-50 volts amp is working more than perfect ....... except power, quality and sonics are really nice ........

CCCCCCC -------the welcome

since my original request was
1-one amp that operates at 66+66/vdc rails
2-yet simple to make
3-with soa power arround 150w ready to be both used and abused in small pa application
4-since my rails are currently 62.5+62.5 volts
5- and since i have no design skills i welcome any body who wants to help me out finish this ..to work together and come up with solid results


thank you please notice attachment of original schematic
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Old 6th May 2007, 10:13 AM   #2
whoa is offline whoa  Hungary
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hi sakis,

this is a kind of amp design i've been looking for quite a long time
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Old 6th May 2007, 10:45 AM   #3
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Default Very good Mr. Sakis... this show me once more your Spartan courage.


You impressed me very much.

A figther...someone that defends your ideas till the last minute..if someone cut you in pieces...will receive a finger when finished his job.

Send regards to Maria.

Nothing blocked anymore.... please...no more discussions.

love, comprehension, cooperation, friendship and peace brother!

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 6th May 2007, 11:10 AM   #4
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Default thank you

carlos destroyer x for your kind words

i never had the intention to insult DR Bora may be smoke of burned mosfet or overdose of cafeine made my words look insulting .....

on the other hand will be much more good to gain a friend .....than an amplifier ....

amplifiers you get many .....but friends ??????
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Old 6th May 2007, 11:34 AM   #5
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Default So....you get one more friend back..use him and be happy


regards to your wife.

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 6th May 2007, 04:34 PM   #6
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Default just called in

to say that all sakis is saying is more or less what happent ....
ive had my share of burned mosfets loads of coffe and cigarets....to make legend 8 work at 66 volts .....

come up with simular results...we worked this together .....
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Old 6th May 2007, 05:52 PM   #7
geminni is offline geminni  Yugoslavia
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I am getting ready to make Legend with 2 pairs per channel and you made me wonder. Are you saying that this amp wont work?
I have suply of +-55 volts which is not in safe area and not in the area of voltage that makes Legend unstable....
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Old 7th May 2007, 07:38 AM   #8
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Default making the legend with 55+55

will bring you in to these problems

a) idle of recomended 100ma will be consumed all in vas stage and not in the all amplifier thus you will notice a bit of warm in the vas MJE340 but mosfets will run cold

b) expect ocilation coming from non existing miller cap on vas stage

c) you will probably need more than 1.5 volts to drive the amp

d) if you dont use source resistors in the out of every mosfet things are very critical ( resistors not included in original circuit)

e)with the formation of currents arrount vas and the all circuit if you abuse the amp in any way ( like trying to remove a plug while amp is operating or overdrive the input with more signal ) you are going to have your shelf a....

MOSFET BBQ!!!!!!!! BURNED MOSFETS ALL OVER

all your problems will be solved with 42+42 rails and expect arround 100W with 55+55 you can expect at least 150w but its not stable
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Old 7th May 2007, 07:52 AM   #9
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Default also very importand

if you use originall component lay out from dr Bora in this is used bc 556 this is working up to 40 volts for more transistors have to be 2n5401 ( difrent pins also ...keep in mind )
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Old 7th May 2007, 09:03 AM   #10
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Default DEAR GEMINI

in the original pcb lay out there is a drill for vas amplifier MJE 340 so this can be located orizonatlly and probably with a small heatsink ......

if you do this DO NOT !!!! use a metal screw this existing there will create even more ocilation on the vas stage better locate MJE 340 vertically or use a plastic screw ......
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