Thanks for advices . Actually I m very close to put 4x lme49990 instead of 3x . Why? Because I need to have 100R at the output of each one , for stability . So in this moment the output impedance is around 33,3R . It will be so much better with 25R 
) . Plus ,less noise , less distorsion , more power to output , 100 ma at least . Now it s 75 ma only . I must have a buffer in the front of the resistive attenuator , because the impedance there is only 1k . Now , about the discrete stage . I really want to see one with the performance of 3xlme49990 . Maybe those op amps are to good for that job , anyway .
) . Plus ,less noise , less distorsion , more power to output , 100 ma at least . Now it s 75 ma only . I must have a buffer in the front of the resistive attenuator , because the impedance there is only 1k . Now , about the discrete stage . I really want to see one with the performance of 3xlme49990 . Maybe those op amps are to good for that job , anyway .
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And about the power supply stage . There are many reasons to use a filter before the stabiliser . One is that it can be used only one filter and a lot of stabilisers after it . The second one is that those lme49610 are not included in a feedback loop , so the pssr is very poor . I can only hope that the first stage of the supply will improve a bit the pssr at high frequency .
calvin , I'm really sorry if you think that . If I'm not agree with your opinion , that's doesn't mean that I know everything . This means that I like more my solution , that's all , nothing more . I would appreciate much more your next ideas instead of a deep silence .
well , good luck to you too .
well , good luck to you too .
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ok , let s see what I can do . First , lme49610 can not give more than 250ma , so I can not move it on the first stage of power supply , where the current is much bigger . Next , the output impedance of the stabilisers . Usually there is a resistor between the reg and each audio input stage , in the range of 2,2R to 22R . Will be a difference in my case if the reg have a very very low ouput impedance, or 0,1R ? I don t think so . Of course when you have connected a lot of consumers on the same reg , this is a critical problem . I have everything supplied separately . That s what I think .
Now , about the discret op vs integrated one . Of course integrated op are good enough for audio , even the primitive , cheap one , like njm4580 or Ne5532 . A part like lme49990 , ad797 it s far away too good for audio. Once again , this is just what I think .
How can be explained otherwise a design like Aava used in Accuphase , or the use for the input stage of P7100 , a truly exceptional amplifier , a njm4580?
Actually my concern for the sound of lme49990 is close to zero . Of course it will sound well , there is no doubt about it.
I believe that the biggest limitation of lme49990 is the output current and the output impedance . 100 ohms and 30 ma , that s all . But using 4 , the output impedance is down to 25 ohms , and the output current is raised up to more than 120 ma .
That s good enough .
the board have a mistake , I already correct it .
Now , about the discret op vs integrated one . Of course integrated op are good enough for audio , even the primitive , cheap one , like njm4580 or Ne5532 . A part like lme49990 , ad797 it s far away too good for audio. Once again , this is just what I think .
How can be explained otherwise a design like Aava used in Accuphase , or the use for the input stage of P7100 , a truly exceptional amplifier , a njm4580?
Actually my concern for the sound of lme49990 is close to zero . Of course it will sound well , there is no doubt about it.
I believe that the biggest limitation of lme49990 is the output current and the output impedance . 100 ohms and 30 ma , that s all . But using 4 , the output impedance is down to 25 ohms , and the output current is raised up to more than 120 ma .
That s good enough .
the board have a mistake , I already correct it .
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