F6 distortion issue

[fabrice63]

Hi everyone ,

I had to "rebuild" my F6 lately ( change the output ) and give the psu more capacitance.

it turns out that the 2nd harmonic is higher than before , x 10 more , especially in the high , what could cause such rise ??

thanks for your idea 🙂

I made an comparison with my other amp , so speakers , Dac , cables , are ok

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[2 picoDumbs]

Differences in transconductance in the output devices.

More likely some sought of error.

 

[KevinHeem]

Same on both channels?

 

[fabrice63]

Yes , about the same on both channel , worse at the right channel .

i check several time , solder joint , components , connexions , and so on .

it's only the 2nd who is high, all other harmonics are low as before .

how to check the transconductance of an output at work ?


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[fabrice63]

I got one more question :

what if the two Mosfet of the same channel work at different temperature , say one at 30°C and one at 60 °C , their transconductance will be different , could this rise the 2d harmonic ?

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[2 picoDumbs]

Yes.

 

[fabrice63]

Thanks Pico , gonna dig that way 😉

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