A possible new method to enhance the enjoyment of Pass FE2022

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Then TTA004B. It is similar as KA992.

 

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The old school kid MJE350. It is very good. Even at 10Vrms output, it is still H2 dominant.

 

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The last candidate, D45H11. It is H2 dominant but with higher THD.

 

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The summarized effects of VAS on THD, H2 and H3 are in the pictures.
If the minimal THD is the goal, KA1381 is the best choice.
I would pick up MJE350 as the VAS transistor.

Few words about H2 phase. When KA992 is used as the VAS, the H2 phase varies from +81 to +89 degrees. It very close to what Mr. Pass' ideal H2 phase(+90). However, if MJE350 is used, H2 phase is -98 to -109, positive H2 phase. Other VAS' phase are far away from ideal.