The KSC2690A has superior linearity. If you are repairing a vintage amplifier where the C1124 was used as a driver transistor, the KSC2690A will reduce distortion. It also comes in the modern TO-126L package.
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| Substitute | Notes | |------------|-------| | 2SC3355 | Higher fT, lower noise, similar pinout (check first) | | 2SC2570 | Very similar, often direct drop-in | | MPSH10 | Slightly lower fT, but widely available | | BFR91 | For higher power applications | The KSC2690A has superior linearity